 
 #define RF95_FREQ 868.0
 
-#define PIN_SENSOR_LIGHT A0
+#define PIN_SENSOR_GND 8
+#define PIN_SENSOR_VCC 7
 #define PIN_SENSOR_SOIL A2
 
 

}

uint16_t readLight(uint16_t vcc) {
  // Can't use a simple LDR as it will use 4.5mA
  // @link https://learn.adafruit.com/photocells/using-a-photocell
  // Maybe a lux meter - https://www.adafruit.com/product/439
  
  return 0;
}

uint16_t readSoil(uint16_t vcc) {


  // Read the temperature while the aref settles.
  tx_payload.setTemperature(readTemperature());

  // Connect the light sensor to ground.
  pinMode(PIN_SENSOR_GND, OUTPUT);
  digitalWrite(PIN_SENSOR_GND, LOW);

  // Power up the soil sensor.
  digitalWrite(PIN_SENSOR_GND, HIGH);
  
  tx_payload.setChargeMa(readSolarCurrent());
  tx_payload.setChargeMv(readSolarVolts());
  tx_payload.setLight(readLight(vcc));
  tx_payload.setSoil(readSoil(vcc));

  // Power down the soil sensor.
  digitalWrite(PIN_SENSOR_GND, LOW);

  // Disconnect the light sensor.
  // This insures that there is not a voltage higher than vcc
  // on the external ADC, as the light sensor is a voltage source.
  pinMode(PIN_SENSOR_GND, INPUT);
  
  // Build the payload buffer.
  uint8_t payload_buf[tx_payload.size()];
