Merge branch 'develop'

983003b4 · Eric Duminil · a200c6f8 · 86309b4a · 983003b4 · 983003b4
Commit 983003b4 authored Jan 04, 2021 by Eric Duminil
--- a/README.md
+++ b/README.md
@@ -6,6 +6,18 @@ It measures the current CO<sub>2</sub> concentration (in ppm), and displays it o

 The room should be ventilated as soon as one LED turns red.

+## Features
+
+The *CO<sub>2</sub> Ampel* can:
+
+* Display CO2 concentration on LED ring.
+* Allow calibration.
+* Get current time over NTP
+* Send data over MQTT.
+* Send data over LoRaWAN.
+* Display measurements and configuration on a small website.
+* Log data to a CSV file, directly on the ESP flash memory.
+
 ## 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*)

--- a/ampel-firmware.h
+++ b/ampel-firmware.h
@@ -5,25 +5,33 @@
 *****************************************************************/
 #include "config.h"
 #ifndef MEASUREMENT_TIMESTEP
-#  error Missing config.h file. Please copy config.example.h to config.h.
+#  error Missing config.h file. Please copy config.public.h to config.h.
 #endif
-#ifdef MQTT
-#  include "mqtt.h"
+
+#ifdef AMPEL_CSV
+#  include "csv_writer.h"
 #endif

-#include "util.h"
-#include "wifi_util.h"
-#include "co2_sensor.h"
+#ifdef AMPEL_WIFI
+#  include "wifi_util.h"
+#  ifdef AMPEL_MQTT
+#    include "mqtt.h"
+#  endif
+#  ifdef AMPEL_HTTP
+#    include "web_server.h"
+#  endif
+#endif

-#ifdef HTTP
-#  include "web_server.h"
+#ifdef AMPEL_LORAWAN
+#  include "lorawan.h"
 #endif

+#include "util.h"
+#include "co2_sensor.h"
 #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
+//allows sensor to be seen as SENSOR_ID.local, from the local network. For example : espd03cc5.local
 #  include <ESP8266mDNS.h>
 #elif defined(ESP32)
 #  include <ESPmDNS.h>

--- a/ampel-firmware.ino
+++ b/ampel-firmware.ino
@@ -59,14 +59,14 @@
 * Setup                                                         *
 *****************************************************************/
 void setup() {
-  LedEffects::setupOnBoardLED();
-  LedEffects::onBoardLEDOff();
+  led_effects::setupOnBoardLED();
+  led_effects::onBoardLEDOff();

  Serial.begin(BAUDS);

-  pinMode(0, INPUT);  // Flash button (used for forced calibration)
+  pinMode(0, INPUT); // Flash button (used for forced calibration)

-  LedEffects::setupRing();
+  led_effects::setupRing();

  sensor::initialize();

@@ -75,6 +75,7 @@ void setup() {
  Serial.print(F("Board    : "));
  Serial.println(BOARD);

+#ifdef AMPEL_WIFI
  // Try to connect to Wi-Fi
  WiFiConnect(SENSOR_ID);

@@ -82,9 +83,9 @@ void setup() {
  Serial.println(WiFi.status());

  if (WiFi.status() == WL_CONNECTED) {
-#ifdef HTTP
+#  ifdef AMPEL_HTTP
    web_server::initialize();
-#endif
+#  endif

    ntp::initialize();

@@ -95,11 +96,19 @@ void setup() {
      Serial.println(F("Error setting up MDNS responder!"));
    }

-#ifdef MQTT
+#  ifdef AMPEL_MQTT
    mqtt::initialize("CO2sensors/" + SENSOR_ID);
-#endif
+#  endif
  }
+#endif
+
+#ifdef AMPEL_CSV
  csv_writer::initialize();
+#endif
+
+#if defined(AMPEL_LORAWAN) && defined(ESP32)
+  lorawan::initialize();
+#endif
 }

 /*****************************************************************
@@ -107,73 +116,36 @@ void setup() {
 *****************************************************************/

 void loop() {
+#if defined(AMPEL_LORAWAN) && defined(ESP32)
+  //LMIC Library seems to be very sensitive to timing issues, so run it first.
+  lorawan::process();
+
+  if (lorawan::waiting_for_confirmation) {
+    // If node is waiting for join confirmation from Gateway, nothing else should run.
+    return;
+  }
+#endif
  //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);
-
+  if (sensor::processData()) {
+#ifdef AMPEL_CSV
    csv_writer::logIfTimeHasCome(sensor::timestamp, sensor::co2, sensor::temperature, sensor::humidity);
+#endif

-#ifdef MQTT
+#if defined(AMPEL_WIFI) && defined(AMPEL_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();
+#if defined(AMPEL_LORAWAN) && defined(ESP32)
+    lorawan::preparePayloadIfTimeHasCome(sensor::co2, sensor::temperature, sensor::humidity);
+#endif
  }

  uint32_t duration = millis() - t0;
@@ -193,34 +165,36 @@ void loop() {
 */
 void checkFlashButton() {
  if (!digitalRead(0)) { // Button has been pressed
-    LedEffects::onBoardLEDOn();
+    led_effects::onBoardLEDOn();
    delay(300);
    if (digitalRead(0)) {
      Serial.println(F("Flash has been pressed for a short time. Should toggle night mode."));
-      LedEffects::toggleNightMode();
+      led_effects::toggleNightMode();
    } else {
      Serial.println(F("Flash has been pressed for a long time. Keep it pressed for calibration."));
-      if (LedEffects::countdownToZero() < 0) {
+      if (led_effects::countdownToZero() < 0) {
        sensor::startCalibrationProcess();
      }
    }
-    LedEffects::onBoardLEDOff();
+    led_effects::onBoardLEDOff();
  }
 }

 void keepServicesAlive() {
+#ifdef AMPEL_WIFI
  if (WiFi.status() == WL_CONNECTED) {
-#if defined(ESP8266)
+#  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
+#  endif
    ntp::update(); // NTP client has its own timer. It will connect to NTP server every 60s.
-#ifdef HTTP
+#  ifdef AMPEL_HTTP
    web_server::update();
-#endif
-#ifdef MQTT
+#  endif
+#  ifdef AMPEL_MQTT
    mqtt::keepConnection(); // MQTT client has its own timer. It will keep alive every 15s.
-#endif
+#  endif
  }
+#endif
 }
--- a/co2_sensor.cpp
+++ b/co2_sensor.cpp
@@ -2,17 +2,17 @@

 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]
+  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]
+  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]
+  const bool auto_calibrate_sensor = AUTO_CALIBRATE_SENSOR; // [true / false]
 }

 namespace sensor {
@@ -21,13 +21,16 @@ namespace sensor {
  float temperature = 0;
  float humidity = 0;
  String timestamp = "";
+  int16_t stable_measurements = 0;
+  uint32_t waiting_color = color::blue;
+  bool should_calibrate = false;

  void initialize() {
 #if defined(ESP8266)
    Wire.begin(12, 14);  // ESP8266 - D6, D5;
 #endif
 #if defined(ESP32)
-    Wire.begin(21, 22);  // ESP32
+    Wire.begin(21, 22); // ESP32
    /**
     *  SCD30   ESP32
     *  VCC --- 3V3
@@ -41,46 +44,146 @@ namespace sensor {
    if (scd30.begin(config::auto_calibrate_sensor) == false) {
      Serial.println("Air sensor not detected. Please check wiring. Freezing...");
      while (1) {
-        LedEffects::showWaitingLED(color::red);
+        led_effects::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]
+    //NOTE: The timer seems to be inaccurate, though, possibly depending on voltage. Should it be offset?
+    Serial.println();
+    Serial.print(F("Setting SCD30 timestep to "));
+    Serial.print(config::measurement_timestep);
+    Serial.println(" s.");
+    scd30.setMeasurementInterval(config::measurement_timestep); // [s]

-    Serial.print("Setting temperature offset to -");
+    Serial.print(F("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.
+    delay(100);

-    Serial.print("Temperature offset is : -");
+    Serial.print(F("Temperature offset is : -"));
    Serial.print(scd30.getTemperatureOffset());
    Serial.println(" K");

-    Serial.print("Auto-calibration is ");
+    Serial.print(F("Auto-calibration is "));
    Serial.println(config::auto_calibrate_sensor ? "ON." : "OFF.");
  }

-// Force SCD30 calibration with countdown.
+  //NOTE: should timer deviation be used to adjust measurement_timestep?
+  void checkTimerDeviation() {
+    static int32_t previous_measurement_at = 0;
+    int32_t now = millis();
+    Serial.print("Measurement time offset : ");
+    Serial.print(now - previous_measurement_at - config::measurement_timestep * 1000);
+    Serial.println(" ms.");
+    previous_measurement_at = now;
+  }
+
+  void countStableMeasurements() {
+    static int16_t previous_co2 = 0;
+    if (co2 > (previous_co2 - 30) && co2 < (previous_co2 + 30)) {
+      stable_measurements++;
+      Serial.print(F("Number of stable measurements : "));
+      Serial.println(stable_measurements);
+      waiting_color = color::green;
+    } else {
+      stable_measurements = 0;
+      waiting_color = color::red;
+    }
+    previous_co2 = co2;
+  }
+
  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...");
+    Serial.println(F("Setting SCD30 timestep to 2s, prior to calibration."));
+    scd30.setMeasurementInterval(2); // [s] The change will only take effect after next measurement.
+    Serial.println(F("Waiting until the measurements are stable for at least 2 minutes."));
+    Serial.println(F("It could take a very long time."));
+    should_calibrate = true;
+  }
+
+  void calibrateAndRestart() {
+    Serial.print(F("Calibrating SCD30 now..."));
    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();
+    Serial.println(F(" Done!"));
+    Serial.println(F("Sensor calibrated."));
+    ESP.restart(); // softer than ESP.reset
+  }
+
+  void logToSerial() {
+    Serial.println(timestamp);
+    Serial.print(F("co2(ppm): "));
+    Serial.print(co2);
+    Serial.print(F(" temp(C): "));
+    Serial.print(temperature, 1);
+    Serial.print(F(" humidity(%): "));
+    Serial.println(humidity, 1);
+  }
+
+  void displayCO2OnLedRing() {
+    if (co2 < 250) {
+      // Sensor should be calibrated.
+      led_effects::showWaitingLED(color::magenta);
+      return;
+    }
+    /**
+     * Display data, even if it's "old" (with breathing).
+     * Those effects include a short delay.
+     */
+    if (co2 < 2000) {
+      led_effects::displayCO2color(co2);
+      led_effects::breathe(co2);
+    } else {
+      // >= 2000: entire ring blinks red
+      led_effects::redAlert();
+    }
+  }
+
+  /** Gets fresh data if available, checks calibration status, displays CO2 levels.
+   * Returns true if fresh data is available, for further processing (e.g. MQTT, CSV or LoRa)
+   */
+  bool processData() {
+    bool freshData = scd30.dataAvailable();
+
+    if (freshData) {
+      // checkTimerDeviation();
+      timestamp = ntp::getLocalTime();
+      co2 = scd30.getCO2();
+      temperature = scd30.getTemperature();
+      humidity = 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 (co2 <= 0) {
+      // No measurement yet. Waiting.
+      led_effects::showWaitingLED(color::blue);
+      return false;
+    }
+
+    /**
+     * Fresh data. Log it and send it if needed.
+     */
+    if (freshData) {
+      if (should_calibrate) {
+        countStableMeasurements();
+      }
+      logToSerial();
+    }
+
+    if (should_calibrate) {
+      if (stable_measurements == 60) {
+        calibrateAndRestart();
+      }
+      led_effects::showWaitingLED(waiting_color);
+      return false;
+    }
+
+    displayCO2OnLedRing();
+    return freshData;
  }
 }
--- a/co2_sensor.h
+++ b/co2_sensor.h
@@ -6,13 +6,13 @@
 #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 "util.h"
 #include <Wire.h>

 namespace config {
-  extern uint16_t measurement_timestep;  // [s] Value between 2 and 1800 (range for SCD30 sensor)
+  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 uint16_t co2_calibration_level; // [ppm]
  extern const float temperature_offset; // [K] Sign isn't relevant.
 }

@@ -24,6 +24,7 @@ namespace sensor {
  extern String timestamp;

  void initialize();
+  bool processData();
  void startCalibrationProcess();
 }
 #endif
--- a/config.public.h
+++ b/config.public.h
@@ -3,14 +3,24 @@

 // This file is a config template, and can be copied to config.h. Please don't save any important password in this template.

+/**
+ * SERVICES
+ */
+
+// Comment or remove those lines if you want to disable the corresponding services
+#  define AMPEL_WIFI    // Should ESP connect to WiFi? It allows the Ampel to get time from an NTP server.
+#  define AMPEL_HTTP    // Should HTTP web server be started? (AMPEL_WIFI should be enabled too)
+#  define AMPEL_MQTT    // Should data be sent over MQTT? (AMPEL_WIFI should be enabled too)
+#  define AMPEL_CSV     // Should data be logged as CSV, on the ESP flash memory?
+// #  define AMPEL_LORAWAN // Should data be sent over LoRaWAN? (Requires ESP32 + LoRa modem, and "MCCI LoRaWAN LMIC library")
+
 /**
 * 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_SSID     "MY_SSID"
 #  define WIFI_PASSWORD "P4SSW0RD"
-#  define WIFI_TIMEOUT  20 // [s]
+#  define WIFI_TIMEOUT  30 // [s]

 /**
 * Sensor
@@ -20,15 +30,10 @@
 //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
+// WARNING: Writing too often might damage the ESP memory
 #  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?
@@ -64,29 +69,26 @@
 * 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
+ * MQTT
 */
-#  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.
+ * If AMPEL_MQTT is enabled, co2ampel will publish data every MQTT_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}
+ *  CO2sensors/ESPd03cc5 {"time":"2020-12-13 13:14:37+01", "co2":571, "temp":18.9, "rh":50.9}
+ *  CO2sensors/ESPd03cc5 {"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}
+ *  CO2sensors/ESPd03cc5 {"time":"2020-12-13 13:15:09+01", "co2":568, "temp":18.9, "rh":50.1}
+ *  CO2sensors/ESPd03cc5 {"time":"2020-12-13 13:15:20+01", "co2":572, "temp":18.9, "rh":50.3}
 *  ...
 */

@@ -98,12 +100,45 @@
 */
 #  define ALLOW_MQTT_COMMANDS false

+// 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 MQTT_SENDING_INTERVAL MEASUREMENT_TIMESTEP * 5 // [s]
+#  define MQTT_SENDING_INTERVAL 60 // [s]
 #  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

+/**
+ * LoRaWAN
+ */
+
+// 1) Requires "MCCI LoRaWAN LMIC library", which will be automatically used with PlatformIO but should be added in "Arduino IDE".
+// 2) Region and transceiver type should be specified in:
+//     * Arduino/libraries/MCCI_LoRaWAN_LMIC_library/project_config/lmic_project_config.h for Arduino IDE
+//     * platformio.ini for PlatformIO
+//    See https://github.com/mcci-catena/arduino-lmic#configuration for more information
+// 3) It has been tested with "TTGO ESP32 SX1276 LoRa 868" and will only work with an ESP32 + LoRa modem
+// 4) In order to use LoRaWAN, a gateway should be close to the co2ampel, and an account, an application and a device should be registered,
+//      e.g. on https://www.thethingsnetwork.org/docs/applications/
+// 5) The corresponding keys should be defined in LORAWAN_DEVICE_EUI, LORAWAN_APPLICATION_EUI and LORAWAN_APPLICATION_KEY
+// How often should measurements be sent over LoRaWAN?
+#  define LORAWAN_SENDING_INTERVAL 300 // [s] This value should not be too low. See https://www.thethingsnetwork.org/docs/lorawan/duty-cycle.html#maximum-duty-cycle
+
+// WARNING: If AMPEL_LORAWAN is enabled, you need to modify the 3 following constants!
+// This EUI must be in little-endian format, so least-significant-byte first.
+// When copying an EUI from ttnctl output, this means to reverse the bytes.
+#  define LORAWAN_DEVICE_EUI      {0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11}
+// This should also be in little endian format, see above.
+// For TheThingsNetwork issued EUIs the last bytes should be 0xD5, 0xB3, 0x70.
+#  define LORAWAN_APPLICATION_EUI {0x00, 0x00, 0x00, 0x00, 0x00, 0xD5, 0xB3, 0x70}
+// This key should be in big endian format (or, since it is not really a
+// number but a block of memory, endianness does not really apply). In
+// practice, a key taken from ttnctl can be copied as-is.
+#  define LORAWAN_APPLICATION_KEY {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
+
 /**
 * NTP
 */

--- a/csv_writer.cpp
+++ b/csv_writer.cpp
 #include "csv_writer.h"