Hi,

I would like to discuss the posibility to build a microcontroller based stepper motor driver able to drive bipolar motors in microstepping mode.

Specs of driver :
- cost effective solution composed by a microcontroller and 2 Fet based H-Bridges
- PWM driving (not current chopping)
- start point schematic is Mariss's schematic from thread http://www.cnczone.com/forums/showth...=24699&page=54


Questions :
- How to set up the fill factor of of PWM ? Would be suitable a PID function in this case ? Usually PID function thakes as input the error (defined as difference between desired value and measured value ) and sets the drive value. In this case when desired coil current it is evaluated trough a simple comparator I think that it is not applicable. Would be necessary a very fast ADC.
- It is mandatory PID on PWM ?
- What microcontroller would be suitable for this job ? (only cost effective solution that comes to my mind is at90PWM2/3 has integrated PowerStageController - pwm with programable deadtime )


Regards,
Daniel