Pololu Uneven Microstepping - solution.

[Stub Mandrel]

16 hours ago, hdutton said:

I tried to get the Teensy3.2 micro-controller to trigger the "Open" state on the TMC2100 CFG pins, but no luck.  Setting the Teensy3.2 pin to "Input" or even "Output Open-Drain" didn't work.

Not familiar with that microcontroller, but on an AVR/Arduino you would need top set the pin as a Hi-Z input AND turn off any internal pullup to make it float. Of course this is seen as bad practice

[hdutton]

Thanks for the heads up, I assumed setting a pin to INPUT would leave pullups off.  But I was looking at the voltages on the pins in question while experimenting with this, they seemed to be floating at around 2.2 volts give or take about 0.5v (3.3v logic levels.)  I wonder if there's a built in capacitance at work on the MCU pins and that's fooling the tri-state detection on the TMC2100.  No big deal, the TMC2100 is a nice option (for OnStep users) even with this little limitation.

Howard

[hdutton]

I wanted to mention that I learned of a possible solution to the problem of full tri-state control (of the CFG pins) of the SSS TMC2100 when it's directly wired into a MCU (the Teensy3.2/Arm M4 in my tests.)

I recently was told by someone who tackled this very issue (on a different MCU) that the solution is to power the VIO pin of the SSS (where it gets it's reference voltage from) with an I/O pin of the MCU.  I had it wired into the 3.3V VRM output of the Teensy3.2 and this isn't evidently the way to go.

I haven't tried this yet so if someone has success please let us all know.

Howard