Declaring Digital Signal

Hi All,

I am working on a 3D printer with Generation 6 electronics board having atmega644a. The main code for Gen 6 is here:,92469
If you have a look at the code, you can see that I have initialized I2C at line 353-361

void receiveEvent(int howMany) 


void requestEvent() 

Then at line 396-401

  Wire.onReceive(receiveEvent); // register event 
  Wire.onRequest(requestEvent); // register event 

At line 456-459

#define I2CMODE 1 
#define SERIALMODE 0 

int inputMode = SERIALMODE; 

All of this is already in the Gen 6 code.
Then I connected Arduino Uno (having atmega328)with the Gen 6 board and started communicating via I2C.

#include <Wire.h> 

//i2c address of the gen 6 
int REP_RAP_ADDR = 4; 
//my address 
int CP_ADDR = 5; 

void receiveEvent(int howMany) 
  while(0 < Wire.available()) // loop through all 
    char c = Wire.receive(); // receive byte as a character 
    Serial.print(c);         // print the character        

void sendGCode(char* GCode) 

void setup() 
  Wire.onReceive(receiveEvent); // register event so that anything received on i2c is sent to the serial 

  //Test gcode, this should send the machine's X, Y and Z to home 
  sendGCode("G28 X0 Y0 Z0\n"); 

void loop() 

Now I need a digital signal from Arduino (say pin 2). I have connected a LED at pin 2. I want Gen 6 to know that there is a digital signal at pin 2 of Arduino and when Gen 6 is printing, the digital signal should be 1 and when it is not printing, it should be 0.
How to achieve this ??

What is controlling the extruder motor? Probably at some point the extruder motor is turned on or enabled, and that would be a good time to turn on the LED.

- Ryan