Can any Stepper Gurus help with DRV8825 problem?

[Stub Mandrel]

I'm trying to program an Arduino Uno to operate an euqatorial platform.

I'm using a DRV8825 for the first time as the 32-microstep resolution will be helpful.

Try what I can, the stepper will ONLY rotate in one direction. I have got it stepping once per millisecond on the STP pin, but whether I have the DIR pin high or low (I've checked with a voltmeter, it's either 0.00V or 4.76V) it resolutely steps in the same direction.

I can't figure this out, even a mis-wired stepper shouldn't do this - you can reverse a stepper by wiring a coil backwards but not make it unidirectional, as far as I know?

[teoria_del_big_bang]

I am no guru but if I can think of a reason I will let you know.

What is the motor it is driving?

Are you using the microsteping now or full step? Maybe start with fullstep to check the direction works ???

Steve

Edited June 27, 2020 by teoria_del_big_bang

[Stub Mandrel]

Standard NEMA 17,  200 steps.

Current limit set to about 280mA, everything works as expected.

All I can think of is that the DIR input of the stepper board is fried. That could explain why it isn't reading the full 5.0V I get with teh board disconnected.

Hmm... the DIR pin reads 300R to GND, while the STP pin is MUCH higher, with the UNO disconnected.

I'll try another board./

.... Yes, just swapped the stepper board for another one and it works.

 

Sorry if I wasted your time, but sometimes explaining a problem to someone else is the best way to solve it!

[teoria_del_big_bang]

Glad you have got one to work at least.

[Stub Mandrel]

Well I'm happy to have worked out a way of spotting the fault, rather than just swapping the board and never figuring it out. Now the hard part - the program!