nunchuk_control.ino

#include <Wire.h>

static uint8_t nunchuck_buf[6];   // array to store nunchuck data,

void setup(){
  Serial.begin(115200);

  nunchuck_setpowerpins(); // use analog pins 2&3 as fake gnd & pwr
  nunchuck_init(); // send the initilization handshake
}

void loop(){
  nunchuck_get_data();

  // map nunchuk data to a servo data point
  int x_axis = map(nunchuck_buf[0], 23, 222, 180, 0);
  int y_axis = map(nunchuck_buf[1], 32, 231, 0, 180);

  nunchuck_print_data();

}

static void nunchuck_setpowerpins(){
#define pwrpin PORTC3
#define gndpin PORTC2
  DDRC |= _BV(pwrpin) | _BV(gndpin);
  PORTC &= ~ _BV(gndpin);
  PORTC |=  _BV(pwrpin);
  delay(100);  // wait for things to stabilize
}

// initialize the I2C system, join the I2C bus,
// and tell the nunchuck we're talking to it
void nunchuck_init(){
  Wire.begin();                      // join i2c bus as master
  Wire.beginTransmission(0x52);     // transmit to device 0x52
  Wire.write(0x40);            // sends memory address
  Wire.write(0x00);            // sends sent a zero.
  Wire.endTransmission();     // stop transmitting
}

// Send a request for data to the nunchuck
// was "send_zero()"
void nunchuck_send_request(){
  Wire.beginTransmission(0x52);     // transmit to device 0x52
  Wire.write(0x00);            // sends one byte
  Wire.endTransmission();     // stop transmitting
}

// Receive data back from the nunchuck,
int nunchuck_get_data(){
  int cnt = 0;
  Wire.requestFrom (0x52, 6);     // request data from nunchuck
  while (Wire.available ()) {
    // receive byte as an integer
    nunchuck_buf[cnt] = nunchuk_decode_byte(Wire.read());
    cnt++;
  }
  nunchuck_send_request();  // send request for next data payload
  // If we recieved the 6 bytes, then go print them
  if (cnt >= 5) {
    return 1;   // success
  }
  return 0; //failure
}

// 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 nunchuck_print_data(){
  static int i = 0;
  int joy_x_axis = nunchuck_buf[0];
  int joy_y_axis = nunchuck_buf[1];

  int z_button = 1;
  int c_button = 1;

  // byte nunchuck_buf[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 ((nunchuck_buf[5] >> 0) & 1)
    z_button = 0;
  if ((nunchuck_buf[5] >> 1) & 1)
    c_button = 0;

  Serial.print("joy:");
  Serial.print(joy_x_axis, DEC);
  Serial.print(",");
  Serial.print(joy_y_axis, DEC);
  Serial.print("  \t");
  Serial.print("c:");
  Serial.print(c_button, DEC);
  Serial.print("  \t");
  Serial.print("z:");
  Serial.print(z_button, DEC);

  Serial.print("\r\n");
  i++;
}

// 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;
}