I have built myself a cnc machine, using the Arduino uno with the cnc v3 hat.
It uses 2x y motors, 1x and 1x z motor with end stops and wired emergency stop switch.
It works well in all respects, but i cannot get it to operate the z height probe. I have tested it with several programs and none seem to "see" the status of the probe change. the wires are connected to the SCL and GND connectors on the top right socket of the cnc v3.
The Uno runs GRBL 0.9f with the modded line for the z height stop - which also works well.
I have searched all over the internet to try and find if it needs extra code in the GRBL build? But am not making any progress.
I would appreciate any help in this respect as I have rather limited knowledge of Arduino.
I have not yet tried newer GRBL builds as i do not want to potentially break my machine, that is otherwise pretty well dialed in.
That's the board I'm using. Look at the white strip of connectors, near the blue-yellow ones! There You have pins for the probes. Try and use them instead, for failing end switch.
I can't tell for sure but I think (?) Grbl 0.9 and Grbl 1.1 might be using different pins, for some signals. If this is the reason or not, I can't tell.
One good, knowing, helper, maybe @groundFungus, once sent a pin mapping of this shield. I have it printed on papper somewhere. Maybe gF will be notified by this posting.....
To use the probe, connect the probe to the SCL pin on the CNC shield (Uno pin A5). I sometimes just clip a lead onto the tool that I am going to be using from the SCL pin on the CNC shield. Test the setup first by issuing a G38.2 Z-25 F100 and touch the probe with a grounded wire. The Z stepper should stop on contact.
The command contains the axis to be probed and the speed.
For example, G38.2 Z-25 F100
G38.2 is a probe command which means, seek until the probe circuit is closed (Arduino ground to
pin A5). Z-25 means drop the Z axis down a maximum of 25mm (metric in this case). Of course, this
travel should be interrupted by probe contacting the plate surface. F100 is the probe travel speed.
You may want to slow yours down, but 100 works fine.
All of the pins on the black header opposite the limit switch connections go to ground and there is a ground right near the SCL pin. The pins in the green boxes go to ground.
Does that mean that the designated motor does not even move when the G38 is issued? Or does the motor move but will not stop when the probe (connection to SCL pin) is grounded?
I have tried the probe command in inventables easel (I usually use this program for drawing and cutting projects).
I have also tried jscnc which I used when I built the machine and had little access to anything else, as vectric is way to expensive for a hobbyist like me).
I recon one can send an online command in jscnc as well as it allows something like command prompt in windows that one can send direct commands like Ubiversal gcode sender ( which I have not yet been able to successfully install).
I asked about the ground as I was wondering if a dry joint on the ground pin could cause the issue, as I have looked at the soldering on these boards, and some look pretty weak.
See 
