air_quality_sensor.ino

#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7789.h> // Hardware-specific library for ST7789
#include <SPI.h>

// Use dedicated hardware SPI pins
Adafruit_ST7789 tft = Adafruit_ST7789(TFT_CS, TFT_DC, TFT_RST);

//Battery Monitor 
#include "Adafruit_MAX1704X.h"
Adafruit_MAX17048 maxlipo;

//SCD40 air sensor
#include <Wire.h>
#include "SparkFun_SCD4x_Arduino_Library.h" 
SCD4x mySensor;
#include <Arduino.h>
#include <SensirionI2CScd4x.h>
#include <Wire.h>
SensirionI2CScd4x scd4x;

//SGP MOX gas sensor
#include "Adafruit_SGP40.h"
#include "Adafruit_SHT31.h"
Adafruit_SGP40 sgp;
Adafruit_SHT31 sht31;


struct battery_val {
  float volt;
  float percent;
};

struct air_val {
  uint16_t co2;
  float temperature;
  float relative_humidity;
};

struct voc_val {
  uint16_t sraw;
  int32_t voc_index;
};

struct air_val get_air_values() {
  uint16_t error;
  char errorMessage[256];
  struct air_val air_values;


  error = scd4x.readMeasurement(air_values.co2, air_values.temperature, air_values.relative_humidity);
  if (error) {
    Serial.print("Error trying to execute readMeasurement(): ");
    errorToString(error, errorMessage, 256);
    Serial.println(errorMessage);
  } else if (air_values.co2 == 0) {
      Serial.println("Invalid sample detected, skipping.");
  } 

  return air_values;
}

struct voc_val get_voc(float temperature, float relative_humidity) {
  // Get VOC index
  struct voc_val voc_values;

  voc_values.sraw = sgp.measureRaw(temperature, relative_humidity);

  Serial.print("Raw measurement: ");
  Serial.println(voc_values.sraw);

  voc_values.voc_index = sgp.measureVocIndex(temperature, relative_humidity);
  Serial.print("Voc Index: ");
  Serial.println(voc_values.voc_index);

  return voc_values;
}

void updateTFT(float temp, float humidity, uint16_t co_two, int32_t voc_index, uint16_t voc_raw , float batt_volt, float batt_perc) {
  int text_size = 2;
  tft.setTextSize(text_size);

  tft.setCursor(0, 0);
  tft.fillScreen(ST77XX_BLACK);
  
  tft.setTextColor(ST77XX_WHITE);
  tft.print(F("Temp: ")); tft.print(temp); tft.println(" C");
  tft.print(F("Temp: ")); tft.print( ((temp*9)/5) + 32); tft.println(" F");

  tft.setTextColor(ST77XX_YELLOW);
  tft.print(F("Rel Humidity: ")); tft.print(humidity); tft.println(" %");

  tft.setTextColor(ST77XX_GREEN);
  tft.print(F("CO2:")); tft.print(co_two); tft.println(" ppm");
  
  tft.setTextColor(ST77XX_BLUE);
  //tft.print("VOC: "); tft.print(voc_raw); tft.println(" ppm");
  tft.print("VOC Raw: "); tft.println(voc_raw);
  tft.print("VOC Index: "); tft.println(voc_index);


  tft.setTextColor(ST77XX_ORANGE);
  tft.print(F("Batt Voltage: ")); tft.print(batt_volt,1); tft.println(" V");
  tft.print(F("Batt Charge:  ")); tft.print(batt_perc,1); tft.println(" %");  
}


void setup(void) {
  Serial.begin(9600);
  /*
  while (!Serial) {
        delay(100);
  }
  */
  Serial.println(F("Serial Terminal Initialized"));

  Serial.println(F("Starting Initialization of TFT Display"));
  // turn on backlite
  pinMode(TFT_BACKLITE, OUTPUT);
  digitalWrite(TFT_BACKLITE, HIGH);

  // turn on the TFT / I2C power supply
  pinMode(TFT_I2C_POWER, OUTPUT);
  digitalWrite(TFT_I2C_POWER, HIGH);
  delay(10);

  // initialize TFT
  tft.init(135, 240); // Init ST7789 240x135
  tft.setRotation(3);
  tft.fillScreen(ST77XX_BLACK);

  //Configure tft
  tft.setTextWrap(false);
  Serial.println(F("Initialized TFT Display"));

  ////////////////////////////////////////
  //check for battery
  if (!maxlipo.begin()) {
    Serial.println(F("Couldnt find Adafruit MAX17048?\nMake sure a battery is plugged in!"));
    while (1) delay(10);
  }
  Serial.print(F("Found MAX17048")); Serial.print(F(" with Chip ID: 0x")); Serial.println(maxlipo.getChipID(), HEX);
  ////////////////////////////////////////

  ////////////////////////////////////////
  // Initialize SCD40
  Serial.println(F("Starting Initialization of SC40 Air Sensor"));
  Wire.begin();

  uint16_t error;
  char errorMessage[256];

  scd4x.begin(Wire);

  // stop potentially previously started measurement
  error = scd4x.stopPeriodicMeasurement();
  if (error) {
    Serial.print("Error trying to execute stopPeriodicMeasurement(): ");
    errorToString(error, errorMessage, 256);
    Serial.println(errorMessage);
  }
  ////////////////////////////////////////

  ////////////////////////////////////////
  // Initialize SCD40
  Serial.println(F("Starting Initialization of SC40 Air Sensor"));
  uint16_t serial0;
  uint16_t serial1;
  uint16_t serial2;
  error = scd4x.getSerialNumber(serial0, serial1, serial2);
  if (error) {
    Serial.print("Error trying to execute getSerialNumber(): ");
    errorToString(error, errorMessage, 256);
    Serial.println(errorMessage);
  } 

  // Start Measurement
  error = scd4x.startPeriodicMeasurement();
  if (error) {
    Serial.print("Error trying to execute startPeriodicMeasurement(): ");
    errorToString(error, errorMessage, 256);
    Serial.println(errorMessage);
  }
  //delay(5000);
  Serial.println(F("Initialized of SC40 Air Sensor"));
  ////////////////////////////////////////

  ////////////////////////////////////////
  // Start the MOX sensoe
    Serial.println("SGP40 test with SHT31 compensation, it takes time to start and get enough values");

  if (! sgp.begin()){
    Serial.println("SGP40 sensor not found :(");
    while (1);
  }

  if (! sht31.begin(0x44)) {   // Set to 0x45 for alternate i2c addr
  //if (! sht31.begin(0x45)) {   // Set to 0x45 for alternate i2c addr
    
    Serial.println("Couldn't find SHT31");
  //  while (1);
  }

  Serial.print("Found SHT3x + SGP40 serial #");
  Serial.print(sgp.serialnumber[0], HEX);
  Serial.print(sgp.serialnumber[1], HEX);
  Serial.println(sgp.serialnumber[2], HEX);
  ////////////////////////////////////////
  
  delay(5000);
  Serial.println("done");
}


void loop() {

  struct battery_val battery;
  struct air_val air;
  struct voc_val voc_values;

  // get batter status
  battery.volt = maxlipo.cellVoltage();
  battery.percent = maxlipo.cellPercent();
 
  air = get_air_values();
  voc_values = get_voc(air.temperature, air.relative_humidity);

  //Update display
  updateTFT(air.temperature,air.relative_humidity,air.co2,voc_values.voc_index,voc_values.sraw,battery.volt,battery.percent);

  delay(5000);
  
}