I²C SoftMAC driver
The NXT has two different kind of sensors : analog sensors, simply outputting their reading as an analog level, and digital sensors acting as I²C slave devices that can be controlled and read from. Currently, the NXT has only one digital sensor : the ultrasonic radar. It acts as a I2C remote memory containing up to 8 measurements.
I2C communication between the NXT and the sensor
The DIGIxI0 and DIGIxI1 pins on the sensors' ports are digital I/O pins directly connected to the ARM7 processor. These two lines, using pull-up resistors on the remote device side, are used as a two-wire interface (TWI) on which the I²C communication protocol can be used to communicate with the sensor.
