io

const int poti1 = A0; // Analog input pin that the Ph probe is connected.
//const int poti2 = A1; // Analog input pin that the Ph probe is connected.

int sensorValue = 0;        // 10bit value read from the PH probe.
byte address = 4;           // 00000100, first possible address.
byte PhLo = 0;              // Lo-byte of 10 bit data.
byte PhHi = 0;              // Hi-byte of 10 bit data.

void setup() {
  Serial.begin(9600);  
}

void loop() {
  sendData(1, analogRead(poti1));
  //sendData(2, analogRead(poti2));
  //Serial.println(analogRead(poti1));
  
  delay(25);  // change value for slower data transfer.                   
}

void sendData(int address, int value) {
  PhHi = address | value>>8; // merge adddress and upper byte.
  PhLo = value;              // lower byte. 
     
  Serial.write(0);    // header byte.
  Serial.write(PhHi); // first byte. 
  Serial.write(PhLo); // second byte.
}