Keep going! There was so much I didn’t know how to do when I got started. It is still that way! Sorry I can’t help more with your Python code. I do not have experience with threading. Hopefully someone else will be able to help.
Adafruit has very good examples concerning treading. Because I have two 2348 motorhats, I can command two steppermotor simultaneously. Is that good idea, I am practising at the moment.
My concern at the momen, is to get good snapshots and control the movements so, that picture is on right place at right time. I am trying to learn from Alexamder, he has a lot to shear.
On way to get more precison, may be to use Roi, to move film, but that is a new era for me.
I have used microsteps, but it does not seem to bee very accurate, and now I intend to practise Interleaved Steps ??
The approach that worked for me was finding a way to detect sprocket holes. You can use a photodiode (also called a photo-interrupter or other names) or something similar to do this. In my experience, one that detects reflective material was more reliable than one that only relied on light. That is because some films have a clear base and the light is not blocked sufficiently to register with the sensor.
In the first version of Kinograph, I use bumps on a sprocket that line up with the sprocket holes. These bumps hit a roller switch, and that is what triggers the camera. You can see that in the videos about Kinograph and the roller is available as a download on the website.