[BUG] Starting spindle causes stepper driver to reset

[buergi]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

I'm using Marlin (LTS-2.1.2, but its the same in the bugfix branch) for a small CNC mill with the old Bigtree SKR v1.3 board. As it is only a small mill with a small spindle motor I connected the motor directly to the SKRs heat bed output.
The problem was, that very often when I starting running gcode the travelling distances were 4x larger than configured. I noticed it only happens with gcode with running spindle. After several hours of debugging I found that suddenly spinning up the spindle draw so much power that the supply voltage dropped causing the TMC 2209 stepper drivers to reset to there default configuration with 8 instead of 32 micro steps.

Bug Timeline

No response

Expected behavior

I was not sure if I should post it as a bug report or a feature request, but finally I chose to consider it a bug that the M3/4 command does directly issue a set_pwm_duty command with the target PWM instead of gradually increasing it over a time of several seconds. Certainly there are spindle motors with RPM regulation which do not require it, but at least having the option to configure a ramp-up time would be great.

Maybe it is also possible to detect such a reset of the stepper drivers somehow and either reconfigure it or stop the machine.

Actual behavior

Currently M3/4 set the spindle output directly to the target PWM.
The drop in supply voltage caused the TMC2209 to reset to its default settings and the steppers slammed into workpiece with 4x the configured movement speed.

Steps to Reproduce

I reduced the gcode to

  M3 S255
  G0 X10 Y10 Z10

whereas something like this works

  M3 S150
  G4 S1
  M3 S200
  G4 S1
  M3 S255
  G0 X10 Y10 Z10

Version of Marlin Firmware

LTS-2.1.2

Printer model

Similar as https://www.thingiverse.com/thing:4251212

Electronics

Bigtree SKR v1.3

LCD/Controller

RAMPS 1.4 LCD12864

Other add-ons

No response

Bed Leveling

None

Your Slicer

None

Host Software

None

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

conf.zip