32 microsteps is likely more than the Firmata Stepper implementation to handle. The biggest challenge in creating a Stepper implementation for Firmata was that StandardFirmata uses all of the timers of an Arduino Uno (or similar). I had to compare times in a loop in order to do the stepping, which is less than desirable. It works, but it’s not precise. There may be a work-around with the new ConfigurableFirmata in that you could free up a timer for the Stepper implementation as long as no other features are enabled that would need to make use of the same timer.

For other Arduino boards that have additional timers this should not be an issue (as long as a timer-based Stepper solution is provided). I won’t likely have time to get to something like this for a while though.