Adding external microstepping drivers to a 2014 Printrbot Simple Metal
One qualm I have with these external TMC2130s is that they have a pretty finicky bootup procedure. They have to receive motor power first, then IO power, otherwise damage can supposedly occur. So I have the motor power broken out to a separate power supply which is switched on before the main 3d printer supply. Even then, powering on the 3d printer incurs several seconds of loud grrring and twitching from the motors connected to the TMCs before things settle down.
I was confident this was caused by one of the IO lines being noisy before the printer's microcontroller got to the point of initializing it, so I set out with an oscilloscope to find out what each line looked like during power up:
It doesn't look like these pins are causing the problem to me, no crazy noise or serial signals (Some of the gpio were also configured to be i2c display outputs). Unfortunately the documentation on TMC stepsticks seems a little hairbrained, so I guess my next stop is to take a look at the upstream datasheet from Trinamic and see if there's anything I can figure out from it.
Well I thought I had (months ago) linked this project to the makerspace wiki page where the details are, and hadn't. Whoops.
As the project title states, this is all an attempt to make my Printrbot Simple Metal quieter, namely by using Trinamic stepper drivers in StealthChop mode.
Originally I had planned to retrofit the new Printrboard G2, since I had heard it would use Trinamic drivers. Alas, when it arrived DRV8825's were installed. Oh well, I don't really care for the state of 32 bit printing software right now anyway.
So the next idea was to modify my existing Printrboard F4 to use external drivers. I know the board has some gpio pins brought out to headers, but the details of setting it all up got a little hairy. See that wiki page for details. The good news is that my modified Marlin firmware works! The bad news is that my breadboarded TMC2130's almost burned my house down, and I set the project aside.
Now I'm back to see if I can make it all work a little better and throw together some PCBs for the drivers to be seated in.