Added MQ135-ADS1115 example and feature

examples/MQ135-ADS1115/MQ135-ADS1115.ino

@@ -0,0 +1,124 @@
+/*
+  MQUnifiedsensor Library - reading an MQ135
+  Demonstrates the use a MQ135 sensor.
+  Library originally added 01 may 2019
+  by Miguel A Califa, Yersson Carrillo, Ghiordy Contreras, Mario Rodriguez
+ 
+  Added example
+  modified 20 March 2022
+  by Miguel Califa 
+  
+  Wiring:
+  https://github.com/miguel5612/MQSensorsLib_Docs/blob/master/static/img/MQ_Arduino.PNG
+  Please make sure arduino A0 pin represents the analog input configured on #define pin
+ This example code is in the public domain.
+
+  Library link https://github.com/adafruit/Adafruit_ADS1X15
+*/
+#include <Wire.h>
+#include <Adafruit_ADS1X15.h>
+//Include the library
+#include <MQUnifiedsensor.h>
+//Definitions
+#define placa "Arduino UNO"
+#define type "MQ-135" //MQ135
+#define RatioMQ135CleanAir 3.6//RS / R0 = 3.6 ppm  
+float factorEscala = 0.1875F;
+//#define calibration_button 13 //Pin to calibrate your sensor
+//Declare Sensor
+MQUnifiedsensor MQ135(placa, type);
+
+ 
+// Crear objeto de la clase
+Adafruit_ADS1115 ads;
+ 
+void setup(void) 
+{
+ //Init the serial port communication - to debug the library
+  Serial.begin(9600); //Init serial port
+  delay(200);
+
+  //Set math model to calculate the PPM concentration and the value of constants
+  MQ135.setRegressionMethod(1); //_PPM =  a*ratio^b
+
+  /************************************************************************************/ 
+  MQ135.init(); 
+ 
+  // Iniciar el ADS1115
+  ads.begin();
+
+
+  Serial.print("Calibrating please wait.");
+  float calcR0 = 0;
+  for(int i = 1; i<=10; i ++)
+  {
+    // Obtener datos del A0 del ADS1115
+    short adc0 = ads.readADC_SingleEnded(0);
+    float voltios = (adc0 * factorEscala)/1000.0;
+    MQ135.externalADCUpdate(voltios); // 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);}
+  /*****************************  MQ CAlibration ********************************************/ 
+  Serial.println("** Values from MQ-135 ****");
+  Serial.println("|    CO   |  Alcohol |   CO2  |  Toluen  |  NH4  |  Aceton  |");  
+}
+ 
+void loop() {
+// Obtener datos del A0 del ADS1115
+  short adc0 = ads.readADC_SingleEnded(0);
+  float voltios = (adc0 * factorEscala)/1000.0;
+  MQ135.externalADCUpdate(voltios); // Update data, the arduino will read the voltage from the analog pin
+
+  MQ135.setA(605.18); MQ135.setB(-3.937); // Configure the equation to calculate CO concentration value
+  float CO = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
+
+  MQ135.setA(77.255); MQ135.setB(-3.18); //Configure the equation to calculate Alcohol concentration value
+  float Alcohol = MQ135.readSensor(); // SSensor will read PPM concentration using the model, a and b values set previously or from the setup
+
+  MQ135.setA(110.47); MQ135.setB(-2.862); // Configure the equation to calculate CO2 concentration value
+  float CO2 = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
+
+  MQ135.setA(44.947); MQ135.setB(-3.445); // Configure the equation to calculate Toluen concentration value
+  float Tolueno = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
+
+  MQ135.setA(102.2 ); MQ135.setB(-2.473); // Configure the equation to calculate NH4 concentration value
+  float NH4 = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
+
+  MQ135.setA(34.668); MQ135.setB(-3.369); // Configure the equation to calculate Aceton concentration value
+  float Acetona = MQ135.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
+  Serial.print("|   "); Serial.print(CO); 
+  Serial.print("   |   "); Serial.print(Alcohol);
+  // Note: 200 Offset for CO2 source: https://github.com/miguel5612/MQSensorsLib/issues/29
+
+    
+        
+  /*
+  Motivation:
+  We have added 200 PPM because when the library is calibrated it assumes the current state of the
+  air as 0 PPM, and it is considered today that the CO2 present in the atmosphere is around 400 PPM.
+  https://www.lavanguardia.com/natural/20190514/462242832581/concentracion-dioxido-cabono-co2-atmosfera-bate-record-historia-humanidad.html
+  */
+  Serial.print("   |   "); Serial.print(CO2 + 400); 
+  Serial.print("   |   "); Serial.print(Tolueno); 
+  Serial.print("   |   "); Serial.print(NH4); 
+  Serial.print("   |   "); Serial.print(Acetona);
+  Serial.println("   |"); 
+  /*
+    Exponential regression:
+  GAS      | a      | b
+  CO       | 605.18 | -3.937  
+  Alcohol  | 77.255 | -3.18 
+  CO2      | 110.47 | -2.862
+  Tolueno  | 44.947 | -3.445
+  NH4      | 102.2  | -2.473
+  Acetona  | 34.668 | -3.369
+  */
+
+  delay(500); //Sampling frequency
+}

src/MQUnifiedsensor.cpp

@@ -9,6 +9,10 @@ MQUnifiedsensor::MQUnifiedsensor(String Placa, float Voltage_Resolution, int ADC
   this-> _VOLT_RESOLUTION = Voltage_Resolution;
   this-> _ADC_Bit_Resolution = ADC_Bit_Resolution;
 }
+MQUnifiedsensor::MQUnifiedsensor(String Placa, String type) {
+  Placa.toCharArray(this->_placa, 20);
+  type.toCharArray(this->_type, 6);
+}
 void MQUnifiedsensor::init()
 {
   pinMode(_pin, INPUT);
@@ -108,6 +112,10 @@ void MQUnifiedsensor::update()
 {
   _sensor_volt = this->getVoltage();
 }
+void MQUnifiedsensor::externalADCUpdate(float volt)
+{
+  _sensor_volt = volt;
+}
 float MQUnifiedsensor::validateEcuation(float ratioInput)
 {
   //Serial.print("Ratio input: "); Serial.println(ratioInput);

src/MQUnifiedsensor.h

@@ -14,10 +14,12 @@ class MQUnifiedsensor
 {
   public:
     MQUnifiedsensor(String Placa = "Arduino", float Voltage_Resolution =  5, int ADC_Bit_Resolution = 10, int pin = 1, String type = "CUSTOM MQ");
+    MQUnifiedsensor(String Placa = "Arduino", String type = "CUSTOM MQ");
     
     //Functions to set values
     void init();
     void update();
+    void externalADCUpdate(float volt);
     void setR0(float R0 = 10);
     void setRL(float RL = 10);
     void setA(float a);