Current version from old git. Release 0.0.9

.gitignore

+.pioenvs
+.pio/libdeps
+.pio/build
+.vscode
+*.ino.cpp
+config.h
+config.hftstuttgart.h
+.project
+.cproject
+.settings

Ampel.h

+#ifndef AMPEL_H_INCLUDED
+#define AMPEL_H_INCLUDED
+/*****************************************************************
+ * Libraries                                                     *
+ *****************************************************************/
+#include "config.h"
+#ifndef MEASUREMENT_TIMESTEP
+#  error Missing config.h file. Please copy config.example.h to config.h.
+#endif
+#ifdef MQTT
+#  include "mqtt.h"
+#endif
+
+#include "util.h"
+#include "wifi_util.h"
+#include "co2_sensor.h"
+
+#ifdef HTTP
+#  include "web_server.h"
+#endif
+
+#include "led_effects.h"
+#include "csv_writer.h"
+
+#if defined(ESP8266)
+//allows sensor to be seen as SENSOR_ID.local, from the local network. For example : espd05cc9.local
+#  include <ESP8266mDNS.h>
+#elif defined(ESP32)
+#  include <ESPmDNS.h>
+#endif
+
+void keepServicesAlive();
+void checkFlashButton();
+
+#endif

Ampel.ino

+/***
+ *       ____ ___ ____       _                         _
+ *      / ___/ _ \___ \     / \   _ __ ___  _ __   ___| |
+ *     | |  | | | |__) |   / _ \ | '_ ` _ \| '_ \ / _ \ |
+ *     | |__| |_| / __/   / ___ \| | | | | | |_) |  __/ |
+ *      \____\___/_____| /_/__ \_\_| |_| |_| .__/ \___|_|         _
+ *     | | | |/ _|_   _| / ___|| |_ _   _| |_| |_ __ _  __ _ _ __| |_
+ *     | |_| | |_  | |   \___ \| __| | | | __| __/ _` |/ _` | '__| __|
+ *     |  _  |  _| | |    ___) | |_| |_| | |_| || (_| | (_| | |  | |_
+ *     |_| |_|_|   |_|   |____/ \__|\__,_|\__|\__\__, |\__,_|_|   \__|
+ *                                               |___/
+ */
+
+#include "Ampel.h"
+
+/*****************************************************************
+ * GPL License                                                   *
+ *****************************************************************/
+/*
+ * This file is part of the "CO2 Ampel" project (https://gitlab.rz.hft-stuttgart.de/otto/hft-stuttgart_co2_ampel)
+ * Copyright (c) 2020 HfT Stuttgart.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*****************************************************************
+ * Authors                                                       *
+ *****************************************************************/
+/*
+ * Eric Duminil
+ * Robert Otto
+ * Myriam Guedey
+ * Tobias Gabriel Erhart
+ * Jonas Stave
+ */
+
+/*****************************************************************
+ * Configuration                                                 *
+ *****************************************************************/
+/*
+ * Please define settings in 'config.h'.
+ * There's an example config file called 'config.example.h'.
+ * You can copy 'config.public.h' (stored in Git) to 'config.h' (not stored in Git),
+ * and define your credentials and parameters in 'config.h'.
+ */
+
+/*****************************************************************
+ * Setup                                                         *
+ *****************************************************************/
+void setup() {
+  LedEffects::setupOnBoardLED();
+  LedEffects::onBoardLEDOff();
+
+  Serial.begin(BAUDS);
+
+  pinMode(0, INPUT);  // Flash button (used for forced calibration)
+
+  LedEffects::setupRing();
+
+  sensor::initialize();
+
+  Serial.print(F("Sensor ID: "));
+  Serial.println(SENSOR_ID);
+  Serial.print(F("Board    : "));
+  Serial.println(BOARD);
+
+  // Try to connect to Wi-Fi
+  WiFiConnect(SENSOR_ID);
+
+  Serial.print(F("WiFi STATUS: "));
+  Serial.println(WiFi.status());
+
+  if (WiFi.status() == WL_CONNECTED) {
+#ifdef HTTP
+    web_server::initialize();
+#endif
+
+    ntp::initialize();
+
+    if (MDNS.begin(SENSOR_ID.c_str())) { // Start the mDNS responder for SENSOR_ID.local
+      MDNS.addService("http", "tcp", 80);
+      Serial.println(F("mDNS responder started"));
+    } else {
+      Serial.println(F("Error setting up MDNS responder!"));
+    }
+
+#ifdef MQTT
+    mqtt::initialize("CO2sensors/" + SENSOR_ID);
+#endif
+  }
+  csv_writer::initialize();
+}
+
+/*****************************************************************
+ * Main loop                                                     *
+ *****************************************************************/
+
+void loop() {
+  //NOTE: Loop should never take more than 1000ms. Split in smaller methods and logic if needed.
+  //TODO: Restart every day or week, in order to not let t0 overflow?
+  uint32_t t0 = millis();
+
+  /**
+   * USER INTERACTION
+   */
+  keepServicesAlive();
+  // Short press for night mode, Long press for calibration.
+  checkFlashButton();
+
+  /**
+   * GET DATA
+   */
+  bool freshData = sensor::scd30.dataAvailable(); // Alternative : close to time-step AND dataAvailable, to avoid asking the sensor too often.
+
+  if (freshData) {
+    sensor::co2 = sensor::scd30.getCO2();
+    sensor::temperature = sensor::scd30.getTemperature();
+    sensor::humidity = sensor::scd30.getHumidity();
+  }
+
+  //NOTE: Data is available, but it's sometimes erroneous: the sensor outputs zero ppm but non-zero temperature and non-zero humidity.
+  if (sensor::co2 <= 0) {
+    // No measurement yet. Waiting.
+    LedEffects::showWaitingLED(color::blue);
+    return;
+  }
+
+  /**
+   * Fresh data. Show it and send it if needed.
+   */
+
+  if (freshData) {
+    sensor::timestamp = ntp::getLocalTime();
+    Serial.println(sensor::timestamp);
+
+    Serial.print(F("co2(ppm): "));
+    Serial.print(sensor::co2);
+    Serial.print(F(" temp(C): "));
+    Serial.print(sensor::temperature);
+    Serial.print(F(" humidity(%): "));
+    Serial.println(sensor::humidity);
+
+    csv_writer::logIfTimeHasCome(sensor::timestamp, sensor::co2, sensor::temperature, sensor::humidity);
+
+#ifdef MQTT
+    mqtt::publishIfTimeHasCome(sensor::timestamp, sensor::co2, sensor::temperature, sensor::humidity);
+#endif
+  }
+
+  if (sensor::co2 < 250) {
+    // Sensor should be calibrated.
+    LedEffects::showWaitingLED(color::magenta);
+    return;
+  }
+
+  /**
+   * Display data, even if it's "old" (with breathing).
+   * Those effects include a short delay.
+   */
+
+  if (sensor::co2 < 2000) {
+    LedEffects::displayCO2color(sensor::co2);
+    LedEffects::breathe(sensor::co2);
+  } else {  // >= 2000: entire ring blinks red
+    LedEffects::redAlert();
+  }
+
+  uint32_t duration = millis() - t0;
+  if (duration > max_loop_duration) {
+    max_loop_duration = duration;
+    Serial.print("Max loop duration : ");
+    Serial.print(max_loop_duration);
+    Serial.println(" ms.");
+  }
+}
+
+/**
+ * Checks if flash button has been pressed:
+ *   If not, do nothing.
+ *   If short press, toggle LED display.
+ *   If long press, start calibration process.
+ */
+void checkFlashButton() {
+  if (!digitalRead(0)) { // Button has been pressed
+    LedEffects::onBoardLEDOn();
+    delay(300);
+    if (digitalRead(0)) {
+      Serial.println(F("Flash has been pressed for a short time. Should toggle night mode."));
+      LedEffects::toggleNightMode();
+    } else {
+      Serial.println(F("Flash has been pressed for a long time. Keep it pressed for calibration."));
+      if (LedEffects::countdownToZero() < 0) {
+        sensor::startCalibrationProcess();
+      }
+    }
+    LedEffects::onBoardLEDOff();
+  }
+}
+
+void keepServicesAlive() {
+  if (WiFi.status() == WL_CONNECTED) {
+#if defined(ESP8266)
+    //NOTE: Sadly, there seems to be a bug in the current MDNS implementation.
+    // It stops working after 2 minutes. And forcing a restart leads to a memory leak.
+    MDNS.update();
+#endif
+    ntp::update(); // NTP client has its own timer. It will connect to NTP server every 60s.
+#ifdef HTTP
+    web_server::update();
+#endif
+#ifdef MQTT
+    mqtt::keepConnection(); // MQTT client has its own timer. It will keep alive every 15s.
+#endif
+  }
+}

LICENSE

+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
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+
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+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.

Makefile

+all:
+	pio -f -c vim run
+
+upload:
+	pio -f -c vim run --target upload -e $(board)
+
+clean:
+	pio -f -c vim run --target clean
+
+program:
+	pio -f -c vim run --target program
+
+uploadfs:
+	pio -f -c vim run --target uploadfs
+
+update:
+	pio -f -c vim update
+
+monitor:
+	pio device monitor --filter colorize

README.md

+# CO<sub>2</sub> Ampel
+
+*CO<sub>2</sub> Ampel* is an open-source project, written in C++ for ESP8266 or ESP32.
+
+It measures the current CO<sub>2</sub> concentration (in ppm), and displays it on an LED ring.
+
+The room should be ventilated as soon as one LED turns red.
+
+## Hardware Requirements
+
+* [ESP8266](https://en.wikipedia.org/wiki/ESP8266) or [ESP32](https://en.wikipedia.org/wiki/ESP32) microcontroller (this project has been tested with *ESP8266 ESP-12 WIFI* and *TTGO ESP32 SX1276 LoRa*)
+* [Sensirion SCD30](https://www.sensirion.com/en/environmental-sensors/carbon-dioxide-sensors/carbon-dioxide-sensors-co2/) "Sensor Module for HVAC and Indoor Air Quality Applications"
+* [NeoPixel Ring - 12](https://www.adafruit.com/product/1643)
+
+## Software Requirements
+
+* [PlatformIO](https://platformio.org/)
+or
+* [Arduino IDE](https://www.arduino.cc/en/software)
+
+## Installation
+
+* If `config.h` does not exist, copy it from `config.public.h`
+* Modify `config.h`, e.g. for measurement time-steps, WiFi access, MQTT, NTP and web-server.
+
+### PlatformIO
+
+PlatformIO can be run from [VSCODE](https://platformio.org/install/ide?install=vscode), [Eclipse CDT](https://www.eclipse.org/cdt/) or console:
+
+```bash
+make upload board=esp8266 && make monitor # For ESP8266
+```
+```bash
+make upload board=esp32 && make monitor # For ESP32
+```
+
+### Arduino IDE
+
+* All the libraries are included in this repository. No need to install anything via *Library Manager*.
+
+* Add your board to the [board manager](https://github.com/esp8266/Arduino#installing-with-boards-manager). Either ESP8266:
+
+        http://arduino.esp8266.com/stable/package_esp8266com_index.json
+
+  or ESP32:
+
+        https://dl.espressif.com/dl/package_esp32_index.json
+
+* Choose the correct board in *Tools > Board > ...*
+* Choose the correct *Flash size* (e.g. "Flash Size : 4MB (1MB FS, OTA:~1019kB)" for *ESP8266 ESP-12 WIFI*)
+
+* *Verify*
+* *Upload*
+* *Tools > Serial Monitor*
+
+## Authors
+
+ * Eric Duminil
+ * Robert Otto
+ * Myriam Guedey
+ * Tobias Gabriel Erhart
+ * Jonas Stave
+
+Hochschule für Technik Stuttgart
+
+## Contributing
+Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.
+
+## License
+
+Copyright © 2020, [HfT Stuttgart](https://www.hft-stuttgart.de/)
+
+[GPLv3](https://choosealicense.com/licenses/gpl-3.0/)

co2_sensor.cpp

+#include "co2_sensor.h"
+
+namespace config {
+  // Values should be defined in config.h
+  uint16_t measurement_timestep = MEASUREMENT_TIMESTEP;  // [s] Value between 2 and 1800 (range for SCD30 sensor)
+  const uint16_t altitude_above_sea_level = ALTITUDE_ABOVE_SEA_LEVEL;  // [m]
+  uint16_t co2_calibration_level = ATMOSPHERIC_CO2_CONCENTRATION;  // [ppm]
+#ifdef TEMPERATURE_OFFSET
+  // Residual heat from CO2 sensor seems to be high enough to change the temperature reading. How much should it be offset?
+  // NOTE: Sign isn't relevant. The returned temperature will always be shifted down.
+  const float temperature_offset = TEMPERATURE_OFFSET;  // [K]
+#else
+  const float temperature_offset = -3.0;  // [K] Temperature measured by sensor is usually at least 3K too high.
+#endif
+  const bool auto_calibrate_sensor = AUTO_CALIBRATE_SENSOR;  // [true / false]
+}
+
+namespace sensor {
+  SCD30 scd30;
+  int16_t co2 = 0;
+  float temperature = 0;
+  float humidity = 0;
+  String timestamp = "";
+
+  void initialize() {
+#if defined(ESP8266)
+    Wire.begin(12, 14);  // ESP8266 - D6, D5;
+#endif
+#if defined(ESP32)
+    Wire.begin(21, 22);  // ESP32
+    /**
+     *  SCD30   ESP32
+     *  VCC --- 3V3
+     *  GND --- GND
+     *  SCL --- SCL (GPIO22) //NOTE: GPIO3 Would be more convenient (right next to GND)
+     *  SDA --- SDA (GPIO21) //NOTE: GPIO1 would be more convenient (right next to GPO3)
+     */
+#endif
+
+    // CO2
+    if (scd30.begin(config::auto_calibrate_sensor) == false) {
+      Serial.println("Air sensor not detected. Please check wiring. Freezing...");
+      while (1) {
+        LedEffects::showWaitingLED(color::red);
+      }
+    }
+
+    // SCD30 has its own timer.
+    Serial.println("\nSetting SCD30 timestep to " + String(config::measurement_timestep) + " s.");
+    scd30.setMeasurementInterval(config::measurement_timestep);  // [s]
+
+    Serial.print("Setting temperature offset to -");
+    Serial.print(abs(config::temperature_offset));
+    Serial.println(" K.");
+    scd30.setTemperatureOffset(abs(config::temperature_offset)); // setTemperatureOffset only accepts positive numbers, but shifts the temperature down.
+
+    Serial.print("Temperature offset is : -");
+    Serial.print(scd30.getTemperatureOffset());
+    Serial.println(" K");
+
+    Serial.print("Auto-calibration is ");
+    Serial.println(config::auto_calibrate_sensor ? "ON." : "OFF.");
+  }
+
+// Force SCD30 calibration with countdown.
+  void startCalibrationProcess() {
+    /** From the sensor documentation:
+     * For best results, the sensor has to be run in a stable environment in continuous mode at
+     * a measurement rate of 2s for at least two minutes before applying the FRC command and sending the reference value.
+     */
+    Serial.println("Setting SCD30 timestep to 2s, prior to calibration.");
+    scd30.setMeasurementInterval(2);  // [s] The change will only take effect after next measurement.
+    LedEffects::showKITTWheel(color::blue, config::measurement_timestep);
+    Serial.println("Waiting 2 minutes.");
+    LedEffects::showKITTWheel(color::blue, 120);
+    Serial.print("Starting SCD30 calibration...");
+    scd30.setAltitudeCompensation(config::altitude_above_sea_level);
+    scd30.setForcedRecalibrationFactor(config::co2_calibration_level);
+    Serial.println(" Done!");
+    Serial.println("Sensor calibrated.");
+    Serial.println("Sensor will now restart.");
+    LedEffects::showKITTWheel(color::green, 5);
+    FS_LIB.end();
+    ESP.restart();
+  }
+}

co2_sensor.h

+#ifndef CO2_SENSOR_H_
+#define CO2_SENSOR_H_
+
+// The SCD30 from Sensirion is a high quality Nondispersive Infrared (NDIR) based CO₂ sensor capable of detecting 400 to 10000ppm with an accuracy of ±(30ppm+3%).
+// https://github.com/sparkfun/SparkFun_SCD30_Arduino_Library
+#include "src/lib/SparkFun_SCD30_Arduino_Library/src/SparkFun_SCD30_Arduino_Library.h"  // From: http://librarymanager/All#SparkFun_SCD30
+#include "config.h"
+#include "led_effects.h"
+#include "csv_writer.h" // To close filesystem before restart.
+#include <Wire.h>
+
+namespace config {
+  extern uint16_t measurement_timestep;  // [s] Value between 2 and 1800 (range for SCD30 sensor)
+  extern const bool auto_calibrate_sensor; // [true / false]
+  extern uint16_t co2_calibration_level;  // [ppm]
+  extern const float temperature_offset; // [K] Sign isn't relevant.
+}
+
+namespace sensor {
+  extern SCD30 scd30;
+  extern int16_t co2;
+  extern float temperature;
+  extern float humidity;
+  extern String timestamp;
+
+  void initialize();
+  void startCalibrationProcess();
+}
+#endif

config.public.h

+#ifndef CONFIG_H_INCLUDED
+#  define CONFIG_H_INCLUDED
+
+// This file is a config template, and can be copied to config.h. Please don't save any important password in this template.
+
+/**
+ * WIFI
+ */
+
+// Setting WIFI_SSID to "NO_WIFI" will disable WiFi completely, and all other dependent services (MQTT, HTTP, NTP, ...)
+#  define WIFI_SSID     "NO_WIFI"
+#  define WIFI_PASSWORD "P4SSW0RD"
+#  define WIFI_TIMEOUT  20 // [s]
+
+/**
+ * Sensor
+ */
+
+// How often should measurement be performed, and displayed?
+//NOTE: SCD30 timer does not seem to be very precise. Variations may occur.
+#  define MEASUREMENT_TIMESTEP 60 // [s] Value between 2 and 1800 (range for SCD30 sensor)
+
+// How often measurements should be sent to MQTT server?
+// Probably a good idea to use a multiple of MEASUREMENT_TIMESTEP, so that averages can be calculated
+// Set to 0 if you want to send values after each measurement
+// #  define SENDING_INTERVAL MEASUREMENT_TIMESTEP * 5 // [s]
+#  define SENDING_INTERVAL 300 // [s]
+
+// How often should measurements be appended to CSV ?
+// Probably a good idea to use a multiple of MEASUREMENT_TIMESTEP, so that averages can be calculated
+// Set to 0 if you want to send values after each measurement
+#  define CSV_INTERVAL 300 // [s]
+
+// Residual heat from CO2 sensor seems to be high enough to change the temperature reading. How much should it be offset?
+// NOTE: Sign isn't relevant. The returned temperature will always be shifted down.
+#  define TEMPERATURE_OFFSET -3 // [K]
+
+// Altitude above sea level
+// Used for CO2 calibration
+// here: Stuttgart, Schellingstr. 24. (Source: Google Earth)
+#  define ALTITUDE_ABOVE_SEA_LEVEL 260 // [m]
+
+// The reference CO2 concentration has to be within the range 400 ppm ≤ cref(CO2) ≤ 2000 ppm.
+// Used for CO2 calibration
+// here : measured concentration in Stuttgart
+#  define ATMOSPHERIC_CO2_CONCENTRATION 425 // [ppm]
+
+// Should the sensor try to calibrate itself?
+// Sensirion recommends 7 days of continuous readings with at least 1 hour a day of 'fresh air' for self-calibration to complete.
+#  define AUTO_CALIBRATE_SENSOR true // [true / false]
+
+/**
+ * LEDs
+ */
+
+// LED brightness, which can vary between min and max brightness ("LED breathing")
+// max_brightness should be between 0 and 255.
+// min_brightness should be between 0 and max_brightness
+#  define MAX_BRIGHTNESS 255
+#  define MIN_BRIGHTNESS 60
+
+/**
+ * WEB SERVER
+ * available at http://local_ip, with user HTTP_USER and password HTTP_PASSWORD
+ */
+
+#  define HTTP // Comment or remove this line if you want to disable HTTP webserver
+
+// Define empty strings in order to disable authentication, or remove the constants altogether.
+#  define HTTP_USER "co2ampel"
+#  define HTTP_PASSWORD "my_password"
+
+/**
+ * MQTT SERVER
+ */
+#  define MQTT // Comment or remove this line if you want to disable MQTT
+
+/*
+ * If MQTT is enabled, co2ampel will publish data every SENDING_INTERVAL seconds.
+ * An MQTT subscriber can then get the data from the corresponding broker, either encrypted or unencrypted:
+ *
+ *  ❯ mosquitto_sub -h 'test.mosquitto.org' -p 8883 -t 'CO2sensors/#' --cafile mosquitto.org.crt -v
+ *  CO2sensors/ESPd05cc9 {"time":"2020-12-13 13:14:37+01", "co2":571, "temp":18.9, "rh":50.9}
+ *  CO2sensors/ESPd05cc9 {"time":"2020-12-13 13:14:48+01", "co2":573, "temp":18.9, "rh":50.2}
+ *  ...
+ *
+ *  ❯ mosquitto_sub -h 'test.mosquitto.org' -t 'CO2sensors/#' -v
+ *  CO2sensors/ESPd05cc9 {"time":"2020-12-13 13:15:09+01", "co2":568, "temp":18.9, "rh":50.1}
+ *  CO2sensors/ESPd05cc9 {"time":"2020-12-13 13:15:20+01", "co2":572, "temp":18.9, "rh":50.3}
+ *  ...
+ */
+
+/*
+ * Allow sensor to be configured over MQTT? Very useful for debugging. For example:
+ *   mosquitto_pub -h 'test.mosquitto.org' -t 'CO2sensors/ESPe08dc9/control' -m 'timer 30'
+ *   mosquitto_pub -h 'test.mosquitto.org' -t 'CO2sensors/ESPe08dc9/control' -m 'calibrate'
+ *   mosquitto_pub -h 'test.mosquitto.org' -t 'CO2sensors/ESPe08dc9/control' -m 'reset'
+ */
+#  define ALLOW_MQTT_COMMANDS false
+
+#  define MQTT_SERVER "test.mosquitto.org"  // MQTT server URL or IP address
+#  define MQTT_PORT 8883
+#  define MQTT_USER ""
+#  define MQTT_PASSWORD ""
+#  define MQTT_SERVER_FINGERPRINT "EE BC 4B F8 57 E3 D3 E4 07 54 23 1E F0 C8 A1 56 E0 D3 1A 1C" // SHA1 for test.mosquitto.org
+
+/**
+ * NTP
+ */
+
+#  define NTP_SERVER "pool.ntp.org"
+#  define UTC_OFFSET_IN_SECONDS 3600 // [s] 3600 for UTC+1
+
+/**
+ * Others
+ */
+#  define BAUDS 115200 // Transmission rate
+
+#endif

csv_writer.cpp

+#include "csv_writer.h"
+
+namespace config {
+  // Values should be defined in config.h
+  uint16_t csv_interval = CSV_INTERVAL; // [s]
+}
+namespace csv_writer {
+  unsigned long last_written_at = 0;
+  String last_successful_write = "";
+
+#if defined(ESP8266)
+  /**
+   * SPECIFIC FUNCTIONS FOR LITTLEFS
+   */
+  FSInfo fs_info;
+
+  bool mountFS() {
+    return LittleFS.begin(); // format if needed.
+  }
+
+  void updateFsInfo() {
+    FS_LIB.info(fs_info);
+  }
+
+  int getTotalSpace() {
+    return fs_info.totalBytes;
+  }
+
+  int getUsedSpace() {
+    return fs_info.usedBytes;
+  }
+
+  void showFilesystemContent() {
+    Dir dir = FS_LIB.openDir("/");
+    while (dir.next()) {
+      Serial.print("  ");
+      Serial.print(dir.fileName());
+      Serial.print(" - ");
+      if (dir.fileSize()) {
+        File f = dir.openFile("r");
+        Serial.println(f.size());
+        f.close();
+      } else {
+        Serial.println("0");
+      }
+    }
+  }
+#endif
+
+#if defined(ESP32)
+  /**
+   * SPECIFIC FUNCTIONS FOR SPIFFS
+   */
+  bool mountFS() {
+    return SPIFFS.begin(true); // format if needed.
+  }
+
+  void updateFsInfo() {
+    // Nothing to do.
+  }
+
+  int getTotalSpace() {
+    return SPIFFS.totalBytes();
+  }
+
+  int getUsedSpace() {
+    return SPIFFS.usedBytes();
+  }
+
+  void showFilesystemContent() {
+    File root = SPIFFS.open("/");
+    File file = root.openNextFile();
+    while (file) {
+      Serial.print("  ");
+      Serial.print(file.name());
+      Serial.print(" - ");
+      Serial.println(file.size());
+      file = root.openNextFile();
+    }
+  }
+#endif
+
+  const String filename = "/" + SENSOR_ID + ".csv";
+
+  int getAvailableSpace() {
+    //TODO : Check if too low?
+    return getTotalSpace() - getUsedSpace();
+  }
+
+  void initialize() {
+    Serial.print(F("Initializing FS..."));
+    if (mountFS()) {
+      Serial.println(F("done."));
+    } else {
+      Serial.println(F("fail."));
+      return;
+    }
+
+    updateFsInfo();
+
+    Serial.println(F("File system info:"));
+
+    Serial.print(F("  Total space    : "));
+    Serial.print(getTotalSpace() / 1024);
+    Serial.println("kB");
+
+    Serial.print(F("  Used space     : "));
+    Serial.print(getUsedSpace() / 1024);
+    Serial.println("kB");
+
+    Serial.print(F("  Available space: "));
+    Serial.print(getAvailableSpace() / 1024);
+    Serial.println("kB");
+    Serial.println();
+
+    // Open dir folder
+    Serial.println("Filesystem content:");
+    showFilesystemContent();
+
+    if (FS_LIB.exists(filename)) {
+      Serial.print(filename);
+      Serial.println(" has been found.");
+    }
+  }
+
+  File openOrCreate() {
+    File csv_file;
+    if (FS_LIB.exists(filename)) {
+      csv_file = FS_LIB.open(filename, "a+");
+    } else {
+      csv_file = FS_LIB.open(filename, "w");
+      csv_file.print(F("Sensor time;CO2 concentration;Temperature;Humidity\r\n"));
+      csv_file.print(F("YYYY-MM-DD HH:MM:SS+ZZ;ppm;degC;%\r\n"));
+    }
+    return csv_file;
+  }
+
+  void logIfTimeHasCome(const String &timeStamp, int16_t co2, float temp, float hum) {
+    unsigned long now = seconds();
+    //TODO: Write average since last CSV write?
+    if (now - last_written_at > config::csv_interval) {
+      last_written_at = now;
+      LedEffects::onBoardLEDOn();
+      File csv_file = openOrCreate();
+      char csv_line[42];
+      snprintf(csv_line, sizeof(csv_line), "%s;%d;%.1f;%.1f\r\n", timeStamp.c_str(), co2, temp, hum);
+      if (csv_file) {
+        size_t written_bytes = csv_file.print(csv_line);
+        csv_file.close();
+        if (written_bytes == 0) {
+          Serial.println(F("Nothing written. Disk full?"));
+        } else {
+          Serial.println(F("Wrote file content:"));
+          Serial.print(csv_line);
+          last_successful_write = ntp::getLocalTime();
+        }
+        updateFsInfo();
+        delay(50);
+      } else {
+        //NOTE: Can it ever happen that outfile is false?
+        Serial.println(F("Problem on create file!"));
+      }
+      LedEffects::onBoardLEDOff();
+    }
+  }
+}

csv_writer.h

+#ifndef CSV_WRITER_H_
+#define CSV_WRITER_H_
+
+#if defined(ESP8266)
+#  include <LittleFS.h>
+#  define FS_LIB LittleFS
+#elif defined(ESP32)
+#  include <SPIFFS.h>
+#  define FS_LIB SPIFFS
+#else
+#  error Board should be either ESP8266 or ESP832
+#endif
+
+#include "led_effects.h"
+#include "config.h"
+namespace config {
+  extern uint16_t csv_interval;  // [s]
+}
+namespace csv_writer {
+  extern String last_successful_write;
+  void initialize();
+  void logIfTimeHasCome(const String &timeStamp, int16_t co2, float temp, float hum);
+  int getAvailableSpace();
+  extern const String filename;
+}
+
+#endif

led_effects.cpp

+#include "led_effects.h"
+/*****************************************************************
+ * Configuration                                                 *
+ *****************************************************************/
+namespace config {
+  const uint8_t max_brightness = MAX_BRIGHTNESS;
+  const uint8_t min_brightness = MIN_BRIGHTNESS;
+  const int kitt_tail = 3; // How many dimmer LEDs follow in K.I.T.T. wheel
+}
+
+/*****************************************************************
+ * Configuration  (calculated from above values)                 *
+ *****************************************************************/
+namespace config  //TODO: Use a class instead. NightMode could then be another state.
+{
+  const float average_brightness = 0.5 * (config::max_brightness + config::min_brightness);
+  const float brightness_amplitude = 0.5 * (config::max_brightness - config::min_brightness);
+  bool night_mode = false;
+}
+
+// Adafruit NeoPixel (Arduino library for controlling single-wire-based LED pixels and strip)
+// https://github.com/adafruit/Adafruit_NeoPixel
+// Documentation : http://adafruit.github.io/Adafruit_NeoPixel/html/class_adafruit___neo_pixel.html
+
+// NeoPixels on GPIO05, aka D1 on ESP8266 or 5 on ESP32.
+const int NEOPIXELS_PIN = 5;
+const int NUMPIXELS = 12;
+//NOTE: One value has been prepended, to make calculations easier and avoid out of bounds index.
+const uint16_t CO2_TICKS[NUMPIXELS + 1] = { 0, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1600, 1800, 2000, 2200 }; // [ppm]
+// For a given LED, which color should be displayed? First LED will be pure green (hue angle 120°),
+// last 4 LEDs will be pure red (hue angle 0°), LEDs in-between will be yellowish.
+const uint16_t LED_HUES[NUMPIXELS] = { 21845, 19114, 16383, 13653, 10922, 8191, 5461, 2730, 0, 0, 0, 0 }; // [hue angle]
+Adafruit_NeoPixel pixels(NUMPIXELS, NEOPIXELS_PIN, NEO_GRB + NEO_KHZ800);
+
+namespace counter {
+  uint16_t wheel_offset = 0;
+  uint16_t kitt_offset = 0;
+  uint16_t breathing_offset = 0;
+}  // namespace counter
+
+namespace LedEffects {
+  //On-board LED on D4, aka GPIO02
+  const int ONBOARD_LED_PIN = 2;
+
+  void setupOnBoardLED() {
+    pinMode(ONBOARD_LED_PIN, OUTPUT);
+  }
+
+  void onBoardLEDOff() {
+    digitalWrite(ONBOARD_LED_PIN, HIGH);
+  }
+
+  void onBoardLEDOn() {
+    digitalWrite(ONBOARD_LED_PIN, LOW);
+  }
+
+  void setupRing() {
+    pixels.begin();
+    pixels.setBrightness(config::max_brightness);
+    pixels.clear();
+  }
+
+  void toggleNightMode() {
+    config::night_mode = !config::night_mode;
+    if (config::night_mode) {
+      Serial.println(F("NIGHT MODE!"));
+      pixels.clear();
+      pixels.show();
+    } else {
+      Serial.println(F("DAY MODE!"));
+    }
+  }
+
+  //NOTE: basically one iteration of KITT wheel
+  void showWaitingLED(uint32_t color) {
+    delay(80);
+    if (config::night_mode) {
+      return;
+    }
+    pixels.clear();
+    for (int j = config::kitt_tail; j >= 0; j--) {
+      int ledNumber = abs((counter::kitt_offset - j + NUMPIXELS) % (2 * NUMPIXELS) - NUMPIXELS) % NUMPIXELS; // Triangular function
+      pixels.setPixelColor(ledNumber, color * pixels.gamma8(255 - j * 76) / 255);
+    }
+    pixels.show();
+    counter::kitt_offset += 1;
+  }
+
+  // Start K.I.T.T. led effect. Red color as default.
+  // Simulate a moving LED with tail. First LED starts at 0, and moves along a triangular function. The tail follows, with decreasing brightness.
+  // Takes approximately 1s for each direction.
+  void showKITTWheel(uint32_t color, uint16_t duration_s) {
+    pixels.setBrightness(config::max_brightness);
+    for (int i = 0; i < duration_s * NUMPIXELS; ++i) {
+      showWaitingLED(color);
+    }
+  }
+
+  /*
+   * For a given CO2 level and ledId, which brightness should be displayed? 0 for off, 255 for on. Something in-between for partial LED.
+   * For example, for 1500ppm, every LED between 0 and 7 (500 -> 1400ppm) should be on, LED at 8 (1600ppm) should be half-on.
+   */
+  uint8_t getLedBrightness(uint16_t co2, int ledId) {
+    if (co2 >= CO2_TICKS[ledId + 1]) {
+      return 255;
+    } else {
+      if (2 * co2 >= CO2_TICKS[ledId] + CO2_TICKS[ledId + 1]) {
+        // Show partial LED if co2 more than halfway between ticks.
+        return 27; // Brightness isn't linear, so 27 / 255 looks much brighter than 10%
+      } else {
+        // LED off because co2 below previous tick
+        return 0;
+      }
+    }
+  }
+
+  /**
+   * Fills the whole ring with green, yellow, orange or black, depending on co2 input and CO2_TICKS.
+   */
+  void displayCO2color(uint16_t co2) {
+    if (config::night_mode) {
+      return;
+    }
+    pixels.setBrightness(config::max_brightness);
+    for (int ledId = 0; ledId < NUMPIXELS; ++ledId) {
+      uint8_t brightness = getLedBrightness(co2, ledId);
+      pixels.setPixelColor(ledId, pixels.ColorHSV(LED_HUES[ledId], 255, brightness));
+    }
+    pixels.show();
+  }
+
+  void showRainbowWheel(int duration_s, uint16_t hue_increment) {
+    if (config::night_mode) {
+      return;
+    }
+    unsigned long t0 = seconds();
+    pixels.setBrightness(config::max_brightness);
+    while (seconds() < t0 + duration_s) {
+      for (int i = 0; i < NUMPIXELS; i++) {
+        pixels.setPixelColor(i, pixels.ColorHSV(i * 65535 / NUMPIXELS + counter::wheel_offset));
+        counter::wheel_offset += hue_increment;
+      }
+      pixels.show();
+      delay(10);
+    }
+  }
+
+  void redAlert() {
+    if (config::night_mode) {
+      onBoardLEDOn();
+      delay(500);
+      onBoardLEDOff();
+      delay(500);
+      return;
+    }
+    for (int i = 0; i < 10; i++) {
+      pixels.setBrightness(static_cast<int>(config::max_brightness * (1 - i * 0.1)));
+      delay(50);
+      pixels.fill(color::red);
+      pixels.show();
+    }
+  }
+
+  void breathe(int16_t co2) {
+    if (!config::night_mode) {
+      //TODO: use integer sine
+      pixels.setBrightness(
+          static_cast<int>(config::average_brightness
+              + cos(counter::breathing_offset * 0.1) * config::brightness_amplitude));
+      pixels.show();
+      counter::breathing_offset += 1;
+    }
+    delay(co2 > 1600 ? 50 : 100);  // faster breathing for higher CO2 values
+  }
+
+  /**
+   * Displays a complete blue circle, and starts removing LEDs one by one. Returns the number of remaining LEDs.
+   * Can be used for calibration, e.g. when countdown is 0. Does not work in night mode.
+   */
+  int countdownToZero() {
+    if (config::night_mode) {
+      Serial.println("Night mode. Not doing anything.");
+      delay(1000); // Wait for a while, to avoid coming back to this function too many times when button is pressed.
+      return 1;
+    }
+    pixels.fill(color::blue);
+    pixels.show();
+    int countdown;
+    for (countdown = NUMPIXELS; countdown >= 0 && !digitalRead(0); countdown--) {
+      pixels.setPixelColor(countdown, color::black);
+      pixels.show();
+      Serial.println(countdown);
+      delay(500);
+    }
+    return countdown;
+  }
+}

led_effects.h

+#ifndef LED_EFFECTS_H_INCLUDED
+#define LED_EFFECTS_H_INCLUDED
+#include <Arduino.h>
+#include "util.h"
+#include "config.h"
+#include "src/lib/Adafruit_NeoPixel/Adafruit_NeoPixel.h"
+
+namespace color {
+  const uint32_t red = 0xFF0000;
+  const uint32_t green = 0x00FF00;
+  const uint32_t blue = 0x0000FF;
+  const uint32_t black = 0x000000;
+  const uint32_t magenta = 0xFF00FF;
+}
+
+namespace LedEffects {
+  void setupOnBoardLED();
+  void onBoardLEDOff();
+  void onBoardLEDOn();
+  void toggleNightMode();
+
+  void setupRing();
+  void redAlert();
+  void breathe(int16_t co2);
+  int countdownToZero();
+  void showWaitingLED(uint32_t color);
+  void showKITTWheel(uint32_t color, uint16_t duration_s = 2);
+  void showRainbowWheel(int duration_s = 1, uint16_t hue_increment = 50);
+  void displayCO2color(uint16_t co2);
+}
+#endif

mqtt.cpp

+#include "mqtt.h"
+
+namespace config {
+  // Values should be defined in config.h
+  uint16_t sending_interval = SENDING_INTERVAL; // [s]
+  //INFO: Listen to every CO2 sensor which is connected to the server:
+  //  mosquitto_sub -h MQTT_SERVER -t 'CO2sensors/#' -p 443 --capath /etc/ssl/certs/ -u "MQTT_USER" -P "MQTT_PASSWORD" -v
+  const char *mqtt_server = MQTT_SERVER;
+  const uint16_t mqtt_port = MQTT_PORT;
+  const char *mqtt_user = MQTT_USER;
+  const char *mqtt_password = MQTT_PASSWORD;
+  const char *fingerprint PROGMEM = MQTT_SERVER_FINGERPRINT;
+  const bool allow_mqtt_commands = ALLOW_MQTT_COMMANDS;
+  const unsigned long wait_after_fail = 900; // [s] Wait 15 minutes after an MQTT connection fail, before trying again.
+}
+#if defined(ESP32)
+#  include <WiFiClientSecure.h>
+#endif
+WiFiClientSecure espClient;
+PubSubClient mqttClient(espClient);
+
+namespace mqtt {
+  unsigned long last_sent_at = 0;
+  unsigned long last_failed_at = 0;
+
+  String publish_topic;
+  const char *json_sensor_format;
+  String last_successful_publish = "";
+
+  void initialize(String &topic) {
+    json_sensor_format = PSTR("{\"time\":\"%s\", \"co2\":%d, \"temp\":%.1f, \"rh\":%.1f}");
+    publish_topic = topic;
+#if defined(ESP8266)
+    espClient.setFingerprint(config::fingerprint); // not supported by ESP32
+#endif
+    // mqttClient.setSocketTimeout(config::mqtt_timeout); //NOTE: somehow doesn't seem to have any effect on connect()
+    mqttClient.setServer(config::mqtt_server, config::mqtt_port);
+  }
+
+  void publish(const String &timestamp, int16_t co2, float temperature, float humidity) {
+    if (WiFi.status() == WL_CONNECTED && mqttClient.connected()) {
+      LedEffects::onBoardLEDOn();
+      Serial.print(F("Publishing MQTT message ... "));
+
+      char payload[75]; // Should be enough for json...
+      snprintf(payload, sizeof(payload), json_sensor_format, timestamp.c_str(), co2, temperature, humidity);
+      // Topic is the same as clientID. e.g. 'CO2sensors/ESP3d03da'
+      if (mqttClient.publish(publish_topic.c_str(), payload)) {
+        Serial.println("OK");
+        last_successful_publish = ntp::getLocalTime();
+      } else {
+        Serial.println("Failed.");
+      }
+      LedEffects::onBoardLEDOff();
+    }
+  }
+
+  void setTimer(String messageString) {
+    messageString.replace("timer ", "");
+    int timestep = messageString.toInt();
+    if (timestep >= 2 && timestep <= 1800) {
+      Serial.print(F("Setting Measurement Interval to : "));
+      Serial.print(timestep);
+      Serial.println("s.");
+      sensor::scd30.setMeasurementInterval(messageString.toInt());
+      config::measurement_timestep = messageString.toInt();
+      LedEffects::showKITTWheel(color::green, 1);
+    }
+  }
+
+  void setMQTTinterval(String messageString) {
+    messageString.replace("mqtt ", "");
+    config::sending_interval = messageString.toInt();
+    Serial.print(F("Setting Sending Interval to : "));
+    Serial.print(config::sending_interval);
+    Serial.println("s.");
+    LedEffects::showKITTWheel(color::green, 1);
+  }
+
+  void setCSVinterval(String messageString) {
+    messageString.replace("csv ", "");
+    config::csv_interval = messageString.toInt();
+    Serial.print(F("Setting CSV Interval to : "));
+    Serial.print(config::csv_interval);
+    Serial.println("s.");
+    LedEffects::showKITTWheel(color::green, 1);
+  }
+
+  void calibrateSensor(String messageString) {
+    messageString.replace("calibrate ", "");
+    long int calibrationLevel = messageString.toInt();
+    if (calibrationLevel >= 400 && calibrationLevel <= 2000) {
+      Serial.print(F("Force calibration, at "));
+      config::co2_calibration_level = messageString.toInt();
+      Serial.print(config::co2_calibration_level);
+      Serial.println(" ppm.");
+      sensor::startCalibrationProcess();
+    }
+  }
+
+  void setCO2forDebugging(String messageString) {
+    Serial.print(F("DEBUG. Setting CO2 to "));
+    messageString.replace("co2 ", "");
+    sensor::co2 = messageString.toInt();
+    Serial.println(sensor::co2);
+  }
+
+  void sendInfoAboutLocalNetwork() {
+    char info_topic[60]; // Should be enough for "CO2sensors/ESPd05cc9/info"
+    snprintf(info_topic, sizeof(info_topic), "%s/info", publish_topic.c_str());
+
+    char payload[75]; // Should be enough for info json...
+    const char *json_info_format = PSTR("{\"local_ip\":\"%s\", \"ssid\":\"%s\"}");
+    snprintf(payload, sizeof(payload), json_info_format, WiFi.localIP().toString().c_str(), WiFi.SSID().c_str());
+
+    mqttClient.publish(info_topic, payload);
+  }
+
+  /**
+   * Allows sensor to be controlled by commands over MQTT
+   *
+   * mosquitto_pub -h MQTT_SERVER -t 'CO2sensors/SENSOR_ID/control' -p 443 --capath /etc/ssl/certs/ -u "MQTT_USER" -P "MQTT_PASSWORD" -m "reset"
+   * mosquitto_pub -h MQTT_SERVER -t 'CO2sensors/SENSOR_ID/control' -p 443 --capath /etc/ssl/certs/ -u "MQTT_USER" -P "MQTT_PASSWORD" -m "timer 30"
+   * mosquitto_pub -h MQTT_SERVER -t 'CO2sensors/SENSOR_ID/control' -p 443 --capath /etc/ssl/certs/ -u "MQTT_USER" -P "MQTT_PASSWORD" -m "mqtt 900"
+   * mosquitto_pub -h MQTT_SERVER -t 'CO2sensors/SENSOR_ID/control' -p 443 --capath /etc/ssl/certs/ -u "MQTT_USER" -P "MQTT_PASSWORD" -m "calibrate 700"
+   */
+  void controlSensorCallback(char *sub_topic, byte *message, unsigned int length) {
+    if (length == 0) {
+      return;
+    }
+    LedEffects::onBoardLEDOn();
+    Serial.print(F("Message arrived on topic: "));
+    Serial.print(sub_topic);
+    Serial.print(F(". Message: '"));
+    String messageString;
+    for (unsigned int i = 0; i < length; i++) {
+      Serial.print((char) message[i]);
+      messageString += (char) message[i];
+    }
+    Serial.println("'.");
+
+    if (messageString.startsWith("co2 ")) {
+      setCO2forDebugging(messageString);
+    } else if (messageString.startsWith("timer ")) {
+      setTimer(messageString);
+    } else if (messageString.startsWith("calibrate ")) {
+      calibrateSensor(messageString);
+//      config::atmospheric_co2_concentration
+    } else if (messageString.startsWith("mqtt ")) {
+      setMQTTinterval(messageString);
+    } else if (messageString.startsWith("csv ")) {
+      setCSVinterval(messageString);
+    } else if (messageString == "publish") {
+      Serial.println(F("Forcing MQTT publish now."));
+      publish(sensor::timestamp, sensor::co2, sensor::temperature, sensor::humidity);
+    } else if (messageString == "format_filesystem") {
+      FS_LIB.format();
+      LedEffects::showKITTWheel(color::blue, 2);
+    } else if (messageString == "night_mode") {
+      LedEffects::toggleNightMode();
+    } else if (messageString == "local_ip") {
+      sendInfoAboutLocalNetwork();
+    } else if (messageString == "reset") {
+      FS_LIB.end();
+      ESP.restart();
+    } else {
+      LedEffects::showKITTWheel(color::red, 1);
+      Serial.println(F("Message not supported. Doing nothing."));
+    }
+    delay(50);
+    LedEffects::onBoardLEDOff();
+  }
+
+  void reconnect() {
+    if (last_failed_at > 0 && seconds() - last_failed_at < config::wait_after_fail) {
+      // It failed less than wait_after_fail ago. Not even trying.
+      return;
+    }
+    if (WiFi.status() != WL_CONNECTED) { //NOTE: Sadly, WiFi.status is sometimes WL_CONNECTED even though it's really not
+      // No WIFI
+      return;
+    }
+    Serial.print(F("Attempting MQTT connection..."));
+
+    LedEffects::onBoardLEDOn();
+    // Wait for connection, at most 15s (default)
+    mqttClient.connect(publish_topic.c_str(), config::mqtt_user, config::mqtt_password);
+    LedEffects::onBoardLEDOff();
+
+    if (mqttClient.connected()) {
+      //TODO: Send local IP?
+      if (config::allow_mqtt_commands) {
+        char control_topic[60]; // Should be enough for "CO2sensors/ESPd05cc9/control"
+        snprintf(control_topic, sizeof(control_topic), "%s/control", publish_topic.c_str());
+        mqttClient.subscribe(control_topic);
+        mqttClient.setCallback(controlSensorCallback);
+      }
+      Serial.println(F(" Connected."));
+      last_failed_at = 0;
+    } else {
+      last_failed_at = seconds();
+      Serial.print(F(" Failed! Error code="));
+      Serial.print(mqttClient.state());
+      Serial.print(F(". Will try again in "));
+      Serial.print(config::wait_after_fail);
+      Serial.println("s.");
+    }
+  }
+
+  void publishIfTimeHasCome(const String &timeStamp, int16_t co2, float temp, float hum) {
+    // Send message via MQTT according to sending interval
+    unsigned long now = seconds();
+    //TODO: Send average since last MQTT message?
+    if (now - last_sent_at > config::sending_interval) {
+      last_sent_at = now;
+      publish(timeStamp, co2, temp, hum);
+    }
+  }
+
+  void keepConnection() {
+    // Keep MQTT connection
+    if (!mqttClient.connected()) {
+      reconnect();
+    }
+    mqttClient.loop();
+  }
+
+}

mqtt.h

+#ifndef MQTT_H_INCLUDED
+#define MQTT_H_INCLUDED
+
+#include <Arduino.h>
+#include "config.h"
+#include "led_effects.h"
+#include "csv_writer.h"
+#include "co2_sensor.h"
+#include "src/lib/PubSubClient/src/PubSubClient.h"
+#include "wifi_util.h"
+namespace config {
+  extern uint16_t sending_interval;  // [s]
+}
+namespace mqtt {
+  extern String last_successful_publish;
+  void initialize(String &topic);
+  void keepConnection();
+  void publishIfTimeHasCome(const String &timeStamp, int16_t co2, float temp, float hum);
+}
+#endif

platformio.ini

+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter, extra scripting
+;   Upload options: custom port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;
+; Please visit documentation for the other options and examples
+; http://docs.platformio.org/page/projectconf.html
+
+[platformio]
+src_dir = ./
+
+[env:esp8266]
+platform = espressif8266
+board = esp12e
+framework = arduino
+monitor_speed = 115200
+
+[env:esp32]
+platform = espressif32
+board = ttgo-lora32-v1
+framework = arduino
+monitor_speed = 115200

src/lib/Adafruit_NeoPixel/Adafruit_NeoPixel.cpp

+/*!
+ * @file Adafruit_NeoPixel.cpp
+ *
+ * @mainpage Arduino Library for driving Adafruit NeoPixel addressable LEDs,
+ * FLORA RGB Smart Pixels and compatible devicess -- WS2811, WS2812, WS2812B,
+ * SK6812, etc.
+ *
+ * @section intro_sec Introduction
+ *
+ * This is the documentation for Adafruit's NeoPixel library for the
+ * Arduino platform, allowing a broad range of microcontroller boards
+ * (most AVR boards, many ARM devices, ESP8266 and ESP32, among others)
+ * to control Adafruit NeoPixels, FLORA RGB Smart Pixels and compatible
+ * devices -- WS2811, WS2812, WS2812B, SK6812, etc.
+ *
+ * Adafruit invests time and resources providing this open source code,
+ * please support Adafruit and open-source hardware by purchasing products
+ * from Adafruit!
+ *
+ * @section author Author
+ *
+ * Written by Phil "Paint Your Dragon" Burgess for Adafruit Industries,
+ * with contributions by PJRC, Michael Miller and other members of the
+ * open source community.
+ *
+ * @section license License
+ *
+ * This file is part of the Adafruit_NeoPixel library.
+ *
+ * Adafruit_NeoPixel is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Adafruit_NeoPixel is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with NeoPixel. If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "Adafruit_NeoPixel.h"
+
+#if defined(TARGET_LPC1768)
+  #include <time.h>
+#endif
+
+#if defined(NRF52) || defined(NRF52_SERIES)
+#include "nrf.h"
+
+// Interrupt is only disabled if there is no PWM device available
+// Note: Adafruit Bluefruit nrf52 does not use this option
+//#define NRF52_DISABLE_INT
+#endif
+
+/*!
+  @brief   NeoPixel constructor when length, pin and pixel type are known
+           at compile-time.
+  @param   n  Number of NeoPixels in strand.
+  @param   p  Arduino pin number which will drive the NeoPixel data in.
+  @param   t  Pixel type -- add together NEO_* constants defined in
+              Adafruit_NeoPixel.h, for example NEO_GRB+NEO_KHZ800 for
+              NeoPixels expecting an 800 KHz (vs 400 KHz) data stream
+              with color bytes expressed in green, red, blue order per
+              pixel.
+  @return  Adafruit_NeoPixel object. Call the begin() function before use.
+*/
+Adafruit_NeoPixel::Adafruit_NeoPixel(uint16_t n, uint16_t p, neoPixelType t) :
+  begun(false), brightness(0), pixels(NULL), endTime(0) {
+  updateType(t);
+  updateLength(n);
+  setPin(p);
+}
+
+/*!
+  @brief   "Empty" NeoPixel constructor when length, pin and/or pixel type
+           are not known at compile-time, and must be initialized later with
+           updateType(), updateLength() and setPin().
+  @return  Adafruit_NeoPixel object. Call the begin() function before use.
+  @note    This function is deprecated, here only for old projects that
+           may still be calling it. New projects should instead use the
+           'new' keyword with the first constructor syntax (length, pin,
+           type).
+*/
+Adafruit_NeoPixel::Adafruit_NeoPixel() :
+#if defined(NEO_KHZ400)
+  is800KHz(true),
+#endif
+  begun(false), numLEDs(0), numBytes(0), pin(-1), brightness(0), pixels(NULL),
+  rOffset(1), gOffset(0), bOffset(2), wOffset(1), endTime(0) {
+}
+
+/*!
+  @brief   Deallocate Adafruit_NeoPixel object, set data pin back to INPUT.
+*/
+Adafruit_NeoPixel::~Adafruit_NeoPixel() {
+  free(pixels);
+  if(pin >= 0) pinMode(pin, INPUT);
+}
+
+/*!
+  @brief   Configure NeoPixel pin for output.
+*/
+void Adafruit_NeoPixel::begin(void) {
+  if(pin >= 0) {
+    pinMode(pin, OUTPUT);
+    digitalWrite(pin, LOW);
+  }
+  begun = true;
+}
+
+/*!
+  @brief   Change the length of a previously-declared Adafruit_NeoPixel
+           strip object. Old data is deallocated and new data is cleared.
+           Pin number and pixel format are unchanged.
+  @param   n  New length of strip, in pixels.
+  @note    This function is deprecated, here only for old projects that
+           may still be calling it. New projects should instead use the
+           'new' keyword with the first constructor syntax (length, pin,
+           type).
+*/
+void Adafruit_NeoPixel::updateLength(uint16_t n) {
+  free(pixels); // Free existing data (if any)
+
+  // Allocate new data -- note: ALL PIXELS ARE CLEARED
+  numBytes = n * ((wOffset == rOffset) ? 3 : 4);
+  if((pixels = (uint8_t *)malloc(numBytes))) {
+    memset(pixels, 0, numBytes);
+    numLEDs = n;
+  } else {
+    numLEDs = numBytes = 0;
+  }
+}
+
+/*!
+  @brief   Change the pixel format of a previously-declared
+           Adafruit_NeoPixel strip object. If format changes from one of
+           the RGB variants to an RGBW variant (or RGBW to RGB), the old
+           data will be deallocated and new data is cleared. Otherwise,
+           the old data will remain in RAM and is not reordered to the
+           new format, so it's advisable to follow up with clear().
+  @param   t  Pixel type -- add together NEO_* constants defined in
+              Adafruit_NeoPixel.h, for example NEO_GRB+NEO_KHZ800 for
+              NeoPixels expecting an 800 KHz (vs 400 KHz) data stream
+              with color bytes expressed in green, red, blue order per
+              pixel.
+  @note    This function is deprecated, here only for old projects that
+           may still be calling it. New projects should instead use the
+           'new' keyword with the first constructor syntax
+           (length, pin, type).
+*/
+void Adafruit_NeoPixel::updateType(neoPixelType t) {
+  bool oldThreeBytesPerPixel = (wOffset == rOffset); // false if RGBW
+
+  wOffset = (t >> 6) & 0b11; // See notes in header file
+  rOffset = (t >> 4) & 0b11; // regarding R/G/B/W offsets
+  gOffset = (t >> 2) & 0b11;
+  bOffset =  t       & 0b11;
+#if defined(NEO_KHZ400)
+  is800KHz = (t < 256);      // 400 KHz flag is 1<<8
+#endif
+
+  // If bytes-per-pixel has changed (and pixel data was previously
+  // allocated), re-allocate to new size. Will clear any data.
+  if(pixels) {
+    bool newThreeBytesPerPixel = (wOffset == rOffset);
+    if(newThreeBytesPerPixel != oldThreeBytesPerPixel) updateLength(numLEDs);
+  }
+}
+
+#if defined(ESP8266)
+// ESP8266 show() is external to enforce ICACHE_RAM_ATTR execution
+extern "C" void ICACHE_RAM_ATTR espShow(
+  uint16_t pin, uint8_t *pixels, uint32_t numBytes, uint8_t type);
+#elif defined(ESP32)
+extern "C" void espShow(
+  uint16_t pin, uint8_t *pixels, uint32_t numBytes, uint8_t type);
+#endif // ESP8266
+
+#if defined(K210) 
+#define KENDRYTE_K210 1
+#endif
+
+#if defined(KENDRYTE_K210)
+extern "C" void  k210Show(
+    uint8_t pin, uint8_t *pixels, uint32_t numBytes, boolean is800KHz);
+#endif //KENDRYTE_K210
+/*!
+  @brief   Transmit pixel data in RAM to NeoPixels.
+  @note    On most architectures, interrupts are temporarily disabled in
+           order to achieve the correct NeoPixel signal timing. This means
+           that the Arduino millis() and micros() functions, which require
+           interrupts, will lose small intervals of time whenever this
+           function is called (about 30 microseconds per RGB pixel, 40 for
+           RGBW pixels). There's no easy fix for this, but a few
+           specialized alternative or companion libraries exist that use
+           very device-specific peripherals to work around it.
+*/
+void Adafruit_NeoPixel::show(void) {
+
+  if(!pixels) return;
+
+  // Data latch = 300+ microsecond pause in the output stream. Rather than
+  // put a delay at the end of the function, the ending time is noted and
+  // the function will simply hold off (if needed) on issuing the
+  // subsequent round of data until the latch time has elapsed. This
+  // allows the mainline code to start generating the next frame of data
+  // rather than stalling for the latch.
+  while(!canShow());
+  // endTime is a private member (rather than global var) so that multiple
+  // instances on different pins can be quickly issued in succession (each
+  // instance doesn't delay the next).
+
+  // In order to make this code runtime-configurable to work with any pin,
+  // SBI/CBI instructions are eschewed in favor of full PORT writes via the
+  // OUT or ST instructions. It relies on two facts: that peripheral
+  // functions (such as PWM) take precedence on output pins, so our PORT-
+  // wide writes won't interfere, and that interrupts are globally disabled
+  // while data is being issued to the LEDs, so no other code will be
+  // accessing the PORT. The code takes an initial 'snapshot' of the PORT
+  // state, computes 'pin high' and 'pin low' values, and writes these back
+  // to the PORT register as needed.
+
+  // NRF52 may use PWM + DMA (if available), may not need to disable interrupt
+#if !( defined(NRF52) || defined(NRF52_SERIES) )
+  noInterrupts(); // Need 100% focus on instruction timing
+#endif
+
+#if defined(__AVR__)
+// AVR MCUs -- ATmega & ATtiny (no XMEGA) ---------------------------------
+
+  volatile uint16_t
+    i   = numBytes; // Loop counter
+  volatile uint8_t
+   *ptr = pixels,   // Pointer to next byte
+    b   = *ptr++,   // Current byte value
+    hi,             // PORT w/output bit set high
+    lo;             // PORT w/output bit set low
+
+  // Hand-tuned assembly code issues data to the LED drivers at a specific
+  // rate. There's separate code for different CPU speeds (8, 12, 16 MHz)
+  // for both the WS2811 (400 KHz) and WS2812 (800 KHz) drivers. The
+  // datastream timing for the LED drivers allows a little wiggle room each
+  // way (listed in the datasheets), so the conditions for compiling each
+  // case are set up for a range of frequencies rather than just the exact
+  // 8, 12 or 16 MHz values, permitting use with some close-but-not-spot-on
+  // devices (e.g. 16.5 MHz DigiSpark). The ranges were arrived at based
+  // on the datasheet figures and have not been extensively tested outside
+  // the canonical 8/12/16 MHz speeds; there's no guarantee these will work
+  // close to the extremes (or possibly they could be pushed further).
+  // Keep in mind only one CPU speed case actually gets compiled; the
+  // resulting program isn't as massive as it might look from source here.
+
+// 8 MHz(ish) AVR ---------------------------------------------------------
+#if (F_CPU >= 7400000UL) && (F_CPU <= 9500000UL)
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+
+    volatile uint8_t n1, n2 = 0;  // First, next bits out
+
+    // Squeezing an 800 KHz stream out of an 8 MHz chip requires code
+    // specific to each PORT register.
+
+    // 10 instruction clocks per bit: HHxxxxxLLL
+    // OUT instructions:              ^ ^    ^   (T=0,2,7)
+
+    // PORTD OUTPUT ----------------------------------------------------
+
+#if defined(PORTD)
+ #if defined(PORTB) || defined(PORTC) || defined(PORTF)
+    if(port == &PORTD) {
+ #endif // defined(PORTB/C/F)
+
+      hi = PORTD |  pinMask;
+      lo = PORTD & ~pinMask;
+      n1 = lo;
+      if(b & 0x80) n1 = hi;
+
+      // Dirty trick: RJMPs proceeding to the next instruction are used
+      // to delay two clock cycles in one instruction word (rather than
+      // using two NOPs). This was necessary in order to squeeze the
+      // loop down to exactly 64 words -- the maximum possible for a
+      // relative branch.
+
+      asm volatile(
+       "headD:"                   "\n\t" // Clk  Pseudocode
+        // Bit 7:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi
+        "mov  %[n2]   , %[lo]"    "\n\t" // 1    n2   = lo
+        "out  %[port] , %[n1]"    "\n\t" // 1    PORT = n1
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        "sbrc %[byte] , 6"        "\n\t" // 1-2  if(b & 0x40)
+         "mov %[n2]   , %[hi]"    "\n\t" // 0-1   n2 = hi
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        // Bit 6:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi
+        "mov  %[n1]   , %[lo]"    "\n\t" // 1    n1   = lo
+        "out  %[port] , %[n2]"    "\n\t" // 1    PORT = n2
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        "sbrc %[byte] , 5"        "\n\t" // 1-2  if(b & 0x20)
+         "mov %[n1]   , %[hi]"    "\n\t" // 0-1   n1 = hi
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        // Bit 5:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi
+        "mov  %[n2]   , %[lo]"    "\n\t" // 1    n2   = lo
+        "out  %[port] , %[n1]"    "\n\t" // 1    PORT = n1
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        "sbrc %[byte] , 4"        "\n\t" // 1-2  if(b & 0x10)
+         "mov %[n2]   , %[hi]"    "\n\t" // 0-1   n2 = hi
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        // Bit 4:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi
+        "mov  %[n1]   , %[lo]"    "\n\t" // 1    n1   = lo
+        "out  %[port] , %[n2]"    "\n\t" // 1    PORT = n2
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        "sbrc %[byte] , 3"        "\n\t" // 1-2  if(b & 0x08)
+         "mov %[n1]   , %[hi]"    "\n\t" // 0-1   n1 = hi
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        // Bit 3:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi
+        "mov  %[n2]   , %[lo]"    "\n\t" // 1    n2   = lo
+        "out  %[port] , %[n1]"    "\n\t" // 1    PORT = n1
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        "sbrc %[byte] , 2"        "\n\t" // 1-2  if(b & 0x04)
+         "mov %[n2]   , %[hi]"    "\n\t" // 0-1   n2 = hi
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        // Bit 2:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi
+        "mov  %[n1]   , %[lo]"    "\n\t" // 1    n1   = lo
+        "out  %[port] , %[n2]"    "\n\t" // 1    PORT = n2
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        "sbrc %[byte] , 1"        "\n\t" // 1-2  if(b & 0x02)
+         "mov %[n1]   , %[hi]"    "\n\t" // 0-1   n1 = hi
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        // Bit 1:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi
+        "mov  %[n2]   , %[lo]"    "\n\t" // 1    n2   = lo
+        "out  %[port] , %[n1]"    "\n\t" // 1    PORT = n1
+        "rjmp .+0"                "\n\t" // 2    nop nop
+        "sbrc %[byte] , 0"        "\n\t" // 1-2  if(b & 0x01)
+         "mov %[n2]   , %[hi]"    "\n\t" // 0-1   n2 = hi
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo
+        "sbiw %[count], 1"        "\n\t" // 2    i-- (don't act on Z flag yet)
+        // Bit 0:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi
+        "mov  %[n1]   , %[lo]"    "\n\t" // 1    n1   = lo
+        "out  %[port] , %[n2]"    "\n\t" // 1    PORT = n2
+        "ld   %[byte] , %a[ptr]+" "\n\t" // 2    b = *ptr++
+        "sbrc %[byte] , 7"        "\n\t" // 1-2  if(b & 0x80)
+         "mov %[n1]   , %[hi]"    "\n\t" // 0-1   n1 = hi
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo
+        "brne headD"              "\n"   // 2    while(i) (Z flag set above)
+      : [byte]  "+r" (b),
+        [n1]    "+r" (n1),
+        [n2]    "+r" (n2),
+        [count] "+w" (i)
+      : [port]   "I" (_SFR_IO_ADDR(PORTD)),
+        [ptr]    "e" (ptr),
+        [hi]     "r" (hi),
+        [lo]     "r" (lo));
+
+ #if defined(PORTB) || defined(PORTC) || defined(PORTF)
+    } else // other PORT(s)
+ #endif // defined(PORTB/C/F)
+#endif // defined(PORTD)
+
+    // PORTB OUTPUT ----------------------------------------------------
+
+#if defined(PORTB)
+ #if defined(PORTD) || defined(PORTC) || defined(PORTF)
+    if(port == &PORTB) {
+ #endif // defined(PORTD/C/F)
+
+      // Same as above, just switched to PORTB and stripped of comments.
+      hi = PORTB |  pinMask;
+      lo = PORTB & ~pinMask;
+      n1 = lo;
+      if(b & 0x80) n1 = hi;
+
+      asm volatile(
+       "headB:"                   "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 6"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 5"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 4"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 3"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 2"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 1"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 0"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "sbiw %[count], 1"        "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "ld   %[byte] , %a[ptr]+" "\n\t"
+        "sbrc %[byte] , 7"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "brne headB"              "\n"
+      : [byte] "+r" (b), [n1] "+r" (n1), [n2] "+r" (n2), [count] "+w" (i)
+      : [port] "I" (_SFR_IO_ADDR(PORTB)), [ptr] "e" (ptr), [hi] "r" (hi),
+        [lo] "r" (lo));
+
+ #if defined(PORTD) || defined(PORTC) || defined(PORTF)
+    }
+ #endif
+ #if defined(PORTC) || defined(PORTF)
+    else
+ #endif // defined(PORTC/F)
+#endif // defined(PORTB)
+
+    // PORTC OUTPUT ----------------------------------------------------
+
+#if defined(PORTC)
+ #if defined(PORTD) || defined(PORTB) || defined(PORTF)
+    if(port == &PORTC) {
+ #endif // defined(PORTD/B/F)
+
+      // Same as above, just switched to PORTC and stripped of comments.
+      hi = PORTC |  pinMask;
+      lo = PORTC & ~pinMask;
+      n1 = lo;
+      if(b & 0x80) n1 = hi;
+
+      asm volatile(
+       "headC:"                   "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 6"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 5"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 4"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 3"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 2"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 1"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 0"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "sbiw %[count], 1"        "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "ld   %[byte] , %a[ptr]+" "\n\t"
+        "sbrc %[byte] , 7"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "brne headC"              "\n"
+      : [byte] "+r" (b), [n1] "+r" (n1), [n2] "+r" (n2), [count] "+w" (i)
+      : [port] "I" (_SFR_IO_ADDR(PORTC)), [ptr] "e" (ptr), [hi] "r" (hi),
+        [lo] "r" (lo));
+
+ #if defined(PORTD) || defined(PORTB) || defined(PORTF)
+    }
+ #endif // defined(PORTD/B/F)
+ #if defined(PORTF)
+    else
+ #endif
+#endif // defined(PORTC)
+
+    // PORTF OUTPUT ----------------------------------------------------
+
+#if defined(PORTF)
+ #if defined(PORTD) || defined(PORTB) || defined(PORTC)
+    if(port == &PORTF) {
+ #endif // defined(PORTD/B/C)
+
+      hi = PORTF |  pinMask;
+      lo = PORTF & ~pinMask;
+      n1 = lo;
+      if(b & 0x80) n1 = hi;
+
+      asm volatile(
+       "headF:"                   "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 6"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 5"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 4"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 3"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 2"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 1"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n2]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n1]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "sbrc %[byte] , 0"        "\n\t"
+         "mov %[n2]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "sbiw %[count], 1"        "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "mov  %[n1]   , %[lo]"    "\n\t"
+        "out  %[port] , %[n2]"    "\n\t"
+        "ld   %[byte] , %a[ptr]+" "\n\t"
+        "sbrc %[byte] , 7"        "\n\t"
+         "mov %[n1]   , %[hi]"    "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "brne headF"              "\n"
+      : [byte] "+r" (b), [n1] "+r" (n1), [n2] "+r" (n2), [count] "+w" (i)
+      : [port] "I" (_SFR_IO_ADDR(PORTF)), [ptr] "e" (ptr), [hi] "r" (hi),
+        [lo] "r" (lo));
+
+ #if defined(PORTD) || defined(PORTB) || defined(PORTC)
+    }
+ #endif // defined(PORTD/B/C)
+#endif // defined(PORTF)
+
+#if defined(NEO_KHZ400)
+  } else { // end 800 KHz, do 400 KHz
+
+    // Timing is more relaxed; unrolling the inner loop for each bit is
+    // not necessary. Still using the peculiar RJMPs as 2X NOPs, not out
+    // of need but just to trim the code size down a little.
+    // This 400-KHz-datastream-on-8-MHz-CPU code is not quite identical
+    // to the 800-on-16 code later -- the hi/lo timing between WS2811 and
+    // WS2812 is not simply a 2:1 scale!
+
+    // 20 inst. clocks per bit: HHHHxxxxxxLLLLLLLLLL
+    // ST instructions:         ^   ^     ^          (T=0,4,10)
+
+    volatile uint8_t next, bit;
+
+    hi   = *port |  pinMask;
+    lo   = *port & ~pinMask;
+    next = lo;
+    bit  = 8;
+
+    asm volatile(
+     "head20:"                  "\n\t" // Clk  Pseudocode    (T =  0)
+      "st   %a[port], %[hi]"    "\n\t" // 2    PORT = hi     (T =  2)
+      "sbrc %[byte] , 7"        "\n\t" // 1-2  if(b & 128)
+       "mov  %[next], %[hi]"    "\n\t" // 0-1   next = hi    (T =  4)
+      "st   %a[port], %[next]"  "\n\t" // 2    PORT = next   (T =  6)
+      "mov  %[next] , %[lo]"    "\n\t" // 1    next = lo     (T =  7)
+      "dec  %[bit]"             "\n\t" // 1    bit--         (T =  8)
+      "breq nextbyte20"         "\n\t" // 1-2  if(bit == 0)
+      "rol  %[byte]"            "\n\t" // 1    b <<= 1       (T = 10)
+      "st   %a[port], %[lo]"    "\n\t" // 2    PORT = lo     (T = 12)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 14)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 16)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 18)
+      "rjmp head20"             "\n\t" // 2    -> head20 (next bit out)
+     "nextbyte20:"              "\n\t" //                    (T = 10)
+      "st   %a[port], %[lo]"    "\n\t" // 2    PORT = lo     (T = 12)
+      "nop"                     "\n\t" // 1    nop           (T = 13)
+      "ldi  %[bit]  , 8"        "\n\t" // 1    bit = 8       (T = 14)
+      "ld   %[byte] , %a[ptr]+" "\n\t" // 2    b = *ptr++    (T = 16)
+      "sbiw %[count], 1"        "\n\t" // 2    i--           (T = 18)
+      "brne head20"             "\n"   // 2    if(i != 0) -> (next byte)
+      : [port]  "+e" (port),
+        [byte]  "+r" (b),
+        [bit]   "+r" (bit),
+        [next]  "+r" (next),
+        [count] "+w" (i)
+      : [hi]    "r" (hi),
+        [lo]    "r" (lo),
+        [ptr]   "e" (ptr));
+  }
+#endif // NEO_KHZ400
+
+// 12 MHz(ish) AVR --------------------------------------------------------
+#elif (F_CPU >= 11100000UL) && (F_CPU <= 14300000UL)
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+
+    // In the 12 MHz case, an optimized 800 KHz datastream (no dead time
+    // between bytes) requires a PORT-specific loop similar to the 8 MHz
+    // code (but a little more relaxed in this case).
+
+    // 15 instruction clocks per bit: HHHHxxxxxxLLLLL
+    // OUT instructions:              ^   ^     ^     (T=0,4,10)
+
+    volatile uint8_t next;
+
+    // PORTD OUTPUT ----------------------------------------------------
+
+#if defined(PORTD)
+ #if defined(PORTB) || defined(PORTC) || defined(PORTF)
+    if(port == &PORTD) {
+ #endif // defined(PORTB/C/F)
+
+      hi   = PORTD |  pinMask;
+      lo   = PORTD & ~pinMask;
+      next = lo;
+      if(b & 0x80) next = hi;
+
+      // Don't "optimize" the OUT calls into the bitTime subroutine;
+      // we're exploiting the RCALL and RET as 3- and 4-cycle NOPs!
+      asm volatile(
+       "headD:"                   "\n\t" //        (T =  0)
+        "out   %[port], %[hi]"    "\n\t" //        (T =  1)
+        "rcall bitTimeD"          "\n\t" // Bit 7  (T = 15)
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeD"          "\n\t" // Bit 6
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeD"          "\n\t" // Bit 5
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeD"          "\n\t" // Bit 4
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeD"          "\n\t" // Bit 3
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeD"          "\n\t" // Bit 2
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeD"          "\n\t" // Bit 1
+        // Bit 0:
+        "out  %[port] , %[hi]"    "\n\t" // 1    PORT = hi    (T =  1)
+        "rjmp .+0"                "\n\t" // 2    nop nop      (T =  3)
+        "ld   %[byte] , %a[ptr]+" "\n\t" // 2    b = *ptr++   (T =  5)
+        "out  %[port] , %[next]"  "\n\t" // 1    PORT = next  (T =  6)
+        "mov  %[next] , %[lo]"    "\n\t" // 1    next = lo    (T =  7)
+        "sbrc %[byte] , 7"        "\n\t" // 1-2  if(b & 0x80) (T =  8)
+         "mov %[next] , %[hi]"    "\n\t" // 0-1    next = hi  (T =  9)
+        "nop"                     "\n\t" // 1                 (T = 10)
+        "out  %[port] , %[lo]"    "\n\t" // 1    PORT = lo    (T = 11)
+        "sbiw %[count], 1"        "\n\t" // 2    i--          (T = 13)
+        "brne headD"              "\n\t" // 2    if(i != 0) -> (next byte)
+         "rjmp doneD"             "\n\t"
+        "bitTimeD:"               "\n\t" //      nop nop nop     (T =  4)
+         "out  %[port], %[next]"  "\n\t" // 1    PORT = next     (T =  5)
+         "mov  %[next], %[lo]"    "\n\t" // 1    next = lo       (T =  6)
+         "rol  %[byte]"           "\n\t" // 1    b <<= 1         (T =  7)
+         "sbrc %[byte], 7"        "\n\t" // 1-2  if(b & 0x80)    (T =  8)
+          "mov %[next], %[hi]"    "\n\t" // 0-1   next = hi      (T =  9)
+         "nop"                    "\n\t" // 1                    (T = 10)
+         "out  %[port], %[lo]"    "\n\t" // 1    PORT = lo       (T = 11)
+         "ret"                    "\n\t" // 4    nop nop nop nop (T = 15)
+         "doneD:"                 "\n"
+        : [byte]  "+r" (b),
+          [next]  "+r" (next),
+          [count] "+w" (i)
+        : [port]   "I" (_SFR_IO_ADDR(PORTD)),
+          [ptr]    "e" (ptr),
+          [hi]     "r" (hi),
+          [lo]     "r" (lo));
+
+ #if defined(PORTB) || defined(PORTC) || defined(PORTF)
+    } else // other PORT(s)
+ #endif // defined(PORTB/C/F)
+#endif // defined(PORTD)
+
+    // PORTB OUTPUT ----------------------------------------------------
+
+#if defined(PORTB)
+ #if defined(PORTD) || defined(PORTC) || defined(PORTF)
+    if(port == &PORTB) {
+ #endif // defined(PORTD/C/F)
+
+      hi   = PORTB |  pinMask;
+      lo   = PORTB & ~pinMask;
+      next = lo;
+      if(b & 0x80) next = hi;
+
+      // Same as above, just set for PORTB & stripped of comments
+      asm volatile(
+       "headB:"                   "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeB"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeB"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeB"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeB"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeB"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeB"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeB"          "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "ld   %[byte] , %a[ptr]+" "\n\t"
+        "out  %[port] , %[next]"  "\n\t"
+        "mov  %[next] , %[lo]"    "\n\t"
+        "sbrc %[byte] , 7"        "\n\t"
+         "mov %[next] , %[hi]"    "\n\t"
+        "nop"                     "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "sbiw %[count], 1"        "\n\t"
+        "brne headB"              "\n\t"
+         "rjmp doneB"             "\n\t"
+        "bitTimeB:"               "\n\t"
+         "out  %[port], %[next]"  "\n\t"
+         "mov  %[next], %[lo]"    "\n\t"
+         "rol  %[byte]"           "\n\t"
+         "sbrc %[byte], 7"        "\n\t"
+          "mov %[next], %[hi]"    "\n\t"
+         "nop"                    "\n\t"
+         "out  %[port], %[lo]"    "\n\t"
+         "ret"                    "\n\t"
+         "doneB:"                 "\n"
+        : [byte] "+r" (b), [next] "+r" (next), [count] "+w" (i)
+        : [port] "I" (_SFR_IO_ADDR(PORTB)), [ptr] "e" (ptr), [hi] "r" (hi),
+          [lo] "r" (lo));
+
+ #if defined(PORTD) || defined(PORTC) || defined(PORTF)
+    }
+ #endif
+ #if defined(PORTC) || defined(PORTF)
+    else
+ #endif // defined(PORTC/F)
+#endif // defined(PORTB)
+
+    // PORTC OUTPUT ----------------------------------------------------
+
+#if defined(PORTC)
+ #if defined(PORTD) || defined(PORTB) || defined(PORTF)
+    if(port == &PORTC) {
+ #endif // defined(PORTD/B/F)
+
+      hi   = PORTC |  pinMask;
+      lo   = PORTC & ~pinMask;
+      next = lo;
+      if(b & 0x80) next = hi;
+
+      // Same as above, just set for PORTC & stripped of comments
+      asm volatile(
+       "headC:"                   "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "ld   %[byte] , %a[ptr]+" "\n\t"
+        "out  %[port] , %[next]"  "\n\t"
+        "mov  %[next] , %[lo]"    "\n\t"
+        "sbrc %[byte] , 7"        "\n\t"
+         "mov %[next] , %[hi]"    "\n\t"
+        "nop"                     "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "sbiw %[count], 1"        "\n\t"
+        "brne headC"              "\n\t"
+         "rjmp doneC"             "\n\t"
+        "bitTimeC:"               "\n\t"
+         "out  %[port], %[next]"  "\n\t"
+         "mov  %[next], %[lo]"    "\n\t"
+         "rol  %[byte]"           "\n\t"
+         "sbrc %[byte], 7"        "\n\t"
+          "mov %[next], %[hi]"    "\n\t"
+         "nop"                    "\n\t"
+         "out  %[port], %[lo]"    "\n\t"
+         "ret"                    "\n\t"
+         "doneC:"                 "\n"
+        : [byte] "+r" (b), [next] "+r" (next), [count] "+w" (i)
+        : [port] "I" (_SFR_IO_ADDR(PORTC)), [ptr] "e" (ptr), [hi] "r" (hi),
+          [lo] "r" (lo));
+
+ #if defined(PORTD) || defined(PORTB) || defined(PORTF)
+    }
+ #endif // defined(PORTD/B/F)
+ #if defined(PORTF)
+    else
+ #endif
+#endif // defined(PORTC)
+
+    // PORTF OUTPUT ----------------------------------------------------
+
+#if defined(PORTF)
+ #if defined(PORTD) || defined(PORTB) || defined(PORTC)
+    if(port == &PORTF) {
+ #endif // defined(PORTD/B/C)
+
+      hi   = PORTF |  pinMask;
+      lo   = PORTF & ~pinMask;
+      next = lo;
+      if(b & 0x80) next = hi;
+
+      // Same as above, just set for PORTF & stripped of comments
+      asm volatile(
+       "headF:"                   "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out   %[port], %[hi]"    "\n\t"
+        "rcall bitTimeC"          "\n\t"
+        "out  %[port] , %[hi]"    "\n\t"
+        "rjmp .+0"                "\n\t"
+        "ld   %[byte] , %a[ptr]+" "\n\t"
+        "out  %[port] , %[next]"  "\n\t"
+        "mov  %[next] , %[lo]"    "\n\t"
+        "sbrc %[byte] , 7"        "\n\t"
+         "mov %[next] , %[hi]"    "\n\t"
+        "nop"                     "\n\t"
+        "out  %[port] , %[lo]"    "\n\t"
+        "sbiw %[count], 1"        "\n\t"
+        "brne headF"              "\n\t"
+         "rjmp doneC"             "\n\t"
+        "bitTimeC:"               "\n\t"
+         "out  %[port], %[next]"  "\n\t"
+         "mov  %[next], %[lo]"    "\n\t"
+         "rol  %[byte]"           "\n\t"
+         "sbrc %[byte], 7"        "\n\t"
+          "mov %[next], %[hi]"    "\n\t"
+         "nop"                    "\n\t"
+         "out  %[port], %[lo]"    "\n\t"
+         "ret"                    "\n\t"
+         "doneC:"                 "\n"
+        : [byte] "+r" (b), [next] "+r" (next), [count] "+w" (i)
+        : [port] "I" (_SFR_IO_ADDR(PORTF)), [ptr] "e" (ptr), [hi] "r" (hi),
+          [lo] "r" (lo));
+
+ #if defined(PORTD) || defined(PORTB) || defined(PORTC)
+    }
+ #endif // defined(PORTD/B/C)
+#endif // defined(PORTF)
+
+#if defined(NEO_KHZ400)
+  } else { // 400 KHz
+
+    // 30 instruction clocks per bit: HHHHHHxxxxxxxxxLLLLLLLLLLLLLLL
+    // ST instructions:               ^     ^        ^    (T=0,6,15)
+
+    volatile uint8_t next, bit;
+
+    hi   = *port |  pinMask;
+    lo   = *port & ~pinMask;
+    next = lo;
+    bit  = 8;
+
+    asm volatile(
+     "head30:"                  "\n\t" // Clk  Pseudocode    (T =  0)
+      "st   %a[port], %[hi]"    "\n\t" // 2    PORT = hi     (T =  2)
+      "sbrc %[byte] , 7"        "\n\t" // 1-2  if(b & 128)
+       "mov  %[next], %[hi]"    "\n\t" // 0-1   next = hi    (T =  4)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T =  6)
+      "st   %a[port], %[next]"  "\n\t" // 2    PORT = next   (T =  8)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 10)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 12)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 14)
+      "nop"                     "\n\t" // 1    nop           (T = 15)
+      "st   %a[port], %[lo]"    "\n\t" // 2    PORT = lo     (T = 17)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 19)
+      "dec  %[bit]"             "\n\t" // 1    bit--         (T = 20)
+      "breq nextbyte30"         "\n\t" // 1-2  if(bit == 0)
+      "rol  %[byte]"            "\n\t" // 1    b <<= 1       (T = 22)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 24)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 26)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 28)
+      "rjmp head30"             "\n\t" // 2    -> head30 (next bit out)
+     "nextbyte30:"              "\n\t" //                    (T = 22)
+      "nop"                     "\n\t" // 1    nop           (T = 23)
+      "ldi  %[bit]  , 8"        "\n\t" // 1    bit = 8       (T = 24)
+      "ld   %[byte] , %a[ptr]+" "\n\t" // 2    b = *ptr++    (T = 26)
+      "sbiw %[count], 1"        "\n\t" // 2    i--           (T = 28)
+      "brne head30"             "\n"   // 1-2  if(i != 0) -> (next byte)
+      : [port]  "+e" (port),
+        [byte]  "+r" (b),
+        [bit]   "+r" (bit),
+        [next]  "+r" (next),
+        [count] "+w" (i)
+      : [hi]     "r" (hi),
+        [lo]     "r" (lo),
+        [ptr]    "e" (ptr));
+  }
+#endif // NEO_KHZ400
+
+// 16 MHz(ish) AVR --------------------------------------------------------
+#elif (F_CPU >= 15400000UL) && (F_CPU <= 19000000L)
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+
+    // WS2811 and WS2812 have different hi/lo duty cycles; this is
+    // similar but NOT an exact copy of the prior 400-on-8 code.
+
+    // 20 inst. clocks per bit: HHHHHxxxxxxxxLLLLLLL
+    // ST instructions:         ^   ^        ^       (T=0,5,13)
+
+    volatile uint8_t next, bit;
+
+    hi   = *port |  pinMask;
+    lo   = *port & ~pinMask;
+    next = lo;
+    bit  = 8;
+
+    asm volatile(
+     "head20:"                   "\n\t" // Clk  Pseudocode    (T =  0)
+      "st   %a[port],  %[hi]"    "\n\t" // 2    PORT = hi     (T =  2)
+      "sbrc %[byte],  7"         "\n\t" // 1-2  if(b & 128)
+       "mov  %[next], %[hi]"     "\n\t" // 0-1   next = hi    (T =  4)
+      "dec  %[bit]"              "\n\t" // 1    bit--         (T =  5)
+      "st   %a[port],  %[next]"  "\n\t" // 2    PORT = next   (T =  7)
+      "mov  %[next] ,  %[lo]"    "\n\t" // 1    next = lo     (T =  8)
+      "breq nextbyte20"          "\n\t" // 1-2  if(bit == 0) (from dec above)
+      "rol  %[byte]"             "\n\t" // 1    b <<= 1       (T = 10)
+      "rjmp .+0"                 "\n\t" // 2    nop nop       (T = 12)
+      "nop"                      "\n\t" // 1    nop           (T = 13)
+      "st   %a[port],  %[lo]"    "\n\t" // 2    PORT = lo     (T = 15)
+      "nop"                      "\n\t" // 1    nop           (T = 16)
+      "rjmp .+0"                 "\n\t" // 2    nop nop       (T = 18)
+      "rjmp head20"              "\n\t" // 2    -> head20 (next bit out)
+     "nextbyte20:"               "\n\t" //                    (T = 10)
+      "ldi  %[bit]  ,  8"        "\n\t" // 1    bit = 8       (T = 11)
+      "ld   %[byte] ,  %a[ptr]+" "\n\t" // 2    b = *ptr++    (T = 13)
+      "st   %a[port], %[lo]"     "\n\t" // 2    PORT = lo     (T = 15)
+      "nop"                      "\n\t" // 1    nop           (T = 16)
+      "sbiw %[count], 1"         "\n\t" // 2    i--           (T = 18)
+       "brne head20"             "\n"   // 2    if(i != 0) -> (next byte)
+      : [port]  "+e" (port),
+        [byte]  "+r" (b),
+        [bit]   "+r" (bit),
+        [next]  "+r" (next),
+        [count] "+w" (i)
+      : [ptr]    "e" (ptr),
+        [hi]     "r" (hi),
+        [lo]     "r" (lo));
+
+#if defined(NEO_KHZ400)
+  } else { // 400 KHz
+
+    // The 400 KHz clock on 16 MHz MCU is the most 'relaxed' version.
+
+    // 40 inst. clocks per bit: HHHHHHHHxxxxxxxxxxxxLLLLLLLLLLLLLLLLLLLL
+    // ST instructions:         ^       ^           ^         (T=0,8,20)
+
+    volatile uint8_t next, bit;
+
+    hi   = *port |  pinMask;
+    lo   = *port & ~pinMask;
+    next = lo;
+    bit  = 8;
+
+    asm volatile(
+     "head40:"                  "\n\t" // Clk  Pseudocode    (T =  0)
+      "st   %a[port], %[hi]"    "\n\t" // 2    PORT = hi     (T =  2)
+      "sbrc %[byte] , 7"        "\n\t" // 1-2  if(b & 128)
+       "mov  %[next] , %[hi]"   "\n\t" // 0-1   next = hi    (T =  4)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T =  6)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T =  8)
+      "st   %a[port], %[next]"  "\n\t" // 2    PORT = next   (T = 10)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 12)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 14)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 16)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 18)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 20)
+      "st   %a[port], %[lo]"    "\n\t" // 2    PORT = lo     (T = 22)
+      "nop"                     "\n\t" // 1    nop           (T = 23)
+      "mov  %[next] , %[lo]"    "\n\t" // 1    next = lo     (T = 24)
+      "dec  %[bit]"             "\n\t" // 1    bit--         (T = 25)
+      "breq nextbyte40"         "\n\t" // 1-2  if(bit == 0)
+      "rol  %[byte]"            "\n\t" // 1    b <<= 1       (T = 27)
+      "nop"                     "\n\t" // 1    nop           (T = 28)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 30)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 32)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 34)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 36)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 38)
+      "rjmp head40"             "\n\t" // 2    -> head40 (next bit out)
+     "nextbyte40:"              "\n\t" //                    (T = 27)
+      "ldi  %[bit]  , 8"        "\n\t" // 1    bit = 8       (T = 28)
+      "ld   %[byte] , %a[ptr]+" "\n\t" // 2    b = *ptr++    (T = 30)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 32)
+      "st   %a[port], %[lo]"    "\n\t" // 2    PORT = lo     (T = 34)
+      "rjmp .+0"                "\n\t" // 2    nop nop       (T = 36)
+      "sbiw %[count], 1"        "\n\t" // 2    i--           (T = 38)
+      "brne head40"             "\n"   // 1-2  if(i != 0) -> (next byte)
+      : [port]  "+e" (port),
+        [byte]  "+r" (b),
+        [bit]   "+r" (bit),
+        [next]  "+r" (next),
+        [count] "+w" (i)
+      : [ptr]    "e" (ptr),
+        [hi]     "r" (hi),
+        [lo]     "r" (lo));
+  }
+#endif // NEO_KHZ400
+
+#else
+ #error "CPU SPEED NOT SUPPORTED"
+#endif // end F_CPU ifdefs on __AVR__
+
+// END AVR ----------------------------------------------------------------
+
+
+#elif defined(__arm__)
+
+// ARM MCUs -- Teensy 3.0, 3.1, LC, Arduino Due ---------------------------
+
+#if defined(TEENSYDUINO) && defined(KINETISK) // Teensy 3.0, 3.1, 3.2, 3.5, 3.6
+#define CYCLES_800_T0H  (F_CPU / 4000000)
+#define CYCLES_800_T1H  (F_CPU / 1250000)
+#define CYCLES_800      (F_CPU /  800000)
+#define CYCLES_400_T0H  (F_CPU / 2000000)
+#define CYCLES_400_T1H  (F_CPU /  833333)
+#define CYCLES_400      (F_CPU /  400000)
+
+  uint8_t          *p   = pixels,
+                   *end = p + numBytes, pix, mask;
+  volatile uint8_t *set = portSetRegister(pin),
+                   *clr = portClearRegister(pin);
+  uint32_t          cyc;
+
+  ARM_DEMCR    |= ARM_DEMCR_TRCENA;
+  ARM_DWT_CTRL |= ARM_DWT_CTRL_CYCCNTENA;
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+    cyc = ARM_DWT_CYCCNT + CYCLES_800;
+    while(p < end) {
+      pix = *p++;
+      for(mask = 0x80; mask; mask >>= 1) {
+        while(ARM_DWT_CYCCNT - cyc < CYCLES_800);
+        cyc  = ARM_DWT_CYCCNT;
+        *set = 1;
+        if(pix & mask) {
+          while(ARM_DWT_CYCCNT - cyc < CYCLES_800_T1H);
+        } else {
+          while(ARM_DWT_CYCCNT - cyc < CYCLES_800_T0H);
+        }
+        *clr = 1;
+      }
+    }
+    while(ARM_DWT_CYCCNT - cyc < CYCLES_800);
+#if defined(NEO_KHZ400)
+  } else { // 400 kHz bitstream
+    cyc = ARM_DWT_CYCCNT + CYCLES_400;
+    while(p < end) {
+      pix = *p++;
+      for(mask = 0x80; mask; mask >>= 1) {
+        while(ARM_DWT_CYCCNT - cyc < CYCLES_400);
+        cyc  = ARM_DWT_CYCCNT;
+        *set = 1;
+        if(pix & mask) {
+          while(ARM_DWT_CYCCNT - cyc < CYCLES_400_T1H);
+        } else {
+          while(ARM_DWT_CYCCNT - cyc < CYCLES_400_T0H);
+        }
+        *clr = 1;
+      }
+    }
+    while(ARM_DWT_CYCCNT - cyc < CYCLES_400);
+  }
+#endif // NEO_KHZ400
+
+#elif defined(TEENSYDUINO) && (defined(__IMXRT1052__) || defined(__IMXRT1062__))
+#define CYCLES_800_T0H  (F_CPU_ACTUAL / 4000000)
+#define CYCLES_800_T1H  (F_CPU_ACTUAL / 1250000)
+#define CYCLES_800      (F_CPU_ACTUAL /  800000)
+#define CYCLES_400_T0H  (F_CPU_ACTUAL / 2000000)
+#define CYCLES_400_T1H  (F_CPU_ACTUAL /  833333)
+#define CYCLES_400      (F_CPU_ACTUAL /  400000)
+
+  uint8_t           *p   = pixels,
+                    *end = p + numBytes, pix, mask;
+  volatile uint32_t *set = portSetRegister(pin),
+                    *clr = portClearRegister(pin);
+  uint32_t          cyc,
+                    msk = digitalPinToBitMask(pin);
+
+  ARM_DEMCR    |= ARM_DEMCR_TRCENA;
+  ARM_DWT_CTRL |= ARM_DWT_CTRL_CYCCNTENA;
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+    cyc = ARM_DWT_CYCCNT + CYCLES_800;
+    while(p < end) {
+      pix = *p++;
+      for(mask = 0x80; mask; mask >>= 1) {
+        while(ARM_DWT_CYCCNT - cyc < CYCLES_800);
+        cyc  = ARM_DWT_CYCCNT;
+        *set = msk;
+        if(pix & mask) {
+          while(ARM_DWT_CYCCNT - cyc < CYCLES_800_T1H);
+        } else {
+          while(ARM_DWT_CYCCNT - cyc < CYCLES_800_T0H);
+        }
+        *clr = msk;
+      }
+    }
+    while(ARM_DWT_CYCCNT - cyc < CYCLES_800);
+#if defined(NEO_KHZ400)
+  } else { // 400 kHz bitstream
+    cyc = ARM_DWT_CYCCNT + CYCLES_400;
+    while(p < end) {
+      pix = *p++;
+      for(mask = 0x80; mask; mask >>= 1) {
+        while(ARM_DWT_CYCCNT - cyc < CYCLES_400);
+        cyc  = ARM_DWT_CYCCNT;
+        *set = msk;
+        if(pix & mask) {
+          while(ARM_DWT_CYCCNT - cyc < CYCLES_400_T1H);
+        } else {
+          while(ARM_DWT_CYCCNT - cyc < CYCLES_400_T0H);
+        }
+        *clr = msk;
+      }
+    }
+    while(ARM_DWT_CYCCNT - cyc < CYCLES_400);
+  }
+#endif // NEO_KHZ400
+
+#elif defined(TEENSYDUINO) && defined(__MKL26Z64__) // Teensy-LC
+
+#if F_CPU == 48000000
+  uint8_t          *p   = pixels,
+                    pix, count, dly,
+                    bitmask = digitalPinToBitMask(pin);
+  volatile uint8_t *reg = portSetRegister(pin);
+  uint32_t          num = numBytes;
+  asm volatile(
+    "L%=_begin:"                      "\n\t"
+     "ldrb  %[pix], [%[p], #0]"       "\n\t"
+     "lsl   %[pix], #24"              "\n\t"
+     "movs  %[count], #7"             "\n\t"
+    "L%=_loop:"                       "\n\t"
+     "lsl   %[pix], #1"               "\n\t"
+     "bcs   L%=_loop_one"             "\n\t"
+     "L%=_loop_zero:"                 "\n\t"
+     "strb  %[bitmask], [%[reg], #0]" "\n\t"
+     "movs  %[dly], #4"               "\n\t"
+    "L%=_loop_delay_T0H:"             "\n\t"
+     "sub   %[dly], #1"               "\n\t"
+     "bne   L%=_loop_delay_T0H"       "\n\t"
+     "strb  %[bitmask], [%[reg], #4]" "\n\t"
+     "movs  %[dly], #13"              "\n\t"
+    "L%=_loop_delay_T0L:"             "\n\t"
+     "sub   %[dly], #1"               "\n\t"
+     "bne   L%=_loop_delay_T0L"       "\n\t"
+     "b     L%=_next"                 "\n\t"
+    "L%=_loop_one:"                   "\n\t"
+     "strb  %[bitmask], [%[reg], #0]" "\n\t"
+     "movs  %[dly], #13"              "\n\t"
+    "L%=_loop_delay_T1H:"             "\n\t"
+     "sub   %[dly], #1"               "\n\t"
+     "bne   L%=_loop_delay_T1H"       "\n\t"
+     "strb  %[bitmask], [%[reg], #4]" "\n\t"
+     "movs  %[dly], #4"               "\n\t"
+    "L%=_loop_delay_T1L:"             "\n\t"
+     "sub   %[dly], #1"               "\n\t"
+     "bne   L%=_loop_delay_T1L"       "\n\t"
+     "nop"                            "\n\t"
+    "L%=_next:"                       "\n\t"
+     "sub   %[count], #1"             "\n\t"
+     "bne   L%=_loop"                 "\n\t"
+     "lsl   %[pix], #1"               "\n\t"
+     "bcs   L%=_last_one"             "\n\t"
+    "L%=_last_zero:"                  "\n\t"
+     "strb  %[bitmask], [%[reg], #0]" "\n\t"
+     "movs  %[dly], #4"               "\n\t"
+    "L%=_last_delay_T0H:"             "\n\t"
+     "sub   %[dly], #1"               "\n\t"
+     "bne   L%=_last_delay_T0H"       "\n\t"
+     "strb  %[bitmask], [%[reg], #4]" "\n\t"
+     "movs  %[dly], #10"              "\n\t"
+    "L%=_last_delay_T0L:"             "\n\t"
+     "sub   %[dly], #1"               "\n\t"
+     "bne   L%=_last_delay_T0L"       "\n\t"
+     "b     L%=_repeat"               "\n\t"
+    "L%=_last_one:"                   "\n\t"
+     "strb  %[bitmask], [%[reg], #0]" "\n\t"
+     "movs  %[dly], #13"              "\n\t"
+    "L%=_last_delay_T1H:"             "\n\t"
+     "sub   %[dly], #1"               "\n\t"
+     "bne   L%=_last_delay_T1H"       "\n\t"
+     "strb  %[bitmask], [%[reg], #4]" "\n\t"
+     "movs  %[dly], #1"               "\n\t"
+    "L%=_last_delay_T1L:"             "\n\t"
+     "sub   %[dly], #1"               "\n\t"
+     "bne   L%=_last_delay_T1L"       "\n\t"
+     "nop"                            "\n\t"
+    "L%=_repeat:"                     "\n\t"
+     "add   %[p], #1"                 "\n\t"
+     "sub   %[num], #1"               "\n\t"
+     "bne   L%=_begin"                "\n\t"
+    "L%=_done:"                       "\n\t"
+    : [p]       "+r"  (p),
+      [pix]     "=&r" (pix),
+      [count]   "=&r" (count),
+      [dly]     "=&r" (dly),
+      [num]     "+r"  (num)
+    : [bitmask] "r"   (bitmask),
+      [reg]     "r"   (reg)
+  );
+#else
+#error "Sorry, only 48 MHz is supported, please set Tools > CPU Speed to 48 MHz"
+#endif // F_CPU == 48000000
+
+// Begin of support for nRF52 based boards  -------------------------
+
+#elif defined(NRF52) || defined(NRF52_SERIES)
+// [[[Begin of the Neopixel NRF52 EasyDMA implementation
+//                                    by the Hackerspace San Salvador]]]
+// This technique uses the PWM peripheral on the NRF52. The PWM uses the
+// EasyDMA feature included on the chip. This technique loads the duty
+// cycle configuration for each cycle when the PWM is enabled. For this
+// to work we need to store a 16 bit configuration for each bit of the
+// RGB(W) values in the pixel buffer.
+// Comparator values for the PWM were hand picked and are guaranteed to
+// be 100% organic to preserve freshness and high accuracy. Current
+// parameters are:
+//   * PWM Clock: 16Mhz
+//   * Minimum step time: 62.5ns
+//   * Time for zero in high (T0H): 0.31ms
+//   * Time for one in high (T1H): 0.75ms
+//   * Cycle time:  1.25us
+//   * Frequency: 800Khz
+// For 400Khz we just double the calculated times.
+// ---------- BEGIN Constants for the EasyDMA implementation -----------
+// The PWM starts the duty cycle in LOW. To start with HIGH we
+// need to set the 15th bit on each register.
+
+// WS2812 (rev A) timing is 0.35 and 0.7us
+//#define MAGIC_T0H               5UL | (0x8000) // 0.3125us
+//#define MAGIC_T1H              12UL | (0x8000) // 0.75us
+
+// WS2812B (rev B) timing is 0.4 and 0.8 us
+#define MAGIC_T0H               6UL | (0x8000) // 0.375us
+#define MAGIC_T1H              13UL | (0x8000) // 0.8125us
+
+// WS2811 (400 khz) timing is 0.5 and 1.2
+#define MAGIC_T0H_400KHz        8UL  | (0x8000) // 0.5us
+#define MAGIC_T1H_400KHz        19UL | (0x8000) // 1.1875us
+
+// For 400Khz, we double value of CTOPVAL
+#define CTOPVAL                20UL            // 1.25us
+#define CTOPVAL_400KHz         40UL            // 2.5us
+
+// ---------- END Constants for the EasyDMA implementation -------------
+//
+// If there is no device available an alternative cycle-counter
+// implementation is tried.
+// The nRF52 runs with a fixed clock of 64Mhz. The alternative
+// implementation is the same as the one used for the Teensy 3.0/1/2 but
+// with the Nordic SDK HAL & registers syntax.
+// The number of cycles was hand picked and is guaranteed to be 100%
+// organic to preserve freshness and high accuracy.
+// ---------- BEGIN Constants for cycle counter implementation ---------
+#define CYCLES_800_T0H  18  // ~0.36 uS
+#define CYCLES_800_T1H  41  // ~0.76 uS
+#define CYCLES_800      71  // ~1.25 uS
+
+#define CYCLES_400_T0H  26  // ~0.50 uS
+#define CYCLES_400_T1H  70  // ~1.26 uS
+#define CYCLES_400      156 // ~2.50 uS
+// ---------- END of Constants for cycle counter implementation --------
+
+  // To support both the SoftDevice + Neopixels we use the EasyDMA
+  // feature from the NRF25. However this technique implies to
+  // generate a pattern and store it on the memory. The actual
+  // memory used in bytes corresponds to the following formula:
+  //              totalMem = numBytes*8*2+(2*2)
+  // The two additional bytes at the end are needed to reset the
+  // sequence.
+  //
+  // If there is not enough memory, we will fall back to cycle counter
+  // using DWT
+  uint32_t  pattern_size   = numBytes*8*sizeof(uint16_t)+2*sizeof(uint16_t);
+  uint16_t* pixels_pattern = NULL;
+
+  NRF_PWM_Type* pwm = NULL;
+
+  // Try to find a free PWM device, which is not enabled
+  // and has no connected pins
+  NRF_PWM_Type* PWM[] = {
+    NRF_PWM0, NRF_PWM1, NRF_PWM2
+#if defined(NRF_PWM3)
+    ,NRF_PWM3
+#endif
+  };
+
+  for(unsigned int device = 0; device < (sizeof(PWM)/sizeof(PWM[0])); device++) {
+    if( (PWM[device]->ENABLE == 0)                            &&
+        (PWM[device]->PSEL.OUT[0] & PWM_PSEL_OUT_CONNECT_Msk) &&
+        (PWM[device]->PSEL.OUT[1] & PWM_PSEL_OUT_CONNECT_Msk) &&
+        (PWM[device]->PSEL.OUT[2] & PWM_PSEL_OUT_CONNECT_Msk) &&
+        (PWM[device]->PSEL.OUT[3] & PWM_PSEL_OUT_CONNECT_Msk)
+    ) {
+      pwm = PWM[device];
+      break;
+    }
+  }
+
+  // only malloc if there is PWM device available
+  if ( pwm != NULL ) {
+    #if defined(ARDUINO_NRF52_ADAFRUIT) // use thread-safe malloc
+      pixels_pattern = (uint16_t *) rtos_malloc(pattern_size);
+    #else
+      pixels_pattern = (uint16_t *) malloc(pattern_size);
+    #endif
+  }
+
+  // Use the identified device to choose the implementation
+  // If a PWM device is available use DMA
+  if( (pixels_pattern != NULL) && (pwm != NULL) ) {
+    uint16_t pos = 0; // bit position
+
+    for(uint16_t n=0; n<numBytes; n++) {
+      uint8_t pix = pixels[n];
+
+      for(uint8_t mask=0x80; mask>0; mask >>= 1) {
+        #if defined(NEO_KHZ400)
+        if( !is800KHz ) {
+          pixels_pattern[pos] = (pix & mask) ? MAGIC_T1H_400KHz : MAGIC_T0H_400KHz;
+        }else
+        #endif
+        {
+          pixels_pattern[pos] = (pix & mask) ? MAGIC_T1H : MAGIC_T0H;
+        }
+
+        pos++;
+      }
+    }
+
+    // Zero padding to indicate the end of que sequence
+    pixels_pattern[pos++] = 0 | (0x8000); // Seq end
+    pixels_pattern[pos++] = 0 | (0x8000); // Seq end
+
+    // Set the wave mode to count UP
+    pwm->MODE = (PWM_MODE_UPDOWN_Up << PWM_MODE_UPDOWN_Pos);
+
+    // Set the PWM to use the 16MHz clock
+    pwm->PRESCALER = (PWM_PRESCALER_PRESCALER_DIV_1 << PWM_PRESCALER_PRESCALER_Pos);
+
+    // Setting of the maximum count
+    // but keeping it on 16Mhz allows for more granularity just
+    // in case someone wants to do more fine-tuning of the timing.
+#if defined(NEO_KHZ400)
+    if( !is800KHz ) {
+      pwm->COUNTERTOP = (CTOPVAL_400KHz << PWM_COUNTERTOP_COUNTERTOP_Pos);
+    }else
+#endif
+    {
+      pwm->COUNTERTOP = (CTOPVAL << PWM_COUNTERTOP_COUNTERTOP_Pos);
+    }
+
+    // Disable loops, we want the sequence to repeat only once
+    pwm->LOOP = (PWM_LOOP_CNT_Disabled << PWM_LOOP_CNT_Pos);
+
+    // On the "Common" setting the PWM uses the same pattern for the
+    // for supported sequences. The pattern is stored on half-word
+    // of 16bits
+    pwm->DECODER = (PWM_DECODER_LOAD_Common << PWM_DECODER_LOAD_Pos) |
+                   (PWM_DECODER_MODE_RefreshCount << PWM_DECODER_MODE_Pos);
+
+    // Pointer to the memory storing the patter
+    pwm->SEQ[0].PTR = (uint32_t)(pixels_pattern) << PWM_SEQ_PTR_PTR_Pos;
+
+    // Calculation of the number of steps loaded from memory.
+    pwm->SEQ[0].CNT = (pattern_size/sizeof(uint16_t)) << PWM_SEQ_CNT_CNT_Pos;
+
+    // The following settings are ignored with the current config.
+    pwm->SEQ[0].REFRESH  = 0;
+    pwm->SEQ[0].ENDDELAY = 0;
+
+    // The Neopixel implementation is a blocking algorithm. DMA
+    // allows for non-blocking operation. To "simulate" a blocking
+    // operation we enable the interruption for the end of sequence
+    // and block the execution thread until the event flag is set by
+    // the peripheral.
+//    pwm->INTEN |= (PWM_INTEN_SEQEND0_Enabled<<PWM_INTEN_SEQEND0_Pos);
+
+    // PSEL must be configured before enabling PWM
+    #if defined(ARDUINO_ARCH_NRF52840)
+    pwm->PSEL.OUT[0] = g_APinDescription[pin].name;
+    #else
+    pwm->PSEL.OUT[0] = g_ADigitalPinMap[pin];
+    #endif
+
+    // Enable the PWM
+    pwm->ENABLE = 1;
+
+    // After all of this and many hours of reading the documentation
+    // we are ready to start the sequence...
+    pwm->EVENTS_SEQEND[0]  = 0;
+    pwm->TASKS_SEQSTART[0] = 1;
+
+    // But we have to wait for the flag to be set.
+    while(!pwm->EVENTS_SEQEND[0])
+    {
+      #if defined(ARDUINO_NRF52_ADAFRUIT) || defined(ARDUINO_ARCH_NRF52840)
+      yield();
+      #endif
+    }
+
+    // Before leave we clear the flag for the event.
+    pwm->EVENTS_SEQEND[0] = 0;
+
+    // We need to disable the device and disconnect
+    // all the outputs before leave or the device will not
+    // be selected on the next call.
+    // TODO: Check if disabling the device causes performance issues.
+    pwm->ENABLE = 0;
+
+    pwm->PSEL.OUT[0] = 0xFFFFFFFFUL;
+
+    #if defined(ARDUINO_NRF52_ADAFRUIT)  // use thread-safe free
+      rtos_free(pixels_pattern);
+    #else
+      free(pixels_pattern);
+    #endif
+  }// End of DMA implementation
+  // ---------------------------------------------------------------------
+  else{
+#ifndef ARDUINO_ARCH_NRF52840     
+    // Fall back to DWT
+    #if defined(ARDUINO_NRF52_ADAFRUIT)
+      // Bluefruit Feather 52 uses freeRTOS
+      // Critical Section is used since it does not block SoftDevice execution
+      taskENTER_CRITICAL();
+    #elif defined(NRF52_DISABLE_INT)
+      // If you are using the Bluetooth SoftDevice we advise you to not disable
+      // the interrupts. Disabling the interrupts even for short periods of time
+      // causes the SoftDevice to stop working.
+      // Disable the interrupts only in cases where you need high performance for
+      // the LEDs and if you are not using the EasyDMA feature.
+      __disable_irq();
+    #endif
+
+    NRF_GPIO_Type* nrf_port = (NRF_GPIO_Type*) digitalPinToPort(pin);
+    uint32_t pinMask = digitalPinToBitMask(pin);
+
+    uint32_t CYCLES_X00     = CYCLES_800;
+    uint32_t CYCLES_X00_T1H = CYCLES_800_T1H;
+    uint32_t CYCLES_X00_T0H = CYCLES_800_T0H;
+
+#if defined(NEO_KHZ400)
+    if( !is800KHz )
+    {
+      CYCLES_X00     = CYCLES_400;
+      CYCLES_X00_T1H = CYCLES_400_T1H;
+      CYCLES_X00_T0H = CYCLES_400_T0H;
+    }
+#endif
+
+    // Enable DWT in debug core
+    CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
+    DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
+
+    // Tries to re-send the frame if is interrupted by the SoftDevice.
+    while(1) {
+      uint8_t *p = pixels;
+
+      uint32_t cycStart = DWT->CYCCNT;
+      uint32_t cyc = 0;
+
+      for(uint16_t n=0; n<numBytes; n++) {
+        uint8_t pix = *p++;
+
+        for(uint8_t mask = 0x80; mask; mask >>= 1) {
+          while(DWT->CYCCNT - cyc < CYCLES_X00);
+          cyc  = DWT->CYCCNT;
+
+          nrf_port->OUTSET |= pinMask;
+
+          if(pix & mask) {
+            while(DWT->CYCCNT - cyc < CYCLES_X00_T1H);
+          } else {
+            while(DWT->CYCCNT - cyc < CYCLES_X00_T0H);
+          }
+
+          nrf_port->OUTCLR |= pinMask;
+        }
+      }
+      while(DWT->CYCCNT - cyc < CYCLES_X00);
+
+
+      // If total time longer than 25%, resend the whole data.
+      // Since we are likely to be interrupted by SoftDevice
+      if ( (DWT->CYCCNT - cycStart) < ( 8*numBytes*((CYCLES_X00*5)/4) ) ) {
+        break;
+      }
+
+      // re-send need 300us delay
+      delayMicroseconds(300);
+    }
+
+    // Enable interrupts again
+    #if defined(ARDUINO_NRF52_ADAFRUIT)
+      taskEXIT_CRITICAL();
+    #elif defined(NRF52_DISABLE_INT)
+      __enable_irq();
+    #endif
+#endif
+  }
+// END of NRF52 implementation
+
+#elif defined (__SAMD21E17A__) || defined(__SAMD21G18A__)  || defined(__SAMD21E18A__) || defined(__SAMD21J18A__) // Arduino Zero, Gemma/Trinket M0, SODAQ Autonomo and others
+  // Tried this with a timer/counter, couldn't quite get adequate
+  // resolution. So yay, you get a load of goofball NOPs...
+
+  uint8_t  *ptr, *end, p, bitMask, portNum;
+  uint32_t  pinMask;
+
+  portNum =  g_APinDescription[pin].ulPort;
+  pinMask =  1ul << g_APinDescription[pin].ulPin;
+  ptr     =  pixels;
+  end     =  ptr + numBytes;
+  p       = *ptr++;
+  bitMask =  0x80;
+
+  volatile uint32_t *set = &(PORT->Group[portNum].OUTSET.reg),
+                    *clr = &(PORT->Group[portNum].OUTCLR.reg);
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+    for(;;) {
+      *set = pinMask;
+      asm("nop; nop; nop; nop; nop; nop; nop; nop;");
+      if(p & bitMask) {
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop;");
+        *clr = pinMask;
+      } else {
+        *clr = pinMask;
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop;");
+      }
+      if(bitMask >>= 1) {
+        asm("nop; nop; nop; nop; nop; nop; nop; nop; nop;");
+      } else {
+        if(ptr >= end) break;
+        p       = *ptr++;
+        bitMask = 0x80;
+      }
+    }
+#if defined(NEO_KHZ400)
+  } else { // 400 KHz bitstream
+    for(;;) {
+      *set = pinMask;
+      asm("nop; nop; nop; nop; nop; nop; nop; nop; nop; nop; nop;");
+      if(p & bitMask) {
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop;");
+        *clr = pinMask;
+      } else {
+        *clr = pinMask;
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop;");
+      }
+      asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+          "nop; nop; nop; nop; nop; nop; nop; nop;"
+          "nop; nop; nop; nop; nop; nop; nop; nop;"
+          "nop; nop; nop; nop; nop; nop; nop; nop;");
+      if(bitMask >>= 1) {
+        asm("nop; nop; nop; nop; nop; nop; nop;");
+      } else {
+        if(ptr >= end) break;
+        p       = *ptr++;
+        bitMask = 0x80;
+      }
+    }
+  }
+#endif
+
+#elif defined (__SAMD51__) // M4
+
+  uint8_t  *ptr, *end, p, bitMask, portNum, bit;
+  uint32_t  pinMask;
+
+  portNum =  g_APinDescription[pin].ulPort;
+  pinMask =  1ul << g_APinDescription[pin].ulPin;
+  ptr     =  pixels;
+  end     =  ptr + numBytes;
+  p       = *ptr++;
+  bitMask =  0x80;
+
+  volatile uint32_t *set = &(PORT->Group[portNum].OUTSET.reg),
+                    *clr = &(PORT->Group[portNum].OUTCLR.reg);
+
+  // SAMD51 overclock-compatible timing is only a mild abomination.
+  // It uses SysTick for a consistent clock reference regardless of
+  // optimization / cache settings.  That's the good news.  The bad news,
+  // since SysTick->VAL is a volatile type it's slow to access...and then,
+  // with the SysTick interval that Arduino sets up (1 ms), this would
+  // require a subtract and MOD operation for gauging elapsed time, and
+  // all taken in combination that lacks adequate temporal resolution
+  // for NeoPixel timing.  So a kind of horrible thing is done here...
+  // since interrupts are turned off anyway and it's generally accepted
+  // by now that we're gonna lose track of time in the NeoPixel lib,
+  // the SysTick timer is reconfigured for a period matching the NeoPixel
+  // bit timing (either 800 or 400 KHz) and we watch SysTick->VAL very
+  // closely (just a threshold, no subtract or MOD or anything) and that
+  // seems to work just well enough.  When finished, the SysTick
+  // peripheral is set back to its original state.
+
+  uint32_t t0, t1, top, ticks,
+           saveLoad = SysTick->LOAD, saveVal = SysTick->VAL;
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+    top =       (uint32_t)(F_CPU * 0.00000125); // Bit hi + lo = 1.25 uS
+    t0  = top - (uint32_t)(F_CPU * 0.00000040); // 0 = 0.4 uS hi
+    t1  = top - (uint32_t)(F_CPU * 0.00000080); // 1 = 0.8 uS hi
+#if defined(NEO_KHZ400)
+  } else { // 400 KHz bitstream
+    top =       (uint32_t)(F_CPU * 0.00000250); // Bit hi + lo = 2.5 uS
+    t0  = top - (uint32_t)(F_CPU * 0.00000050); // 0 = 0.5 uS hi
+    t1  = top - (uint32_t)(F_CPU * 0.00000120); // 1 = 1.2 uS hi
+  }
+#endif
+
+  SysTick->LOAD = top;               // Config SysTick for NeoPixel bit freq
+  SysTick->VAL  = top;               // Set to start value (counts down)
+  (void)SysTick->VAL;                // Dummy read helps sync up 1st bit
+
+  for(;;) {
+    *set  = pinMask;                 // Set output high
+    ticks = (p & bitMask) ? t1 : t0; // SysTick threshold,
+    while(SysTick->VAL > ticks);     // wait for it
+    *clr  = pinMask;                 // Set output low
+    if(!(bitMask >>= 1)) {           // Next bit for this byte...done?
+      if(ptr >= end) break;          // If last byte sent, exit loop
+      p       = *ptr++;              // Fetch next byte
+      bitMask = 0x80;                // Reset bitmask
+    }
+    while(SysTick->VAL <= ticks);    // Wait for rollover to 'top'
+  }
+
+  SysTick->LOAD = saveLoad;          // Restore SysTick rollover to 1 ms
+  SysTick->VAL  = saveVal;           // Restore SysTick value
+
+#elif defined (ARDUINO_STM32_FEATHER) // FEATHER WICED (120MHz)
+
+  // Tried this with a timer/counter, couldn't quite get adequate
+  // resolution. So yay, you get a load of goofball NOPs...
+
+  uint8_t  *ptr, *end, p, bitMask;
+  uint32_t  pinMask;
+
+  pinMask =  BIT(PIN_MAP[pin].gpio_bit);
+  ptr     =  pixels;
+  end     =  ptr + numBytes;
+  p       = *ptr++;
+  bitMask =  0x80;
+
+  volatile uint16_t *set = &(PIN_MAP[pin].gpio_device->regs->BSRRL);
+  volatile uint16_t *clr = &(PIN_MAP[pin].gpio_device->regs->BSRRH);
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+    for(;;) {
+      if(p & bitMask) { // ONE
+        // High 800ns
+        *set = pinMask;
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop;");
+        // Low 450ns
+        *clr = pinMask;
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop;");
+      } else { // ZERO
+        // High 400ns
+        *set = pinMask;
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop;");
+        // Low 850ns
+        *clr = pinMask;
+        asm("nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop; nop; nop; nop; nop;"
+            "nop; nop; nop; nop;");
+      }
+      if(bitMask >>= 1) {
+        // Move on to the next pixel
+        asm("nop;");
+      } else {
+        if(ptr >= end) break;
+        p       = *ptr++;
+        bitMask = 0x80;
+      }
+    }
+#if defined(NEO_KHZ400)
+  } else { // 400 KHz bitstream
+    // ToDo!
+  }
+#endif
+
+#elif defined(TARGET_LPC1768)
+  uint8_t  *ptr, *end, p, bitMask;
+  ptr     =  pixels;
+  end     =  ptr + numBytes;
+  p       = *ptr++;
+  bitMask =  0x80;
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+    for(;;) {
+      if(p & bitMask) {
+        // data ONE high
+        // min: 550 typ: 700 max: 5,500
+        gpio_set(pin);
+        time::delay_ns(550);
+        // min: 450 typ: 600 max: 5,000
+        gpio_clear(pin);
+        time::delay_ns(450);
+      } else {
+        // data ZERO high
+        // min: 200  typ: 350 max: 500
+        gpio_set(pin);
+        time::delay_ns(200);
+        // data low
+        // min: 450 typ: 600 max: 5,000
+        gpio_clear(pin);
+        time::delay_ns(450);
+      }
+      if(bitMask >>= 1) {
+        // Move on to the next pixel
+        asm("nop;");
+      } else {
+        if(ptr >= end) break;
+        p       = *ptr++;
+        bitMask = 0x80;
+      }
+    }
+#if defined(NEO_KHZ400)
+  } else { // 400 KHz bitstream
+    // ToDo!
+  }
+#endif
+#elif defined(ARDUINO_ARCH_STM32) || defined(ARDUINO_ARCH_ARDUINO_CORE_STM32)
+  uint8_t           *p   = pixels, *end = p + numBytes,
+                    pix = *p++, mask = 0x80;
+  uint32_t          cyc;
+  uint32_t saveLoad = SysTick->LOAD, saveVal = SysTick->VAL;
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+    uint32_t top = (F_CPU /  800000);       // 1.25µs
+    uint32_t t0  = top - (F_CPU / 2500000); // 0.4µs
+    uint32_t t1  = top - (F_CPU / 1250000); // 0.8µs
+    SysTick->LOAD = top - 1; // Config SysTick for NeoPixel bit freq
+    SysTick->VAL  = 0; // Set to start value
+    for(;;) {
+      LL_GPIO_SetOutputPin(gpioPort, gpioPin);
+      cyc = (pix & mask) ? t1 : t0;
+      while(SysTick->VAL > cyc);
+      LL_GPIO_ResetOutputPin(gpioPort, gpioPin);
+      if(!(mask >>= 1)) {
+        if(p >= end) break;
+        pix       = *p++;
+        mask = 0x80;
+      }
+      while(SysTick->VAL <= cyc);
+    }
+#if defined(NEO_KHZ400)
+  } else { // 400 kHz bitstream
+    uint32_t top = (F_CPU /  400000);       // 2.5µs
+    uint32_t t0  = top - (F_CPU / 2000000); // 0.5µs
+    uint32_t t1  = top - (F_CPU /  833333); // 1.2µs
+    SysTick->LOAD = top - 1; // Config SysTick for NeoPixel bit freq
+    SysTick->VAL  = 0;       // Set to start value
+    for(;;) {
+      LL_GPIO_SetOutputPin(gpioPort, gpioPin);
+      cyc = (pix & mask) ? t1 : t0;
+      while(SysTick->VAL > cyc);
+      LL_GPIO_ResetOutputPin(gpioPort, gpioPin);
+      if(!(mask >>= 1)) {
+        if(p >= end) break;
+        pix       = *p++;
+        mask = 0x80;
+      }
+      while(SysTick->VAL <= cyc);
+    }
+  }
+#endif // NEO_KHZ400
+  SysTick->LOAD = saveLoad;          // Restore SysTick rollover to 1 ms
+  SysTick->VAL  = saveVal;           // Restore SysTick value
+#elif defined (NRF51)
+  uint8_t          *p   = pixels,
+                    pix, count, mask;
+  int32_t         num = numBytes;
+  unsigned int bitmask = ( 1 << g_ADigitalPinMap[pin] );
+// https://github.com/sandeepmistry/arduino-nRF5/blob/dc53980c8bac27898fca90d8ecb268e11111edc1/variants/BBCmicrobit/variant.cpp
+
+  volatile unsigned int *reg = (unsigned int *) (0x50000000UL + 0x508);
+
+// https://github.com/sandeepmistry/arduino-nRF5/blob/dc53980c8bac27898fca90d8ecb268e11111edc1/cores/nRF5/SDK/components/device/nrf51.h
+// http://www.iot-programmer.com/index.php/books/27-micro-bit-iot-in-c/chapters-micro-bit-iot-in-c/47-micro-bit-iot-in-c-fast-memory-mapped-gpio?showall=1
+// https://github.com/Microsoft/pxt-neopixel/blob/master/sendbuffer.asm
+
+  asm volatile(
+    // "cpsid i" ; disable irq
+
+    //    b .start
+    "b  L%=_start"                    "\n\t"
+    // .nextbit:               ;            C0
+    "L%=_nextbit:"                    "\n\t"          //;            C0
+    //    str r1, [r3, #0]    ; pin := hi  C2
+    "strb %[bitmask], [%[reg], #0]"   "\n\t"          //; pin := hi  C2
+    //    tst r6, r0          ;            C3
+    "tst %[mask], %[pix]"             "\n\t"//          ;            C3
+    //    bne .islate         ;            C4
+    "bne L%=_islate"                  "\n\t"          //;            C4
+    //    str r1, [r2, #0]    ; pin := lo  C6
+    "strb %[bitmask], [%[reg], #4]"   "\n\t"          //; pin := lo  C6
+    // .islate:
+    "L%=_islate:"                     "\n\t"
+    //    lsrs r6, r6, #1     ; r6 >>= 1   C7
+    "lsr %[mask], %[mask], #1"       "\n\t"          //; r6 >>= 1   C7
+    //    bne .justbit        ;            C8
+    "bne L%=_justbit"                 "\n\t"          //;            C8
+
+    //    ; not just a bit - need new byte
+    //    adds r4, #1         ; r4++       C9
+    "add %[p], #1"                   "\n\t"          //; r4++       C9
+    //    subs r5, #1         ; r5--       C10
+    "sub %[num], #1"                 "\n\t"          //; r5--       C10
+    //    bcc .stop           ; if (r5<0) goto .stop  C11
+    "bcc L%=_stop"                    "\n\t"          //; if (r5<0) goto .stop  C11
+    // .start:
+    "L%=_start:"
+    //    movs r6, #0x80      ; reset mask C12
+    "movs %[mask], #0x80"             "\n\t"          //; reset mask C12
+    //    nop                 ;            C13
+    "nop"                             "\n\t"          //;            C13
+
+    // .common:               ;             C13
+    "L%=_common:"                     "\n\t"          //;            C13
+    //    str r1, [r2, #0]   ; pin := lo   C15
+    "strb %[bitmask], [%[reg], #4]"   "\n\t"          //; pin := lo  C15
+    //    ; always re-load byte - it just fits with the cycles better this way
+    //    ldrb r0, [r4, #0]  ; r0 := *r4   C17
+    "ldrb  %[pix], [%[p], #0]"        "\n\t"          //; r0 := *r4   C17
+    //    b .nextbit         ;             C20
+    "b L%=_nextbit"                   "\n\t"          //;             C20
+
+    // .justbit: ; C10
+    "L%=_justbit:"                    "\n\t"          //; C10
+    //    ; no nops, branch taken is already 3 cycles
+    //    b .common ; C13
+    "b L%=_common"                    "\n\t"          //; C13
+
+    // .stop:
+    "L%=_stop:"                       "\n\t"
+    //    str r1, [r2, #0]   ; pin := lo
+    "strb %[bitmask], [%[reg], #4]"   "\n\t"          //; pin := lo
+    //    cpsie i            ; enable irq
+
+    : [p] "+r" (p),
+    [pix] "=&r" (pix),
+    [count] "=&r" (count),
+    [mask] "=&r" (mask),
+    [num] "+r" (num)
+    : [bitmask] "r" (bitmask),
+    [reg] "r" (reg)
+  );
+
+#elif defined(__SAM3X8E__) // Arduino Due
+
+  #define SCALE      VARIANT_MCK / 2UL / 1000000UL
+  #define INST       (2UL * F_CPU / VARIANT_MCK)
+  #define TIME_800_0 ((int)(0.40 * SCALE + 0.5) - (5 * INST))
+  #define TIME_800_1 ((int)(0.80 * SCALE + 0.5) - (5 * INST))
+  #define PERIOD_800 ((int)(1.25 * SCALE + 0.5) - (5 * INST))
+  #define TIME_400_0 ((int)(0.50 * SCALE + 0.5) - (5 * INST))
+  #define TIME_400_1 ((int)(1.20 * SCALE + 0.5) - (5 * INST))
+  #define PERIOD_400 ((int)(2.50 * SCALE + 0.5) - (5 * INST))
+
+  int             pinMask, time0, time1, period, t;
+  Pio            *port;
+  volatile WoReg *portSet, *portClear, *timeValue, *timeReset;
+  uint8_t        *p, *end, pix, mask;
+
+  pmc_set_writeprotect(false);
+  pmc_enable_periph_clk((uint32_t)TC3_IRQn);
+  TC_Configure(TC1, 0,
+    TC_CMR_WAVE | TC_CMR_WAVSEL_UP | TC_CMR_TCCLKS_TIMER_CLOCK1);
+  TC_Start(TC1, 0);
+
+  pinMask   = g_APinDescription[pin].ulPin; // Don't 'optimize' these into
+  port      = g_APinDescription[pin].pPort; // declarations above. Want to
+  portSet   = &(port->PIO_SODR);            // burn a few cycles after
+  portClear = &(port->PIO_CODR);            // starting timer to minimize
+  timeValue = &(TC1->TC_CHANNEL[0].TC_CV);  // the initial 'while'.
+  timeReset = &(TC1->TC_CHANNEL[0].TC_CCR);
+  p         =  pixels;
+  end       =  p + numBytes;
+  pix       = *p++;
+  mask      = 0x80;
+
+#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
+  if(is800KHz) {
+#endif
+    time0  = TIME_800_0;
+    time1  = TIME_800_1;
+    period = PERIOD_800;
+#if defined(NEO_KHZ400)
+  } else { // 400 KHz bitstream
+    time0  = TIME_400_0;
+    time1  = TIME_400_1;
+    period = PERIOD_400;
+  }
+#endif
+
+  for(t = time0;; t = time0) {
+    if(pix & mask) t = time1;
+    while(*timeValue < (unsigned)period);
+    *portSet   = pinMask;
+    *timeReset = TC_CCR_CLKEN | TC_CCR_SWTRG;
+    while(*timeValue < (unsigned)t);
+    *portClear = pinMask;
+    if(!(mask >>= 1)) {   // This 'inside-out' loop logic utilizes
+      if(p >= end) break; // idle time to minimize inter-byte delays.
+      pix = *p++;
+      mask = 0x80;
+    }
+  }
+  while(*timeValue < (unsigned)period); // Wait for last bit
+  TC_Stop(TC1, 0);
+
+#endif // end Due
+
+// END ARM ----------------------------------------------------------------
+
+
+#elif defined(ESP8266) || defined(ESP32)
+
+// ESP8266 ----------------------------------------------------------------
+
+  // ESP8266 show() is external to enforce ICACHE_RAM_ATTR execution
+  espShow(pin, pixels, numBytes, is800KHz);
+
+#elif defined(KENDRYTE_K210)
+
+  k210Show(pin, pixels, numBytes, is800KHz);
+  
+#elif defined(__ARDUINO_ARC__)
+
+// Arduino 101  -----------------------------------------------------------
+
+#define NOPx7 { __builtin_arc_nop(); \
+  __builtin_arc_nop(); __builtin_arc_nop(); \
+  __builtin_arc_nop(); __builtin_arc_nop(); \
+  __builtin_arc_nop(); __builtin_arc_nop(); }
+
+  PinDescription *pindesc = &g_APinDescription[pin];
+  register uint32_t loop = 8 * numBytes; // one loop to handle all bytes and all bits
+  register uint8_t *p = pixels;
+  register uint32_t currByte = (uint32_t) (*p);
+  register uint32_t currBit = 0x80 & currByte;
+  register uint32_t bitCounter = 0;
+  register uint32_t first = 1;
+
+  // The loop is unusual. Very first iteration puts all the way LOW to the wire -
+  // constant LOW does not affect NEOPIXEL, so there is no visible effect displayed.
+  // During that very first iteration CPU caches instructions in the loop.
+  // Because of the caching process, "CPU slows down". NEOPIXEL pulse is very time sensitive
+  // that's why we let the CPU cache first and we start regular pulse from 2nd iteration
+  if (pindesc->ulGPIOType == SS_GPIO) {
+    register uint32_t reg = pindesc->ulGPIOBase + SS_GPIO_SWPORTA_DR;
+    uint32_t reg_val = __builtin_arc_lr((volatile uint32_t)reg);
+    register uint32_t reg_bit_high = reg_val | (1 << pindesc->ulGPIOId);
+    register uint32_t reg_bit_low  = reg_val & ~(1 << pindesc->ulGPIOId);
+
+    loop += 1; // include first, special iteration
+    while(loop--) {
+      if(!first) {
+        currByte <<= 1;
+        bitCounter++;
+      }
+
+      // 1 is >550ns high and >450ns low; 0 is 200..500ns high and >450ns low
+      __builtin_arc_sr(first ? reg_bit_low : reg_bit_high, (volatile uint32_t)reg);
+      if(currBit) { // ~400ns HIGH (740ns overall)
+        NOPx7
+        NOPx7
+      }
+      // ~340ns HIGH
+      NOPx7
+     __builtin_arc_nop();
+
+      // 820ns LOW; per spec, max allowed low here is 5000ns */
+      __builtin_arc_sr(reg_bit_low, (volatile uint32_t)reg);
+      NOPx7
+      NOPx7
+
+      if(bitCounter >= 8) {
+        bitCounter = 0;
+        currByte = (uint32_t) (*++p);
+      }
+
+      currBit = 0x80 & currByte;
+      first = 0;
+    }
+  } else if(pindesc->ulGPIOType == SOC_GPIO) {
+    register uint32_t reg = pindesc->ulGPIOBase + SOC_GPIO_SWPORTA_DR;
+    uint32_t reg_val = MMIO_REG_VAL(reg);
+    register uint32_t reg_bit_high = reg_val | (1 << pindesc->ulGPIOId);
+    register uint32_t reg_bit_low  = reg_val & ~(1 << pindesc->ulGPIOId);
+
+    loop += 1; // include first, special iteration
+    while(loop--) {
+      if(!first) {
+        currByte <<= 1;
+        bitCounter++;
+      }
+      MMIO_REG_VAL(reg) = first ? reg_bit_low : reg_bit_high;
+      if(currBit) { // ~430ns HIGH (740ns overall)
+        NOPx7
+        NOPx7
+        __builtin_arc_nop();
+      }
+      // ~310ns HIGH
+      NOPx7
+
+      // 850ns LOW; per spec, max allowed low here is 5000ns */
+      MMIO_REG_VAL(reg) = reg_bit_low;
+      NOPx7
+      NOPx7
+
+      if(bitCounter >= 8) {
+        bitCounter = 0;
+        currByte = (uint32_t) (*++p);
+      }
+
+      currBit = 0x80 & currByte;
+      first = 0;
+    }
+  }
+
+#else
+#error Architecture not supported
+#endif
+
+
+// END ARCHITECTURE SELECT ------------------------------------------------
+
+#if !( defined(NRF52) || defined(NRF52_SERIES) )
+  interrupts();
+#endif
+
+  endTime = micros(); // Save EOD time for latch on next call
+}
+
+/*!
+  @brief   Set/change the NeoPixel output pin number. Previous pin,
+           if any, is set to INPUT and the new pin is set to OUTPUT.
+  @param   p  Arduino pin number (-1 = no pin).
+*/
+void Adafruit_NeoPixel::setPin(uint16_t p) {
+  if(begun && (pin >= 0)) pinMode(pin, INPUT);
+  pin = p;
+  if(begun) {
+    pinMode(p, OUTPUT);
+    digitalWrite(p, LOW);
+  }
+#if defined(__AVR__)
+  port    = portOutputRegister(digitalPinToPort(p));
+  pinMask = digitalPinToBitMask(p);
+#endif
+#if defined(ARDUINO_ARCH_STM32) || defined(ARDUINO_ARCH_ARDUINO_CORE_STM32)
+  gpioPort = digitalPinToPort(p);
+  gpioPin = STM_LL_GPIO_PIN(digitalPinToPinName(p));
+#endif
+}
+
+/*!
+  @brief   Set a pixel's color using separate red, green and blue
+           components. If using RGBW pixels, white will be set to 0.
+  @param   n  Pixel index, starting from 0.
+  @param   r  Red brightness, 0 = minimum (off), 255 = maximum.
+  @param   g  Green brightness, 0 = minimum (off), 255 = maximum.
+  @param   b  Blue brightness, 0 = minimum (off), 255 = maximum.
+*/
+void Adafruit_NeoPixel::setPixelColor(
+ uint16_t n, uint8_t r, uint8_t g, uint8_t b) {
+
+  if(n < numLEDs) {
+    if(brightness) { // See notes in setBrightness()
+      r = (r * brightness) >> 8;
+      g = (g * brightness) >> 8;
+      b = (b * brightness) >> 8;
+    }
+    uint8_t *p;
+    if(wOffset == rOffset) { // Is an RGB-type strip
+      p = &pixels[n * 3];    // 3 bytes per pixel
+    } else {                 // Is a WRGB-type strip
+      p = &pixels[n * 4];    // 4 bytes per pixel
+      p[wOffset] = 0;        // But only R,G,B passed -- set W to 0
+    }
+    p[rOffset] = r;          // R,G,B always stored
+    p[gOffset] = g;
+    p[bOffset] = b;
+  }
+}
+
+/*!
+  @brief   Set a pixel's color using separate red, green, blue and white
+           components (for RGBW NeoPixels only).
+  @param   n  Pixel index, starting from 0.
+  @param   r  Red brightness, 0 = minimum (off), 255 = maximum.
+  @param   g  Green brightness, 0 = minimum (off), 255 = maximum.
+  @param   b  Blue brightness, 0 = minimum (off), 255 = maximum.
+  @param   w  White brightness, 0 = minimum (off), 255 = maximum, ignored
+              if using RGB pixels.
+*/
+void Adafruit_NeoPixel::setPixelColor(
+ uint16_t n, uint8_t r, uint8_t g, uint8_t b, uint8_t w) {
+
+  if(n < numLEDs) {
+    if(brightness) { // See notes in setBrightness()
+      r = (r * brightness) >> 8;
+      g = (g * brightness) >> 8;
+      b = (b * brightness) >> 8;
+      w = (w * brightness) >> 8;
+    }
+    uint8_t *p;
+    if(wOffset == rOffset) { // Is an RGB-type strip
+      p = &pixels[n * 3];    // 3 bytes per pixel (ignore W)
+    } else {                 // Is a WRGB-type strip
+      p = &pixels[n * 4];    // 4 bytes per pixel
+      p[wOffset] = w;        // Store W
+    }
+    p[rOffset] = r;          // Store R,G,B
+    p[gOffset] = g;
+    p[bOffset] = b;
+  }
+}
+
+/*!
+  @brief   Set a pixel's color using a 32-bit 'packed' RGB or RGBW value.
+  @param   n  Pixel index, starting from 0.
+  @param   c  32-bit color value. Most significant byte is white (for RGBW
+              pixels) or ignored (for RGB pixels), next is red, then green,
+              and least significant byte is blue.
+*/
+void Adafruit_NeoPixel::setPixelColor(uint16_t n, uint32_t c) {
+  if(n < numLEDs) {
+    uint8_t *p,
+      r = (uint8_t)(c >> 16),
+      g = (uint8_t)(c >>  8),
+      b = (uint8_t)c;
+    if(brightness) { // See notes in setBrightness()
+      r = (r * brightness) >> 8;
+      g = (g * brightness) >> 8;
+      b = (b * brightness) >> 8;
+    }
+    if(wOffset == rOffset) {
+      p = &pixels[n * 3];
+    } else {
+      p = &pixels[n * 4];
+      uint8_t w = (uint8_t)(c >> 24);
+      p[wOffset] = brightness ? ((w * brightness) >> 8) : w;
+    }
+    p[rOffset] = r;
+    p[gOffset] = g;
+    p[bOffset] = b;
+  }
+}
+
+/*!
+  @brief   Fill all or part of the NeoPixel strip with a color.
+  @param   c      32-bit color value. Most significant byte is white (for
+                  RGBW pixels) or ignored (for RGB pixels), next is red,
+                  then green, and least significant byte is blue. If all
+                  arguments are unspecified, this will be 0 (off).
+  @param   first  Index of first pixel to fill, starting from 0. Must be
+                  in-bounds, no clipping is performed. 0 if unspecified.
+  @param   count  Number of pixels to fill, as a positive value. Passing
+                  0 or leaving unspecified will fill to end of strip.
+*/
+void Adafruit_NeoPixel::fill(uint32_t c, uint16_t first, uint16_t count) {
+  uint16_t i, end;
+
+  if(first >= numLEDs) {
+    return; // If first LED is past end of strip, nothing to do
+  }
+
+  // Calculate the index ONE AFTER the last pixel to fill
+  if(count == 0) {
+    // Fill to end of strip
+    end = numLEDs;
+  } else {
+    // Ensure that the loop won't go past the last pixel
+    end = first + count;
+    if(end > numLEDs) end = numLEDs;
+  }
+
+  for(i = first; i < end; i++) {
+    this->setPixelColor(i, c);
+  }
+}
+
+/*!
+  @brief   Convert hue, saturation and value into a packed 32-bit RGB color
+           that can be passed to setPixelColor() or other RGB-compatible
+           functions.
+  @param   hue  An unsigned 16-bit value, 0 to 65535, representing one full
+                loop of the color wheel, which allows 16-bit hues to "roll
+                over" while still doing the expected thing (and allowing
+                more precision than the wheel() function that was common to
+                prior NeoPixel examples).
+  @param   sat  Saturation, 8-bit value, 0 (min or pure grayscale) to 255
+                (max or pure hue). Default of 255 if unspecified.
+  @param   val  Value (brightness), 8-bit value, 0 (min / black / off) to
+                255 (max or full brightness). Default of 255 if unspecified.
+  @return  Packed 32-bit RGB with the most significant byte set to 0 -- the
+           white element of WRGB pixels is NOT utilized. Result is linearly
+           but not perceptually correct, so you may want to pass the result
+           through the gamma32() function (or your own gamma-correction
+           operation) else colors may appear washed out. This is not done
+           automatically by this function because coders may desire a more
+           refined gamma-correction function than the simplified
+           one-size-fits-all operation of gamma32(). Diffusing the LEDs also
+           really seems to help when using low-saturation colors.
+*/
+uint32_t Adafruit_NeoPixel::ColorHSV(uint16_t hue, uint8_t sat, uint8_t val) {
+
+  uint8_t r, g, b;
+
+  // Remap 0-65535 to 0-1529. Pure red is CENTERED on the 64K rollover;
+  // 0 is not the start of pure red, but the midpoint...a few values above
+  // zero and a few below 65536 all yield pure red (similarly, 32768 is the
+  // midpoint, not start, of pure cyan). The 8-bit RGB hexcone (256 values
+  // each for red, green, blue) really only allows for 1530 distinct hues
+  // (not 1536, more on that below), but the full unsigned 16-bit type was
+  // chosen for hue so that one's code can easily handle a contiguous color
+  // wheel by allowing hue to roll over in either direction.
+  hue = (hue * 1530L + 32768) / 65536;
+  // Because red is centered on the rollover point (the +32768 above,
+  // essentially a fixed-point +0.5), the above actually yields 0 to 1530,
+  // where 0 and 1530 would yield the same thing. Rather than apply a
+  // costly modulo operator, 1530 is handled as a special case below.
+
+  // So you'd think that the color "hexcone" (the thing that ramps from
+  // pure red, to pure yellow, to pure green and so forth back to red,
+  // yielding six slices), and with each color component having 256
+  // possible values (0-255), might have 1536 possible items (6*256),
+  // but in reality there's 1530. This is because the last element in
+  // each 256-element slice is equal to the first element of the next
+  // slice, and keeping those in there this would create small
+  // discontinuities in the color wheel. So the last element of each
+  // slice is dropped...we regard only elements 0-254, with item 255
+  // being picked up as element 0 of the next slice. Like this:
+  // Red to not-quite-pure-yellow is:        255,   0, 0 to 255, 254,   0
+  // Pure yellow to not-quite-pure-green is: 255, 255, 0 to   1, 255,   0
+  // Pure green to not-quite-pure-cyan is:     0, 255, 0 to   0, 255, 254
+  // and so forth. Hence, 1530 distinct hues (0 to 1529), and hence why
+  // the constants below are not the multiples of 256 you might expect.
+
+  // Convert hue to R,G,B (nested ifs faster than divide+mod+switch):
+  if(hue < 510) {         // Red to Green-1
+    b = 0;
+    if(hue < 255) {       //   Red to Yellow-1
+      r = 255;
+      g = hue;            //     g = 0 to 254
+    } else {              //   Yellow to Green-1
+      r = 510 - hue;      //     r = 255 to 1
+      g = 255;
+    }
+  } else if(hue < 1020) { // Green to Blue-1
+    r = 0;
+    if(hue <  765) {      //   Green to Cyan-1
+      g = 255;
+      b = hue - 510;      //     b = 0 to 254
+    } else {              //   Cyan to Blue-1
+      g = 1020 - hue;     //     g = 255 to 1
+      b = 255;
+    }
+  } else if(hue < 1530) { // Blue to Red-1
+    g = 0;
+    if(hue < 1275) {      //   Blue to Magenta-1
+      r = hue - 1020;     //     r = 0 to 254
+      b = 255;
+    } else {              //   Magenta to Red-1
+      r = 255;
+      b = 1530 - hue;     //     b = 255 to 1
+    }
+  } else {                // Last 0.5 Red (quicker than % operator)
+    r = 255;
+    g = b = 0;
+  }
+
+  // Apply saturation and value to R,G,B, pack into 32-bit result:
+  uint32_t v1 =   1 + val; // 1 to 256; allows >>8 instead of /255
+  uint16_t s1 =   1 + sat; // 1 to 256; same reason
+  uint8_t  s2 = 255 - sat; // 255 to 0
+  return ((((((r * s1) >> 8) + s2) * v1) & 0xff00) << 8) |
+          (((((g * s1) >> 8) + s2) * v1) & 0xff00)       |
+         ( ((((b * s1) >> 8) + s2) * v1)           >> 8);
+}
+
+/*!
+  @brief   Query the color of a previously-set pixel.
+  @param   n  Index of pixel to read (0 = first).
+  @return  'Packed' 32-bit RGB or WRGB value. Most significant byte is white
+           (for RGBW pixels) or 0 (for RGB pixels), next is red, then green,
+           and least significant byte is blue.
+  @note    If the strip brightness has been changed from the default value
+           of 255, the color read from a pixel may not exactly match what
+           was previously written with one of the setPixelColor() functions.
+           This gets more pronounced at lower brightness levels.
+*/
+uint32_t Adafruit_NeoPixel::getPixelColor(uint16_t n) const {
+  if(n >= numLEDs) return 0; // Out of bounds, return no color.
+
+  uint8_t *p;
+
+  if(wOffset == rOffset) { // Is RGB-type device
+    p = &pixels[n * 3];
+    if(brightness) {
+      // Stored color was decimated by setBrightness(). Returned value
+      // attempts to scale back to an approximation of the original 24-bit
+      // value used when setting the pixel color, but there will always be
+      // some error -- those bits are simply gone. Issue is most
+      // pronounced at low brightness levels.
+      return (((uint32_t)(p[rOffset] << 8) / brightness) << 16) |
+             (((uint32_t)(p[gOffset] << 8) / brightness) <<  8) |
+             ( (uint32_t)(p[bOffset] << 8) / brightness       );
+    } else {
+      // No brightness adjustment has been made -- return 'raw' color
+      return ((uint32_t)p[rOffset] << 16) |
+             ((uint32_t)p[gOffset] <<  8) |
+              (uint32_t)p[bOffset];
+    }
+  } else {                 // Is RGBW-type device
+    p = &pixels[n * 4];
+    if(brightness) { // Return scaled color
+      return (((uint32_t)(p[wOffset] << 8) / brightness) << 24) |
+             (((uint32_t)(p[rOffset] << 8) / brightness) << 16) |
+             (((uint32_t)(p[gOffset] << 8) / brightness) <<  8) |
+             ( (uint32_t)(p[bOffset] << 8) / brightness       );
+    } else { // Return raw color
+      return ((uint32_t)p[wOffset] << 24) |
+             ((uint32_t)p[rOffset] << 16) |
+             ((uint32_t)p[gOffset] <<  8) |
+              (uint32_t)p[bOffset];
+    }
+  }
+}
+
+
+/*!
+  @brief   Adjust output brightness. Does not immediately affect what's
+           currently displayed on the LEDs. The next call to show() will
+           refresh the LEDs at this level.
+  @param   b  Brightness setting, 0=minimum (off), 255=brightest.
+  @note    This was intended for one-time use in one's setup() function,
+           not as an animation effect in itself. Because of the way this
+           library "pre-multiplies" LED colors in RAM, changing the
+           brightness is often a "lossy" operation -- what you write to
+           pixels isn't necessary the same as what you'll read back.
+           Repeated brightness changes using this function exacerbate the
+           problem. Smart programs therefore treat the strip as a
+           write-only resource, maintaining their own state to render each
+           frame of an animation, not relying on read-modify-write.
+*/
+void Adafruit_NeoPixel::setBrightness(uint8_t b) {
+  // Stored brightness value is different than what's passed.
+  // This simplifies the actual scaling math later, allowing a fast
+  // 8x8-bit multiply and taking the MSB. 'brightness' is a uint8_t,
+  // adding 1 here may (intentionally) roll over...so 0 = max brightness
+  // (color values are interpreted literally; no scaling), 1 = min
+  // brightness (off), 255 = just below max brightness.
+  uint8_t newBrightness = b + 1;
+  if(newBrightness != brightness) { // Compare against prior value
+    // Brightness has changed -- re-scale existing data in RAM,
+    // This process is potentially "lossy," especially when increasing
+    // brightness. The tight timing in the WS2811/WS2812 code means there
+    // aren't enough free cycles to perform this scaling on the fly as data
+    // is issued. So we make a pass through the existing color data in RAM
+    // and scale it (subsequent graphics commands also work at this
+    // brightness level). If there's a significant step up in brightness,
+    // the limited number of steps (quantization) in the old data will be
+    // quite visible in the re-scaled version. For a non-destructive
+    // change, you'll need to re-render the full strip data. C'est la vie.
+    uint8_t  c,
+            *ptr           = pixels,
+             oldBrightness = brightness - 1; // De-wrap old brightness value
+    uint16_t scale;
+    if(oldBrightness == 0) scale = 0; // Avoid /0
+    else if(b == 255) scale = 65535 / oldBrightness;
+    else scale = (((uint16_t)newBrightness << 8) - 1) / oldBrightness;
+    for(uint16_t i=0; i<numBytes; i++) {
+      c      = *ptr;
+      *ptr++ = (c * scale) >> 8;
+    }
+    brightness = newBrightness;
+  }
+}
+
+/*!
+  @brief   Retrieve the last-set brightness value for the strip.
+  @return  Brightness value: 0 = minimum (off), 255 = maximum.
+*/
+uint8_t Adafruit_NeoPixel::getBrightness(void) const {
+  return brightness - 1;
+}
+
+/*!
+  @brief   Fill the whole NeoPixel strip with 0 / black / off.
+*/
+void Adafruit_NeoPixel::clear(void) {
+  memset(pixels, 0, numBytes);
+}
+
+// A 32-bit variant of gamma8() that applies the same function
+// to all components of a packed RGB or WRGB value.
+uint32_t Adafruit_NeoPixel::gamma32(uint32_t x) {
+  uint8_t *y = (uint8_t *)&x;
+  // All four bytes of a 32-bit value are filtered even if RGB (not WRGB),
+  // to avoid a bunch of shifting and masking that would be necessary for
+  // properly handling different endianisms (and each byte is a fairly
+  // trivial operation, so it might not even be wasting cycles vs a check
+  // and branch for the RGB case). In theory this might cause trouble *if*
+  // someone's storing information in the unused most significant byte
+  // of an RGB value, but this seems exceedingly rare and if it's
+  // encountered in reality they can mask values going in or coming out.
+  for(uint8_t i=0; i<4; i++) y[i] = gamma8(y[i]);
+  return x; // Packed 32-bit return
+}

src/lib/Adafruit_NeoPixel/Adafruit_NeoPixel.h

+/*!
+ * @file Adafruit_NeoPixel.h
+ *
+ * This is part of Adafruit's NeoPixel library for the Arduino platform,
+ * allowing a broad range of microcontroller boards (most AVR boards,
+ * many ARM devices, ESP8266 and ESP32, among others) to control Adafruit
+ * NeoPixels, FLORA RGB Smart Pixels and compatible devices -- WS2811,
+ * WS2812, WS2812B, SK6812, etc.
+ *
+ * Adafruit invests time and resources providing this open source code,
+ * please support Adafruit and open-source hardware by purchasing products
+ * from Adafruit!
+ *
+ * Written by Phil "Paint Your Dragon" Burgess for Adafruit Industries,
+ * with contributions by PJRC, Michael Miller and other members of the
+ * open source community.
+ *
+ * This file is part of the Adafruit_NeoPixel library.
+ *
+ * Adafruit_NeoPixel is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Adafruit_NeoPixel is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with NeoPixel.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef ADAFRUIT_NEOPIXEL_H
+#define ADAFRUIT_NEOPIXEL_H
+
+#ifdef ARDUINO
+  #if (ARDUINO >= 100)
+  #include <Arduino.h>
+  #else
+  #include <WProgram.h>
+  #include <pins_arduino.h>
+  #endif
+#endif
+
+#ifdef TARGET_LPC1768
+  #include <Arduino.h>
+#endif
+
+// The order of primary colors in the NeoPixel data stream can vary among
+// device types, manufacturers and even different revisions of the same
+// item.  The third parameter to the Adafruit_NeoPixel constructor encodes
+// the per-pixel byte offsets of the red, green and blue primaries (plus
+// white, if present) in the data stream -- the following #defines provide
+// an easier-to-use named version for each permutation. e.g. NEO_GRB
+// indicates a NeoPixel-compatible device expecting three bytes per pixel,
+// with the first byte transmitted containing the green value, second
+// containing red and third containing blue. The in-memory representation
+// of a chain of NeoPixels is the same as the data-stream order; no
+// re-ordering of bytes is required when issuing data to the chain.
+// Most of these values won't exist in real-world devices, but it's done
+// this way so we're ready for it (also, if using the WS2811 driver IC,
+// one might have their pixels set up in any weird permutation).
+
+// Bits 5,4 of this value are the offset (0-3) from the first byte of a
+// pixel to the location of the red color byte.  Bits 3,2 are the green
+// offset and 1,0 are the blue offset.  If it is an RGBW-type device
+// (supporting a white primary in addition to R,G,B), bits 7,6 are the
+// offset to the white byte...otherwise, bits 7,6 are set to the same value
+// as 5,4 (red) to indicate an RGB (not RGBW) device.
+// i.e. binary representation:
+// 0bWWRRGGBB for RGBW devices
+// 0bRRRRGGBB for RGB
+
+// RGB NeoPixel permutations; white and red offsets are always same
+// Offset:         W        R        G        B
+#define NEO_RGB  ((0<<6) | (0<<4) | (1<<2) | (2)) ///< Transmit as R,G,B
+#define NEO_RBG  ((0<<6) | (0<<4) | (2<<2) | (1)) ///< Transmit as R,B,G
+#define NEO_GRB  ((1<<6) | (1<<4) | (0<<2) | (2)) ///< Transmit as G,R,B
+#define NEO_GBR  ((2<<6) | (2<<4) | (0<<2) | (1)) ///< Transmit as G,B,R
+#define NEO_BRG  ((1<<6) | (1<<4) | (2<<2) | (0)) ///< Transmit as B,R,G
+#define NEO_BGR  ((2<<6) | (2<<4) | (1<<2) | (0)) ///< Transmit as B,G,R
+
+// RGBW NeoPixel permutations; all 4 offsets are distinct
+// Offset:         W          R          G          B
+#define NEO_WRGB ((0<<6) | (1<<4) | (2<<2) | (3)) ///< Transmit as W,R,G,B
+#define NEO_WRBG ((0<<6) | (1<<4) | (3<<2) | (2)) ///< Transmit as W,R,B,G
+#define NEO_WGRB ((0<<6) | (2<<4) | (1<<2) | (3)) ///< Transmit as W,G,R,B
+#define NEO_WGBR ((0<<6) | (3<<4) | (1<<2) | (2)) ///< Transmit as W,G,B,R
+#define NEO_WBRG ((0<<6) | (2<<4) | (3<<2) | (1)) ///< Transmit as W,B,R,G
+#define NEO_WBGR ((0<<6) | (3<<4) | (2<<2) | (1)) ///< Transmit as W,B,G,R
+
+#define NEO_RWGB ((1<<6) | (0<<4) | (2<<2) | (3)) ///< Transmit as R,W,G,B
+#define NEO_RWBG ((1<<6) | (0<<4) | (3<<2) | (2)) ///< Transmit as R,W,B,G
+#define NEO_RGWB ((2<<6) | (0<<4) | (1<<2) | (3)) ///< Transmit as R,G,W,B
+#define NEO_RGBW ((3<<6) | (0<<4) | (1<<2) | (2)) ///< Transmit as R,G,B,W
+#define NEO_RBWG ((2<<6) | (0<<4) | (3<<2) | (1)) ///< Transmit as R,B,W,G
+#define NEO_RBGW ((3<<6) | (0<<4) | (2<<2) | (1)) ///< Transmit as R,B,G,W
+
+#define NEO_GWRB ((1<<6) | (2<<4) | (0<<2) | (3)) ///< Transmit as G,W,R,B
+#define NEO_GWBR ((1<<6) | (3<<4) | (0<<2) | (2)) ///< Transmit as G,W,B,R
+#define NEO_GRWB ((2<<6) | (1<<4) | (0<<2) | (3)) ///< Transmit as G,R,W,B
+#define NEO_GRBW ((3<<6) | (1<<4) | (0<<2) | (2)) ///< Transmit as G,R,B,W
+#define NEO_GBWR ((2<<6) | (3<<4) | (0<<2) | (1)) ///< Transmit as G,B,W,R
+#define NEO_GBRW ((3<<6) | (2<<4) | (0<<2) | (1)) ///< Transmit as G,B,R,W
+
+#define NEO_BWRG ((1<<6) | (2<<4) | (3<<2) | (0)) ///< Transmit as B,W,R,G
+#define NEO_BWGR ((1<<6) | (3<<4) | (2<<2) | (0)) ///< Transmit as B,W,G,R
+#define NEO_BRWG ((2<<6) | (1<<4) | (3<<2) | (0)) ///< Transmit as B,R,W,G
+#define NEO_BRGW ((3<<6) | (1<<4) | (2<<2) | (0)) ///< Transmit as B,R,G,W
+#define NEO_BGWR ((2<<6) | (3<<4) | (1<<2) | (0)) ///< Transmit as B,G,W,R
+#define NEO_BGRW ((3<<6) | (2<<4) | (1<<2) | (0)) ///< Transmit as B,G,R,W
+
+// Add NEO_KHZ400 to the color order value to indicate a 400 KHz device.
+// All but the earliest v1 NeoPixels expect an 800 KHz data stream, this is
+// the default if unspecified. Because flash space is very limited on ATtiny
+// devices (e.g. Trinket, Gemma), v1 NeoPixels aren't handled by default on
+// those chips, though it can be enabled by removing the ifndef/endif below,
+// but code will be bigger. Conversely, can disable the NEO_KHZ400 line on
+// other MCUs to remove v1 support and save a little space.
+
+#define NEO_KHZ800 0x0000 ///< 800 KHz data transmission
+#ifndef __AVR_ATtiny85__
+#define NEO_KHZ400 0x0100 ///< 400 KHz data transmission
+#endif
+
+// If 400 KHz support is enabled, the third parameter to the constructor
+// requires a 16-bit value (in order to select 400 vs 800 KHz speed).
+// If only 800 KHz is enabled (as is default on ATtiny), an 8-bit value
+// is sufficient to encode pixel color order, saving some space.
+
+#ifdef NEO_KHZ400
+typedef uint16_t neoPixelType; ///< 3rd arg to Adafruit_NeoPixel constructor
+#else
+typedef uint8_t  neoPixelType; ///< 3rd arg to Adafruit_NeoPixel constructor
+#endif
+
+// These two tables are declared outside the Adafruit_NeoPixel class
+// because some boards may require oldschool compilers that don't
+// handle the C++11 constexpr keyword.
+
+/* A PROGMEM (flash mem) table containing 8-bit unsigned sine wave (0-255).
+   Copy & paste this snippet into a Python REPL to regenerate:
+import math
+for x in range(256):
+    print("{:3},".format(int((math.sin(x/128.0*math.pi)+1.0)*127.5+0.5))),
+    if x&15 == 15: print
+*/
+static const uint8_t PROGMEM _NeoPixelSineTable[256] = {
+  128,131,134,137,140,143,146,149,152,155,158,162,165,167,170,173,
+  176,179,182,185,188,190,193,196,198,201,203,206,208,211,213,215,
+  218,220,222,224,226,228,230,232,234,235,237,238,240,241,243,244,
+  245,246,248,249,250,250,251,252,253,253,254,254,254,255,255,255,
+  255,255,255,255,254,254,254,253,253,252,251,250,250,249,248,246,
+  245,244,243,241,240,238,237,235,234,232,230,228,226,224,222,220,
+  218,215,213,211,208,206,203,201,198,196,193,190,188,185,182,179,
+  176,173,170,167,165,162,158,155,152,149,146,143,140,137,134,131,
+  128,124,121,118,115,112,109,106,103,100, 97, 93, 90, 88, 85, 82,
+   79, 76, 73, 70, 67, 65, 62, 59, 57, 54, 52, 49, 47, 44, 42, 40,
+   37, 35, 33, 31, 29, 27, 25, 23, 21, 20, 18, 17, 15, 14, 12, 11,
+   10,  9,  7,  6,  5,  5,  4,  3,  2,  2,  1,  1,  1,  0,  0,  0,
+    0,  0,  0,  0,  1,  1,  1,  2,  2,  3,  4,  5,  5,  6,  7,  9,
+   10, 11, 12, 14, 15, 17, 18, 20, 21, 23, 25, 27, 29, 31, 33, 35,
+   37, 40, 42, 44, 47, 49, 52, 54, 57, 59, 62, 65, 67, 70, 73, 76,
+   79, 82, 85, 88, 90, 93, 97,100,103,106,109,112,115,118,121,124};
+
+/* Similar to above, but for an 8-bit gamma-correction table.
+   Copy & paste this snippet into a Python REPL to regenerate:
+import math
+gamma=2.6
+for x in range(256):
+    print("{:3},".format(int(math.pow((x)/255.0,gamma)*255.0+0.5))),
+    if x&15 == 15: print
+*/
+static const uint8_t PROGMEM _NeoPixelGammaTable[256] = {
+    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    0,  0,  0,  0,  0,  0,  0,  0,  1,  1,  1,  1,  1,  1,  1,  1,
+    1,  1,  1,  1,  2,  2,  2,  2,  2,  2,  2,  2,  3,  3,  3,  3,
+    3,  3,  4,  4,  4,  4,  5,  5,  5,  5,  5,  6,  6,  6,  6,  7,
+    7,  7,  8,  8,  8,  9,  9,  9, 10, 10, 10, 11, 11, 11, 12, 12,
+   13, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 20,
+   20, 21, 21, 22, 22, 23, 24, 24, 25, 25, 26, 27, 27, 28, 29, 29,
+   30, 31, 31, 32, 33, 34, 34, 35, 36, 37, 38, 38, 39, 40, 41, 42,
+   42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,
+   58, 59, 60, 61, 62, 63, 64, 65, 66, 68, 69, 70, 71, 72, 73, 75,
+   76, 77, 78, 80, 81, 82, 84, 85, 86, 88, 89, 90, 92, 93, 94, 96,
+   97, 99,100,102,103,105,106,108,109,111,112,114,115,117,119,120,
+  122,124,125,127,129,130,132,134,136,137,139,141,143,145,146,148,
+  150,152,154,156,158,160,162,164,166,168,170,172,174,176,178,180,
+  182,184,186,188,191,193,195,197,199,202,204,206,209,211,213,215,
+  218,220,223,225,227,230,232,235,237,240,242,245,247,250,252,255};
+
+/*! 
+    @brief  Class that stores state and functions for interacting with
+            Adafruit NeoPixels and compatible devices.
+*/
+class Adafruit_NeoPixel {
+
+ public:
+
+  // Constructor: number of LEDs, pin number, LED type
+  Adafruit_NeoPixel(uint16_t n, uint16_t pin=6,
+    neoPixelType type=NEO_GRB + NEO_KHZ800);
+  Adafruit_NeoPixel(void);
+  ~Adafruit_NeoPixel();
+
+  void              begin(void);
+  void              show(void);
+  void              setPin(uint16_t p);
+  void              setPixelColor(uint16_t n, uint8_t r, uint8_t g, uint8_t b);
+  void              setPixelColor(uint16_t n, uint8_t r, uint8_t g, uint8_t b,
+                      uint8_t w);
+  void              setPixelColor(uint16_t n, uint32_t c);
+  void              fill(uint32_t c=0, uint16_t first=0, uint16_t count=0);
+  void              setBrightness(uint8_t);
+  void              clear(void);
+  void              updateLength(uint16_t n);
+  void              updateType(neoPixelType t);
+  /*!
+    @brief   Check whether a call to show() will start sending data
+             immediately or will 'block' for a required interval. NeoPixels
+             require a short quiet time (about 300 microseconds) after the
+             last bit is received before the data 'latches' and new data can
+             start being received. Usually one's sketch is implicitly using
+             this time to generate a new frame of animation...but if it
+             finishes very quickly, this function could be used to see if
+             there's some idle time available for some low-priority
+             concurrent task.
+    @return  1 or true if show() will start sending immediately, 0 or false
+             if show() would block (meaning some idle time is available).
+  */
+  bool canShow(void) {
+    if (endTime > micros()) {
+      endTime = micros();
+    }
+    return (micros() - endTime) >= 300L;
+  }
+  /*!
+    @brief   Get a pointer directly to the NeoPixel data buffer in RAM.
+             Pixel data is stored in a device-native format (a la the NEO_*
+             constants) and is not translated here. Applications that access
+             this buffer will need to be aware of the specific data format
+             and handle colors appropriately.
+    @return  Pointer to NeoPixel buffer (uint8_t* array).
+    @note    This is for high-performance applications where calling
+             setPixelColor() on every single pixel would be too slow (e.g.
+             POV or light-painting projects). There is no bounds checking
+             on the array, creating tremendous potential for mayhem if one
+             writes past the ends of the buffer. Great power, great
+             responsibility and all that.
+  */
+  uint8_t          *getPixels(void) const { return pixels; };
+  uint8_t           getBrightness(void) const;
+  /*!
+    @brief   Retrieve the pin number used for NeoPixel data output.
+    @return  Arduino pin number (-1 if not set).
+  */
+  int16_t           getPin(void) const { return pin; };
+  /*!
+    @brief   Return the number of pixels in an Adafruit_NeoPixel strip object.
+    @return  Pixel count (0 if not set).
+  */
+  uint16_t          numPixels(void) const { return numLEDs; }
+  uint32_t          getPixelColor(uint16_t n) const;
+  /*!
+    @brief   An 8-bit integer sine wave function, not directly compatible
+             with standard trigonometric units like radians or degrees.
+    @param   x  Input angle, 0-255; 256 would loop back to zero, completing
+                the circle (equivalent to 360 degrees or 2 pi radians).
+                One can therefore use an unsigned 8-bit variable and simply
+                add or subtract, allowing it to overflow/underflow and it
+                still does the expected contiguous thing.
+    @return  Sine result, 0 to 255, or -128 to +127 if type-converted to
+             a signed int8_t, but you'll most likely want unsigned as this
+             output is often used for pixel brightness in animation effects.
+  */
+  static uint8_t    sine8(uint8_t x) {
+    return pgm_read_byte(&_NeoPixelSineTable[x]); // 0-255 in, 0-255 out
+  }
+  /*!
+    @brief   An 8-bit gamma-correction function for basic pixel brightness
+             adjustment. Makes color transitions appear more perceptially
+             correct.
+    @param   x  Input brightness, 0 (minimum or off/black) to 255 (maximum).
+    @return  Gamma-adjusted brightness, can then be passed to one of the
+             setPixelColor() functions. This uses a fixed gamma correction
+             exponent of 2.6, which seems reasonably okay for average
+             NeoPixels in average tasks. If you need finer control you'll
+             need to provide your own gamma-correction function instead.
+  */
+  static uint8_t    gamma8(uint8_t x) {
+    return pgm_read_byte(&_NeoPixelGammaTable[x]); // 0-255 in, 0-255 out
+  }
+  /*!
+    @brief   Convert separate red, green and blue values into a single
+             "packed" 32-bit RGB color.
+    @param   r  Red brightness, 0 to 255.
+    @param   g  Green brightness, 0 to 255.
+    @param   b  Blue brightness, 0 to 255.
+    @return  32-bit packed RGB value, which can then be assigned to a
+             variable for later use or passed to the setPixelColor()
+             function. Packed RGB format is predictable, regardless of
+             LED strand color order.
+  */
+  static uint32_t   Color(uint8_t r, uint8_t g, uint8_t b) {
+    return ((uint32_t)r << 16) | ((uint32_t)g <<  8) | b;
+  }
+  /*!
+    @brief   Convert separate red, green, blue and white values into a
+             single "packed" 32-bit WRGB color.
+    @param   r  Red brightness, 0 to 255.
+    @param   g  Green brightness, 0 to 255.
+    @param   b  Blue brightness, 0 to 255.
+    @param   w  White brightness, 0 to 255.
+    @return  32-bit packed WRGB value, which can then be assigned to a
+             variable for later use or passed to the setPixelColor()
+             function. Packed WRGB format is predictable, regardless of
+             LED strand color order.
+  */
+  static uint32_t   Color(uint8_t r, uint8_t g, uint8_t b, uint8_t w) {
+    return ((uint32_t)w << 24) | ((uint32_t)r << 16) | ((uint32_t)g <<  8) | b;
+  }
+  static uint32_t   ColorHSV(uint16_t hue, uint8_t sat=255, uint8_t val=255);
+  /*!
+    @brief   A gamma-correction function for 32-bit packed RGB or WRGB
+             colors. Makes color transitions appear more perceptially
+             correct.
+    @param   x  32-bit packed RGB or WRGB color.
+    @return  Gamma-adjusted packed color, can then be passed in one of the
+             setPixelColor() functions. Like gamma8(), this uses a fixed
+             gamma correction exponent of 2.6, which seems reasonably okay
+             for average NeoPixels in average tasks. If you need finer
+             control you'll need to provide your own gamma-correction
+             function instead.
+  */
+  static uint32_t   gamma32(uint32_t x);
+
+ protected:
+
+#ifdef NEO_KHZ400  // If 400 KHz NeoPixel support enabled...
+  bool              is800KHz;   ///< true if 800 KHz pixels
+#endif
+  bool              begun;      ///< true if begin() previously called
+  uint16_t          numLEDs;    ///< Number of RGB LEDs in strip
+  uint16_t          numBytes;   ///< Size of 'pixels' buffer below
+  int16_t           pin;        ///< Output pin number (-1 if not yet set)
+  uint8_t           brightness; ///< Strip brightness 0-255 (stored as +1)
+  uint8_t          *pixels;     ///< Holds LED color values (3 or 4 bytes each)
+  uint8_t           rOffset;    ///< Red index within each 3- or 4-byte pixel
+  uint8_t           gOffset;    ///< Index of green byte
+  uint8_t           bOffset;    ///< Index of blue byte
+  uint8_t           wOffset;    ///< Index of white (==rOffset if no white)
+  uint32_t          endTime;    ///< Latch timing reference
+#ifdef __AVR__
+  volatile uint8_t *port;       ///< Output PORT register
+  uint8_t           pinMask;    ///< Output PORT bitmask
+#endif
+#if defined(ARDUINO_ARCH_STM32) || defined(ARDUINO_ARCH_ARDUINO_CORE_STM32)
+  GPIO_TypeDef *gpioPort;       ///< Output GPIO PORT
+  uint32_t gpioPin;             ///< Output GPIO PIN
+#endif
+};
+
+#endif // ADAFRUIT_NEOPIXEL_H

src/lib/Adafruit_NeoPixel/CONTRIBUTING.md

+# Contribution Guidelines
+
+This library is the culmination of the expertise of many members of the open source community who have dedicated their time and hard work. The best way to ask for help or propose a new idea is to [create a new issue](https://github.com/adafruit/Adafruit_NeoPixel/issues/new) while creating a Pull Request with your code changes allows you to share your own innovations with the rest of the community.
+
+The following are some guidelines to observe when creating issues or PRs:
+
+- Be friendly; it is important that we can all enjoy a safe space as we are all working on the same project and it is okay for people to have different ideas
+
+- [Use code blocks](https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet#code); it helps us help you when we can read your code! On that note also refrain from pasting more than 30 lines of code in a post, instead [create a gist](https://gist.github.com/) if you need to share large snippets
+
+- Use reasonable titles; refrain from using overly long or capitalized titles as they are usually annoying and do little to encourage others to help :smile:
+
+- Be detailed; refrain from mentioning code problems without sharing your source code and always give information regarding your board and version of the library

src/lib/Adafruit_NeoPixel/COPYING

+                   GNU LESSER GENERAL PUBLIC LICENSE
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+
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+
+
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+the terms and conditions of version 3 of the GNU General Public
+License, supplemented by the additional permissions listed below.
+
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