Accidentally posted this in the wrong spot, so I'm re-posting it here 
Hey guys, so I figured I've lurked around on here long enough and although I've spent a bit of time poking around with the arduino, I still consider myself very green. I couldn't find this specific problem anywhere in the forum so I thought I'd post it here. I just learned not too long ago that the arduino can interface with a wii nunchuck and read the accelerometer data along with the joystick position, very cool! It saves me from having to buy one and solder it into a breakout board while trying to keep it somewhat level. Anyway, I've tried to communicate with the nunchuck using the code from windmeadow but I can't seem to get it working. I'm using the arduino mega (I had one lying around) and I have the SDA and SCL pins connected to pins 20 and 21. I upload the code, switch to the serial monitor, and all I get is "Finished Setup". So, I added a few more Serial.print lines just to see where things were stopping, and it looks like it stops communicating during nunchuck_init(), more specifically right after it sends the 0 at Wire.send(0x00) and before Wire.endTransmission(). Here's the code with the few serial.print lines I've added. Any thoughts on this? Thanks in advance!
#include <Wire.h>
#include <string.h>
#undef int
#include <stdio.h>
uint8_t outbuf[6]; // array to store arduino output
int cnt = 0;
int ledPin = 13;
void
setup ()
{
Serial.begin (19200);
Serial.print ("Finished setup\n");
Wire.begin (); // join i2c bus with address 0x52
nunchuck_init (); // send the initilization handshake
}
void
nunchuck_init ()
{
Serial.print ("Begin handshake\n");
Wire.beginTransmission (0x52); // transmit to device 0x52
Serial.print ("0x52\n");
Wire.send (0x40); // sends memory address
Serial.print ("0x40\n");
Wire.send (0x00); // sends sent a zero.
Serial.print ("0x00\n");
Wire.endTransmission (); // stop transmitting
Serial.print ("End handshake\n");
}
void
send_zero ()
{
Wire.beginTransmission (0x52); // transmit to device 0x52
Wire.send (0x00); // sends one byte
Wire.endTransmission (); // stop transmitting
}
void
loop ()
{
Wire.requestFrom (0x52, 6); // request data from nunchuck
while (Wire.available ())
{
outbuf[cnt] = nunchuk_decode_byte (Wire.receive ()); // receive byte as an integer
digitalWrite (ledPin, HIGH); // sets the LED on
cnt++;
}
// If we recieved the 6 bytes, then go print them
if (cnt >= 5)
{
print ();
}
cnt = 0;
send_zero (); // send the request for next bytes
delay (100);
}
// Print the input data we have recieved
// accel data is 10 bits long
// so we read 8 bits, then we have to add
// on the last 2 bits. That is why I
// multiply them by 2 * 2
void
print ()
{
int joy_x_axis = outbuf[0];
int joy_y_axis = outbuf[1];
int accel_x_axis = outbuf[2] * 2 * 2;
int accel_y_axis = outbuf[3] * 2 * 2;
int accel_z_axis = outbuf[4] * 2 * 2;
int z_button = 0;
int c_button = 0;
// byte outbuf[5] contains bits for z and c buttons
// it also contains the least significant bits for the accelerometer data
// so we have to check each bit of byte outbuf[5]
if ((outbuf[5] >> 0) & 1)
{
z_button = 1;
}
if ((outbuf[5] >> 1) & 1)
{
c_button = 1;
}
if ((outbuf[5] >> 2) & 1)
{
accel_x_axis += 2;
}
if ((outbuf[5] >> 3) & 1)
{
accel_x_axis += 1;
}
if ((outbuf[5] >> 4) & 1)
{
accel_y_axis += 2;
}
if ((outbuf[5] >> 5) & 1)
{
accel_y_axis += 1;
}
if ((outbuf[5] >> 6) & 1)
{
accel_z_axis += 2;
}
if ((outbuf[5] >> 7) & 1)
{
accel_z_axis += 1;
}
Serial.print (joy_x_axis, DEC);
Serial.print ("\t");
Serial.print (joy_y_axis, DEC);
Serial.print ("\t");
Serial.print (accel_x_axis, DEC);
Serial.print ("\t");
Serial.print (accel_y_axis, DEC);
Serial.print ("\t");
Serial.print (accel_z_axis, DEC);
Serial.print ("\t");
Serial.print (z_button, DEC);
Serial.print ("\t");
Serial.print (c_button, DEC);
Serial.print ("\t");
Serial.print ("\r\n");
}
// Encode data to format that most wiimote drivers except
// only needed if you use one of the regular wiimote drivers
char
nunchuk_decode_byte (char x)
{
x = (x ^ 0x17) + 0x17;
return x;
}