i2c_snoop.ino

/*
* Blog post describing the use case for this script is here :
* http://blog.ankitdaf.com/snooping-on-i2c-making-an-oled-display-work/
*
*/


#include <Wire.h>

int buff[1024];
int buff_pointer = 0;

void setup()
{
  Serial.begin(115200);           // start serial for output
  Serial.println("Ready");
  Wire.begin(0x3c);                // join i2c bus with address #4
  Wire.onReceive(receiveEvent); // register event

}

void loop()
{
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany)
{
  int j = 0;
  while (j < howMany) // loop through all but the last
  {
    int c = Wire.read(); // receive byte as a character
    Serial.print("0x");         // print the character in Hex
    Serial.print(c,HEX);         
    Serial.print(" ");
    Serial.print(c);         // print the character as ascii
        Serial.print(" ");   
    ++j;
  }
  Serial.println();
}