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();
  }
}