I'm trying to read from a Sam&Wing XW12A 12 channel touch sensor IC using I²C. The IC responds to an address read packet with 16 uninterrupted bits representing its state.
However, since I²C usually uses 8 bit bytes separated with an ACK signal, the 9th bit is lost when the controller sends an ACK bit for the first 8 bits.
My current code, using the Wire library, is below:
Wire.beginTransmission(devAddr);
Wire.requestFrom((uint8_t)devAddr, 2);
uint16_t buf;
Wire.readBytes((uint8_t *)&buf, 2);
This will return a 16 bit value, with bits 0-7 correct, then bits 9-15 shifted along with bit 8 missing.
Is there a way to prevent the controller from sending ACK bits and read the continuous 16 bits using the Wire library? And if not, is there any other better approach than just bitbanging the signal manually?
Edit: I've translated the I2C section of the datasheet below.
Edit 2: To prove that there's an issue, I've captured oscilloscope traces while bitbanging the address read header to the IC (but not sending ACKs). I've included a capture for each pad being pressed (and none pressed), you can see that pad 8 occurs on the first clock pulse after pad 7. If the IC was implementing I²C correctly, I would expect a gap of one clock pulse at this point while the IC waits for an ACK from the controller.
