MH-Z19 auto-calibration setting (#1580 , #1592)

code/espurna/sensor.ino

@@ -638,6 +638,8 @@ void _sensorLoad() {
         MHZ19Sensor * sensor = new MHZ19Sensor();
         sensor->setRX(MHZ19_RX_PIN);
         sensor->setTX(MHZ19_TX_PIN);
+        if (getSetting("mhz19CalibrateAuto", 0).toInt() == 1)
+            sensor->setCalibrateAuto(true);
         _sensors.push_back(sensor);
     }
     #endif

code/espurna/sensors/MHZ19Sensor.h

@@ -78,7 +78,7 @@ class MHZ19Sensor : public BaseSensor {
             _serial = new SoftwareSerial(_pin_rx, _pin_tx, false, 32);
             _serial->enableIntTx(false);
             _serial->begin(9600);
-            calibrateAuto(false);
+            calibrateAuto(_calibrateAuto);
 
             _ready = true;
             _dirty = false;
@@ -139,6 +139,13 @@ class MHZ19Sensor : public BaseSensor {
             _write(buffer);
         }
 
+        void setCalibrateAuto(boolean value) {
+            _calibrateAuto = value;
+            if (_ready) {
+                calibrateAuto(value);
+            }
+        }
+
     protected:
 
         // ---------------------------------------------------------------------
@@ -214,6 +221,7 @@ class MHZ19Sensor : public BaseSensor {
         double _co2 = 0;
         unsigned int _pin_rx;
         unsigned int _pin_tx;
+        bool _calibrateAuto = false;
         SoftwareSerial * _serial = NULL;
 
 };