Mega + GRBL + CNC shield: Y axis works, X doesn't

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I have a Mega, running GRBL v1.1 for Mega, a Protoneer CNC shield (only X & Y axes), 2 TMC2130 step drivers, using LaserGRBL software for testing. My problem: the test motor works (i.e. jogs) when plugged into the Y step driver, but not the step X driver. What I've done:

  1. Set Vref on both step drivers correctly for the motor
  2. replaced the X driver with another TMC2130 to make sure it's not the X step driver
  3. checked connectivity between TMC2130 motor outputs and the stepper cable
  4. in GRBL, re-assigned X/Y step/dir to different pins; result Y still works, X still doesn't; inspired by this post: Arduino forum
  5. checked voltages on the X step driver: they're the same as on the Y driver (VIMOT 12V, VCC 5V, cfg pins open)
  6. right now, the X/Y limit switches are both unconnected, their pin state is the same (HIGH)

Any other suggestions how to diagnose this?

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Total votes: 0

Use an oscilloscope to make sure there is actually

a signal coming out of the Mega board to the X

step driver.  Or a logic probe would work.

 

--Mike