Read wii nunchuck data into arduino

The nunchuck uses a proprietary connector. I just cut the end off of my nunchuck cable. The cable has 4 wires.
white - ground
red - 3.3+v
green - data
yellow - clock

Attach white to the Arduino's ground, red to 5 volt+, green to analog pin 4, yellow to analog pin 5. The nunchuck is only supposed to get 3.3+ volts. So far it has worked fine at 5 volts, but be warned. I am guessing that using the higher voltage will shorten the nunchucks lifespan.



#include
#include

#undef int
#include

uint8_t outbuf[6]; // array to store arduino output
int cnt = 0;
int ledPin = 13;

void
setup ()
{
beginSerial (19200);
Serial.print ("Finished setup\n");
Wire.begin (); // join i2c bus with address 0x52
nunchuck_init (); // send the initilization handshake
}

void
nunchuck_init ()
{
Wire.beginTransmission (0x52); // transmit to device 0x52
Wire.send (0x40); // sends memory address
Wire.send (0x00); // sends sent a zero.
Wire.endTransmission (); // stop transmitting
}

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;

)

source from http://www.windmeadow.com/node/42