Include coeficient tables to library

[Nic30]

I would like to avoid duplication of constant in my project. What I did is to copy A,B interpolation coefficients from examples.

There are 2 things which can be done. 1st is to include some array which will contain coefficients or there could be class for every gas sensor with a proper method. Second variant seems to me as better because it is faster and intuitive.

class MQ2GasSensor: public MQGasSensor {
public:
  static const float CLEAN_AIR_PPM = 9.83; // RS / R0
  using MQGasSensor::MQGasSensor;
  
  float getPpmH2() {
     return getInterpolation(987.99, -2.162);
  }
  float getPpmLPG() {
     return getInterpolation(574.25, -2.222);
  }
// ...
}

[miguel5612]

it could be like:

`class MQ2GasSensor : public MQUnifiedsensor {
public:
MQ2GasSensor(const char* board, float voltageResolution, int bitResolution, int pin, const char* type)
: MQUnifiedsensor(board, voltageResolution, bitResolution, pin, type) {}

float getPpmH2() {
    setA(987.99);
    setB(-2.162);
    return readSensor();
}

float getPpmLPG() {
    setA(574.25);
    setB(-2.222);
    return readSensor();
}

float getPpmCO() {
    setA(36974);
    setB(-3.109);
    return readSensor();
}

float getPpmAlcohol() {
    setA(3616.1);
    setB(-2.675);
    return readSensor();
}

float getPpmPropane() {
    setA(658.71);
    setB(-2.168);
    return readSensor();
}

};`

Could you reply to all examples, and send us the pull or merge request? @Nic30
Thanks ;)