SolvedMarlin [BUG] TMC2209 Sensorless homing sensitivity is off
✔️Accepted Answer
@boelle Thank you for reopening it. I'm about to close it again, but I will update for the benefit of others. I spent the last couple of hours trying multiple things, and it looks like I managed to find a fix for the issue.
Apparently, lowering the homing speed to fairly low values fixes the issue. I set my HOMING_FEEDRATE_XY to (30*60)
and with that, I can set my stallguard sensitivity values at 100 and it seems to work perfectly (I haven't had a single false positive or false negative so far). Setting it to (45*60)
goes back to the behaviour I reported here, where it's either too sensitive or too insensitive without anything reasonable in-between.
So basically, @boelle was correct in saying this was a setup issue, but to my knowledge, the homing speed affecting the sensorless homing isn't documented anywhere. I'll try to add something to the docs about it.
Description
I have just configured a TMC2209 for my X axis, with UART. It seems to work alright, but setting up the sensorless homing is being a pain (I had it working with an TMC2130 earlier).
If I set the sensitivity to anything above 105 (
M914 X105
) and try to home the axis, it moves for about 1mm and then immediately stops. I'm assuming this is the stallguard triggering, since I haven't been able to get a read withM119
. As soon as I change the sensitivity to anything bellow that (M914 X104
) it just tries to home forever until I kill the machine. I have tried setting up floats for the value but it won't accept them, and I also tried switching it with another TMC2209 with exactly the same result.Steps to Reproduce
Config.zip
Using TMC2209 and these stepper motors, on the bugfix-2.0.x branch:
M914 X105
G1 X1
M914 X104
G1 X1
Expected behavior: Stallguard triggers when it hits something.
Actual behavior: Stallguard triggers too early (moving 1mm and hitting nothing) with the 105 sensitivity, and too late (dangerously so) with 104.
I'd appreciate any help debugging this, as I suspect it's something specific to my stepper motor/driver combination rather than a general issue.