Stepper driver issues

Hello there!

I am currently trying to build a RepRap Mendel as part of an university project. I bought the Gen3 electronics from Makerbot, modified them according to the
standard PCB adaption instructions and got as far as testing the firmware and functionality of the boards.
Unfortunately I ran into some trouble with one of the stepper driver boards as the stepper motor doesn't respond to software input in the right way.
When I use the arrow buttons in the RepRap software's XYZ - tab the motors axis just trembles back and forth but doesn't really turn into any direction. On the other hand pressing the home button let's the motor spin back to the home location as intended.
I already tried reversing the polarity of one of the coils but without improvement. Varying the current via the potentiometer hasn't had any effect either.

Does anyone have an idea where to look for the cause of that problem? Did I already damage the chip?

PS: I can do some measurement with an oscilloscope if further input is needed.

sounds like when i have mine stepping too fast, i am still building my unit so i am not perhaps the best source but thats what it sounds like to mee

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[mike-mack.blogspot.com]

Also, last time I looked (a while ago) the default was to move in steps of 0.1mm - set the step size to 10mm and see if that moves more (apologies if you've done that).

Could be movement speed - check the firmware settings

:-)

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Reprapping blog and other rants: [renoirsrants.blogspot.com]
My Reprap: [sites.google.com]

Did you solve your problem? If so, how?