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This example is for Wiring version 1.0 build 0100+. If you have a previous version, use the examples included with your software. If you see any errors or have comments, please let us know.

Reading the Nintendo nunchuck
This example demonstrates how to read a Nintendo nunchuck.

    #include <Wire.h>

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

    void setup()
    {
      Serial.begin(115200);
      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.write(0x40);   // sends memory address
      Wire.write((byte)0x00); // sends sent a zero.
      Wire.endTransmission();   // stop transmitting
    }

    void send_zero()
    {
      Wire.beginTransmission(0x52);  // transmit to device 0x52
      Wire.write((byte)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.read());  // 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 ");
      Serial.print(joy_x_axis, DEC);
      Serial.print("  ");
      Serial.print("joy_y ");
      Serial.print(joy_y_axis, DEC);
      Serial.print("\r\n");

      Serial.print("accel_x ");
      Serial.print(accel_x_axis, DEC);
      Serial.print("  ");
      Serial.print("accel_y ");
      Serial.print(accel_y_axis, DEC);
      Serial.print("  ");
      Serial.print("accel_z ");
      Serial.print(accel_z_axis, DEC);
      Serial.print("\r\n");

      Serial.print("z_button ");
      Serial.print(z_button, DEC);
      Serial.print("  ");
      Serial.print("c_button ");
      Serial.print(c_button, DEC);
      Serial.print("\r\n");

      delay(1000);
    }

    // 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;
    }