ESP32_MQ-135_SH1106.ino

//Include the libraries
#include "DHTesp.h"           // DHT Enable
#include <Ticker.h>           // Temperature Sync
#include <MQUnifiedsensor.h>  // MQ135 Enable
#include "SH1106Wire.h"       // OLED SH1106 1.3 Inch Enable
#include <Wire.h>             // SPI Communication Protocol Enable

#ifndef ESP32
#pragma message(THIS EXAMPLE IS FOR ESP32 ONLY!)
#error Select ESP32 board.
#endif

//Definitions
#define board ("ESP-32")          // Development Board
#define Voltage_Resolution 3.3    // VCC
#define pin 15                    // Analog Input 0 of ESP32
#define type "MQ-135"             // MQ135
#define ADC_Bit_Resolution 12     // For ESP32
#define RatioMQ135CleanAir 3.6    // RS / R0 = 3.6 ppm

//Declare Sensor
MQUnifiedsensor MQ135(board, Voltage_Resolution, ADC_Bit_Resolution, pin, type);
SH1106Wire display(0x3c, 21, 22); // OLED instance with address and SDA and SCL pins
DHTesp dht;
void tempTask(void *pvParameters);
bool getTemperature();
void triggerGetTemp();
bool initTemp();

/** Task handle for the light value read task */
TaskHandle_t tempTaskHandle = NULL;
/** Ticker for temperature reading */
Ticker tempTicker;
/** Flag if task should run */
bool tasksEnabled = false;
/** Pin number for DHT11 data pin */
int dhtPin = 17;

/**
 * initTemp
 * Setup DHT library
 * Setup task and timer for repeated measurement
 * @return bool
 *    true if task and timer are started
 *    false if task or timer couldn't be started
 **/
bool initTemp()
{
  byte resultValue = 0;
  // Initialize temperature sensor
	dht.setup(dhtPin, DHTesp::DHT11);
	Serial.println("DHT initiated");

  // Start task to get temperature
	xTaskCreatePinnedToCore
  (
		tempTask,                       /* Function to implement the task */
		"tempTask ",                    /* Name of the task */
		4000,                           /* Stack size in words */
		NULL,                           /* Task input parameter */
		5,                              /* Priority of the task */
		&tempTaskHandle,                /* Task handle. */
		1);                             /* Core where the task should run */

  if (tempTaskHandle == NULL)
  {
    Serial.println("Failed to start task for temperature update");
    return false;
  }
  else
  {
    // Start update of environment data every 5 seconds
    tempTicker.attach(5, triggerGetTemp);
  }
  return true;
}

/**
 * triggerGetTemp
 * Sets flag dhtUpdated to true for handling in loop()
 * called by Ticker getTempTimer
 **/
void triggerGetTemp()
{
  if (tempTaskHandle != NULL)
  {
	   xTaskResumeFromISR(tempTaskHandle);
  }
}

/**
 * Task to reads temperature from DHT11 sensor
 * @param pvParameters
 *    pointer to task parameters
 **/
void tempTask(void *pvParameters)
{
	Serial.println("tempTask loop started");
	while (1) // tempTask loop
  {
    if (tasksEnabled)
    {
      // Get temperature values
			getTemperature();
		}
    // Got sleep again
		vTaskSuspend(NULL);
	}
}

/**
 * getTemperature
 * Reads temperature from DHT11 sensor
 * @return bool
 *    true if temperature could be aquired
 *    false if aquisition failed
**/
bool getTemperature() {
	// Reading temperature for humidity takes about 250 milliseconds!
	// Sensor readings may also be up to 2 seconds 'old' (it's a very slow sensor)
  TempAndHumidity newValues = dht.getTempAndHumidity();
	// Check if any reads failed and exit early (to try again).
	if (dht.getStatus() != 0) {
		Serial.println("DHT11 error status: " + String(dht.getStatusString()));
		return false;
	}

  display.clear();
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 0, "IoT" );
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 14, "MONITORING DEVICE" );
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 28, "Temperature : " + String(newValues.temperature) + " °C" );
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 42, "Humidity : " + String(newValues.humidity) + " %" );
  display.display();
  return true;
}

void setup()
{
  //Init the serial port communication - to debug the library
  Serial.begin(115200);
  Wire.begin();
  display.init();
  display.setFont(ArialMT_Plain_10);
  display.invertDisplay();
  display.flipScreenVertically();
  //Set math model to calculate the PPM concentration and the value of constants
  MQ135.setRegressionMethod(1); //_PPM =  a*ratio^b
  MQ135.setA(110.47); MQ135.setB(-2.862); // Configure the equation to to calculate C02 concentration
  
  /*
    Exponential regression:
  GAS      | a      | b
  CO       | 605.18 | -3.937  
  Alcohol  | 77.255 | -3.18 
  CO2      | 110.47 | -2.862
  Toluen   | 44.947 | -3.445
  NH4      | 102.2  | -2.473
  Aceton   | 34.668 | -3.369
  */
  
  MQ135.init(); 
  Serial.print("Calibrating please wait.");
  float calcR0 = 0;
  for(int i = 1; i<=10; i ++)
  {
    MQ135.update(); // Update data, the arduino will read the voltage from the analog pin
    calcR0 += MQ135.calibrate(RatioMQ135CleanAir);
    Serial.print(".");
  }
  MQ135.setR0(calcR0/10);
  Serial.println("  done!.");
  
  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
  MQ135.serialDebug(true);

  Serial.println();
  Serial.println("DHT ESP32 example with tasks");
  initTemp();
  // Signal end of setup() to tasks
  tasksEnabled = true;
}

void loop()
{
  if (!tasksEnabled)
  {
    // Wait 2 seconds to let system settle down    
    // Enable task that will read values from the DHT sensor
    tasksEnabled = true;
    if (tempTaskHandle != NULL)
    {
			vTaskResume(tempTaskHandle);
		}
  }

  yield();
  printDisplay();
  delay(5000);
}


void drawProgressBarDemo()
{
  float NH4, CO2, ALC;
  for(int i = 0; i<=3; i++)
  {
    switch (i)
    {
     case 1:
            MQ135.setA(110.47); MQ135.setB(-2.862); // Configure the equation to to calculate C02 concentration
            MQ135.update(); // Update data, the arduino will read the voltage from the analog pin
            MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
            CO2 = MQ135.ppmprint(1);
            Serial.print("CO2 : ");
            break;
     case 2:
            MQ135.setA(102.2); MQ135.setB(-2.473); // Configure the equation to to calculate NH4 concentration
            MQ135.update(); // Update data, the arduino will read the voltage from the analog pin
            MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
            NH4 = MQ135.ppmprint(1);
            Serial.print("NH4 : ");
            break;  
    }
  }
  
  // MQ135.update(); // Update data, the arduino will read the voltage from the analog pin
  // MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup

  // float h = lightMeter.readLightLevel();
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 0, "IoT" );
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 14, "MONITORING DEVICE" );
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 28, "CO2 : "+ String(CO2) + " PPM" );
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(64, 42, "NH4 : " + String(NH4) + " PPM" );  
}

void printDisplay()
{
  display.clear();
  drawProgressBarDemo();
  display.display();  
}