controlling a stepper motor driven accessory

Controllers Smoothie
1

I’ve asked this question already in IRC, but I figured it couldn’t hurt to ask it again here in case my question there wasn’t clear.

I have an accessory driven by a stepper motor on driver #4 of my smoothie board. Currently, I have my config setup so that this accessory looks like an extruder. I’m not sure that’s the right way to set this up though.

What I’d like to achieve is the following simple thing:

  1. Command my accessory stepper to step X steps @ Y steps/sec. This action might take 15-20 min to complete.
  2. As the accessory driver spins for these 15-20 min, I’d control the XYZ motors on drivers 1,2 and 3 with some gcode.

So I guess I’m basically looking for a way for a stepper motor to run in the background. I’ve looked at the switch or spindle control modules but those don’t seem to be the right tool here.
Are there any m-codes or console commands that could allow me to do this? At first glance, maybe I could use M1910.x for this?
I’d very much like to solve this in software rather than hardware if at all possible.
If I have to write a new firmware module for this, I’d love to hear an expert opinion on how much work that might be. Would this be some simple module that would play nicely with the rest of the firmware? or would it take some major changes to make this work?

Thanks in advance for any advice!

Imported from wikidot

2

Hey.

There is definitely no way to do this with the current firmware.

Writing a module that does this shouldn’t be *too much* work ( as long as the movement speed is relatively slow, is it ? ), if you want to look into that, you can email me directly at wolf.arthur@gmail.com

Cheers.

3

Thanks Arthur,
I think I’ve had some success with getting this working after writing my post here. Here are my efforts to expand the firmware to support this:
github dot com/greyltc/Smoothieware/tree/M1910-for-extruder
(still in testing on my end).

It’s interesting to me that the stepping speed is somehow relevant here. I’d guess that’s because you’re worried about the idle time being eaten up by interrupts to support a super high stepping rate. To answer your question: I’d say my rate would be quite slow for this, maybe 500 pulses/sec max.