Hi,
I am trying to use sleep mode with a A4988 driver and a nema 14. I am only doing full steps. Since I am using a battery and my movements are done after certain intervals, I need to enter sleep mode between every move.
for example I:
deactivate sleep, move 1 step CW, reactivate sleep, wait 3 seconds, deactivate sleep, move 1 step....
My problem is that when sleep is deactivated the shaft moves 1 step or 2 in the opposite direction before doing the 1 step I commanded.
At first I thought it was due to my motors not having enough holding torque when not powered but I tried with a high torque nema 14 and get the same result.

". A logic high allows normal operation, as well as start-up (at which time the A4988 drives the motor to the Home microstep position)."
This is from the datasheet, I understand when emerging sleep mode or powering up the motor sets to the home position, but since I am using full steps, sould i not already be at the home position ?
If you have any idea on how to help this issu it would be greatly appreciated.
Thanks

Full steps move between 4 different configurations of motor current, only one of which is the home position.

Instead of using sleep mode, I suggest you drive the Vref pin of the A4988 from a DAC or just a resistive divider fed from one or two pins of the mcu, so that you can just reduce the motor current between moves instead of using sleep mode.

Edited 1 time(s). Last edit at 07/04/2015 09:26AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for that info, it is indeed a good idea, sadly my boards are already printed, will have to use this on next version.

About that home position could I anticipate those software side, and just readjust after each move.
Could you explain me more about that, I have a hard time understanding the datasheet.