GRBL / CNC Shield V3 showed signs of life until I ran bad G-Code

I’m running GRBL 1.1f on an Arduino Uno with CNC Shield V3.00. After trying several flavors of Universal GCode Sender (latest versions available) I was able to get a stepper motor spinning (x-axis) with the manual machine control buttons in UGS. I then sent a gcode file that included “G17 G64 P0.001 M3 S3000” which isn’t valid and predictably caused an error message. No other drama occurred, nothing got hot and the usb serial interface stayed connected to the Arduino.

Now I can’t get any kind of output from the stepper motor. I reloaded GRBL 1.1 on the Arduino and tried to manually control the motor through UGS like I did before and the motor won’t do anything. Assuming that I may have damaged the x-axis output, driver, or motor, I connected a new stepper motor and driver to the Y axis of the CNC shield and again, nothing. The Arduino seems to communicate fine but I can’t get it to make the stepper motors do anything.

Is the output of the Arduino just disabled or did I somehow toast the thing with bad G-Code? Any help would be greatly appreciated.

have you completely cut power to the machine? (that includes disconnecting the usb, which powers the Uno)

Yes, I unplugged the USB cord and disconnected the 12V power supply that drives the steppers. It sat overnight disconnected and I tried it again this morning with no luck.

Odd. Are you familiar with connecting to COM ports?

I wouldn’t call myself an expert but I’m somewhat familiar. Using Com3 at 115200 baud I can connect using Arduino IDE and Universal G-Code Sender with no obvious communication issues. I can get it to send the Grbl version info, list of current settings or whatever I ask. I forget what extra messages come back when I enable verbose mode but they didn’t appear to indicate errors or problems.

Well… After much searching it would appear the CNC Shield V3.0 is not compatible with Grbl versions later than 0.8. So a big DUH on my part it appears.

In GRBL 0.9 and later, the pin configurations have changed.

From Chamnit the author of GRBL for arduino
“Pins 11 and 12 swapped in v0.9 and after. This is to access the PWM hardware on pin 11 for spindle speed and zlimit is now pin 12. See the pin diagram in the wiki.”

You can use the board but have to make changes to the connections.
If you know programming, you can make the changes in the GRBL code.

Wow! I’m glad you found it! That would have stumped me.

This adventure keeps getting better and better. It turns out the fuse on the CNC Shield V3 board was blown. After jumpering that, motor functionality returned. For a reason yet to be determined, in one instance I noticed that jogging just the X axis stepper pulled 2 - 3 amps from the 12V power supply. That’s waaay too high and the driver got very warm very quickly. It was like the driver sent full voltage to the stepper with no current limiting. I can’t seem to reproduce it as I’m able to repeatedly jog both X and Y steppers at varying speeds with no drama.

Thanks HalfNormal. Even though I’m not using a Z axis at the moment, that’s still really helpful information.