The NxtMMX motor controller uses the tacho-motor class, so most of the information in the tahco-motor tutorial is applicable. However, it does not support all of the possible functions of the tacho-motor class.

Duty Cycle

The NxtMMX does not have a way to monitor the duty cycle of the motor, so reading the duty_cycle attribute will return -EOPNOTSUPP. Additionally, you cannot specify the duty cycle to use (see Speed Regulation below), so writing to duty_cycle_sp will also return -EOPNOTSUPP as well.

Battery Voltage

The NxtMMX creates a lego-sensor class device that can be used to monitor the battery voltage of the NxtMMX.

Advanced I2C Registers

There are two settings that are not changeable using the tacho-motor class, namely 0x86-Pass Count and 0x87-Tolerance. If you need to change these, you can do so by writing to the direct attribute of the lego-sensor class device.

Example - set Pass Count to 10:

$ echo -e -n "\x$(printf '%x' 10)" | dd bs=1 of=direct seek=0x86