#include <Wire.h>

const int buttonPin  = 10;

int buttonState      = 0;
int lastButtonState  = 1;

void setup() {
 Wire.begin();
 pinMode(buttonPin, INPUT);
}

void loop() {
 buttonState = digitalRead(buttonPin);
   if (buttonState != lastButtonState) {
     if (buttonState == 1) {
         Wire.beginTransmission(2);
         Wire.write('p');
         Wire.endTransmission(2);
     }
     lastButtonState = buttonState;
   }
 delay(20);
}