Reset motor's internal position

[chrisruk]

Asked about here https://forums.raspberrypi.com/viewtopic.php?p=2015482

[BeebBenjamin]

I wondered if this was possible too.

[chrisruk]

It may be possible to do this in software library, by creating an offset.

Out of interest, what would you use this feature for?

[BeebBenjamin]

My use case for this would be starting from where the motor last stopped or was last zeroed. I wouldn't want it to return to the hard zero. If it can already do that then OK. One other thing I noticed, when asking a medium angular motor to step 10 degrees for 36 times to make 360, the motor seems to under or overshoot. Would being able to reset 0 help this at all?

[chrisruk]

I'm not quite sure what you mean by 'My use case for this would be starting from where the motor last stopped or was last zeroed'. What function do you mean you'd call?

[BeebBenjamin]

I would use run_to_position() incremented, with a reset to position after a complete revolution or whenever I want, like you can with a stepper with PID like the uStepper. If this is redundant because of run_for_degrees() then there is no need for it. For my use case (a turntable), what matters is having the quoted 1 degree accuracy from the motor, which it doesn't seem to have with run_for_degrees(), but may do if the position was able to be reset.

[chrisruk]

I'll pass this on to the firmware dev, to see if they have any suggestions to increase the accuracy of run_for_degrees.