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Troubleshooting Guide

This page covers common issues encountered when setting up grblHAL.

1. Connection Issues​

"No Port Found"​

  • Driver Missing: Ensure you have installed the CH340, CP2102, or STM32 VCP driver for your board.
  • Cable: Try a different USB cable. Many are "charge only."
  • Permissions: (Linux/Mac) Ensure your user is in the dialout or tty group.

"Garbage Characters"​

  • Baud Rate: Ensure your sender is set to match the firmware.
    • Standard Grbl: 115200
    • Native USB (STM32/RP2040): Any baud rate works, but some senders default to 115200.

2. Motion Issues​

Motors Buzz but Don't Move​

  • Wiring: Check motor coil pairs. Verify continuity.
  • Acceleration: Your $120-$122 might be too high. Lower it drastically (e.g., 50) and re-test.
  • Current: Adjust the potentiometer on your stepper driver.

Axis Moves Wrong Direction​

Dimensions are Wrong​

3. Homing Failures​

Alarm 9 (Homing Fail)​

  • Switch didn't trigger: The axis moved the max distance ($130 * 1.5) without hitting a switch.
    • Check wiring.
    • Check switch functionality with ? status report (pins should correspond to Pn:XYZ).
  • Switch triggered immediately: The switch is wired Normally Closed (NC) but configured as Normally Open (NO) in $5, or vice versa.

Axis Moves Away from Switch​

  • Invert homing direction using $23.

4. Common Alarms​

AlarmMeaningLikely CauseFix
Alarm 1Hard LimitA limit switch was hit during motion.Jog away. Check for electrical noise ($21).
Alarm 2Soft LimitCommand exceeded max travel ($130-$132).Check G-code coordinates. Home the machine.
Alarm 8Homing FailHoming switch was not cleared.Switch stuck or noise.
Alarm 9Homing FailHoming switch was not found.Switch wiring, or $23 direction wrong.

5. Spindle / Laser Issues​

Laser Won't Turn Off​

  • Check $32 (Laser Mode).
  • Ensure you are using M4 (Dynamic Power) for engraving.
  • Check if $31 (Min Spindle Speed) is 0.

Need more help? Check the GitHub Issues or join the community Discord.

6. Electromagnetic Interference (EMI)​

EMI is a common cause of unexplainable random issues, usually triggered by high-power devices like spindles, VFDs, or plasma cutters.

Symptoms​

  • USB Disconnections: The controller disconnects from the PC when the spindle starts or under load.
  • False Hard Limits: "Alarm 1" triggers randomly even when the machine is nowhere near a switch.
  • Corrupted Data: Strange characters in the console or the machine making erratic moves.
  • Frozen Probing: Probes trigger falsely or fail to trigger.

Mitigation Steps​

  1. Cable Separation:

    • Keep low-voltage signals (USB, Limit Switches, Probe) FAR AWAY from high-voltage power cables (Spindle, Stepper Motors, VFD).
    • Do NOT run limit switch wires inside the same drag chain or conduit as your spindle power cable.
    • If cables must cross, cross them at 90 degrees.

  2. Shielding:

    • Use shielded cables for all signal wiring (limits, probe) and VFD/Spindle power.
    • Ground the shield at the controller end ONLY (to avoid ground loops). The other end should be cut flush and insulated.

  3. Ferrite Cores:

    • Snap-on ferrite beads can suppress high-frequency noise.
    • Place them on: USB cables (both ends), Limit switch wires (near controller), Spindle power lines (near VFD).

  4. Usb Cable:

    • Use a high-quality, shielded USB cable with built-in ferrite chokes.
    • Keep it as short as possible.

  5. Grounding:

    • Ensure your machine frame, spindle body, and VFD are properly earthed to a central star-ground point.
    • Vacuum Hoses: Dust collection generates massive static. Run a bare copper wire inside the hose and ground it to dissipate static charge.