Wire digital controlled z-probe to z-probe header?

dc42

See https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Homing_Z.

dragonn

Hmmm ok, G30 turns now the Z_MOD but only if the endstop isn't triggered and in my solution the endstop is triggered before Z_MOD goes high. When Z_MOD goes high the pin is pushed out and the endstop goes low so it is ready to trigger. Is they anyway to ignore "Error: Z probe already triggered at start of probing move"? I hope.

dc42

Please post the gcode sequence you are using and explain what happens when.

dragonn

[[language]]
G91                ; relative positioning
G1 Z5 F200 	   ; raise head 4mm to ensure it is above the Z probe trigger height
G90 		   ; back to absolute mode
G1 X155 Y155 F2000 ; put head over the centre of the bed, or wherever you want to probe
G30 		   ; lower head, stop when probe triggered and set Z to trigger height
G92 Z2           ; set Z position to trigger height
G90;
G1 Z0 F200
G1 Z5 F200

```My homez.g. The problem is my bltouch isn't triggered only when Z_MOD is HIGH. When G30 runs it is triggered and shows an error. Now G30 works I assume this way:
1\. Check if probe isn't triggered
2\. If not pull Z_MOD pin high
3\. Probe z-height.

I need to change it behavior to this:
1\. pull Z_MOD high
2\. check if probe isn't triggered
3\. Probe z-height.

dragonn

Bump, any update on that?
I made a video, maybe it will explain it better what is happening:
https://www.dropbox.com/s/hwvtikp42t1pcfm/VID_20180325_123803.3gp?dl=0
as you can see, the first homing failed. Z_MOD isn't pulled high because the probe is already triggered. The second time i pulled the pin by hand and now the homing is working like expected - the Z_MOD is pulled high (bltouch lights up).

dc42

Does adding a delay before probing (R parameter in M558) make any difference?

dragonn

No, I have already 2s delay. It is added only when I pull the pin manual before probing.

dc42

I think you will need to connect that control wire to a pin on the expansion connector and control it using M42 commands in deployprobe.g and retractprobe.g. The problem is that RRF doesn't set the MOD pin high until the probing actually starts, which is too late for your probe. I can't change that behaviour without breaking other types of sensor.

dragonn

Hmmmm what if I would add a transistor to the Z_MIN to block the signal when Z_MOD is low? I think this should work. I don't like the idea to wiring to the expansion connector because it looks ugly :D.

dc42

You may need to add a delay to that circuit before the Z probe IN pin is allowed to go low, but I am sure that something like that could be made to work.