#include <Wire.h>
byte on = 100;
byte off = 200;

void setup() {  
pinMode(A1,INPUT);
Wire.begin();
Wire.setClock(10000) ;
}

void loop() {
if(analogRead(A1) > 500){
  Wire.beginTransmission(55);
Wire.write(on);
Wire.endTransmission();
}

delay(100);

if(analogRead(A1) < 500){
  Wire.beginTransmission(55);
Wire.write(off);
Wire.endTransmission();
}

delay(100);
}