communicating state of a potentiometer with a second arduino board - c++

Question

I am trying to get an arduino board to read the state of a potentiometer which is connected to a master arduino board, without connecting the potentiometer to the second board with physical cables
I have tried using Wire.write and Wire.read to just transfer the one value.
The master arduino code:
#include <Wire.h>
const int dial = A0;
int reading = 0;
void setup() {
pinMode(dial, INPUT);
Wire.begin();
}
void loop() {
reading = analogRead(dial);
Wire.beginTransmission(9);
Wire.write(reading);
Wire.endTransmission();
}
The slave arduino code:
#include <Wire.h>
int reading = 0;
void setup() {
Wire.begin(9);
Serial.begin(9600);
Wire.onReceive(receiveEvent);
}
void receiveEvent(int bytes) {
reading = Wire.read();
}
void loop() {
Serial.println(reading);
}
When I read the Serial Monitor, the potentiometer or "reading" in the slave arduino limits at 255 (I don't know why) in 6 intervals (goes from 0 to 255, then drops to 0 and does that 6 times). I expect it to do the full range of the potentiometer to cap out at 1023.

Answer 1

Your ADC is 10bit and won’t fit in a byte. (Wire.write(value) sends value as a single byte). You need to send reading in 2 bytes. Here is how to make 2 bytes.
byte data1 = highByte(reading);
byte data2 = lowByte(reading);
On receiving side, reconstruct an int this way.
byte data1 = Wire.read();
byte data2 = Wire.read();
reading = int(data1) << 8 | data2;