Before I continue with the grblHAL firmware configuration and compilation, I wanted to be sure that the board itself is working as designed.

So I wrote a simple application in the Arduino IDE ... "Test_Board.ino"

After uploading the simple application and starting the Serial Monitor in the Arduino IDE, the Pico application reports the following:

Controller Stepper Motors (Step +1/Step -1): X/x, Y/y, Z/z, A/a
Controller Disable Stepper Driver (Step +1/Step -1): 1 (X-Axis), 2 (Y-Axis), 3 (Z/A-Axis)
Controll Output (On/Off): C/c (CoolEn), D/d (SpnDir), E/e (SpinEn)
Read Status: S/s
Show this information: ?

By sending the mentioned character and numbers to the Pico, the related actions are fired and the result is reported back.

So in an easy way ...

• I am able to test the Stepper Motor driver and outputs, but also
• can check the inputs.

All went fine (*

(* Well I had trouble with two of the motor driver modules DRV8825. For what ever reason, they did not do their job. I replaced them and everything was fine.