I’m trying to connect a “chinese” nunchuck to the Wixel with the I2C library.
I know for sure that this works on the Arduino, but with the Wixel I keep getting nack on all the writings
Am I missing something?
I assume you’re talking about a Wii nunchuk (or a clone of it); do you have a datasheet for it? It might also be helpful if you could post your working Arduino code for comparison.
you right Kevin it’s a cheap wii nunchuck, and no, I don’t have a datasheet.
here you go, just the relevant Arduino code
void begin()
{
Wire.begin();
cnt = 0;
averageCounter = 0;
// instead of the common 0x40 -> 0x00 initialization, we
// use 0xF0 -> 0x55 followed by 0xFB -> 0x00.
// this lets us use 3rd party nunchucks (like cheap $4 ebay ones)
// while still letting us use official oness.
// only side effect is that we no longer need to decode bytes in _nunchuk_decode_byte
// see http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1264805255
//
Wire.beginTransmission(0x52); // device address
Wire.send(0xF0);
Wire.send(0x55);
Wire.endTransmission();
delay(1);
Wire.beginTransmission(0x52);
Wire.send(0xFB);
Wire.send(0x00);
Wire.endTransmission();
update();
}
void update() {
Wire.requestFrom (0x52, 6); // request data from nunchuck
while (Wire.available ()) {
// receive byte as an integer
status[cnt] = _nunchuk_decode_byte (Wire.receive()); //
cnt++;
}
if (cnt > 5) {
cnt = 0;
_send_zero(); // send the request for next bytes
}
void _send_zero()
{
Wire.beginTransmission (0x52); // transmit to device 0x52
Wire.send (0x00); // sends one byte
Wire.endTransmission (); // stop transmitting
}
I2C uses 7-bit slave addresses; in the case of your nunchuk, it looks like this is 1010010b (0x52). When an I2C master begins communicating with a slave, it transmits this 7-bit address followed by an 8th bit that is either 0 for writing or 1 for reading, so the master would transmit 10100100b (0xA4) to write to your nunchuk or 10100101b (0xA5) to read from it.
Arduino’s Wire.beginTransmission() function takes just the 7-bit address and automatically adds the last 0, and similarly Wire.requestFrom() takes the address and automatically adds the last 1. However, the Wixel’s I2C library only has a single function that simply writes a byte (8 bits) to the I2C interface, so when you send 0x52, you are actually sending the 8-bit sequence 01010010b. You have to add the last bit to the address yourself, so try using “i2cWByte(0xA4)” instead of “i2cWByte(0x52)” and see if that works.
