Duet3 BLTOUCH3.1 Probe deploys but doesn't trigger on Z Home

Thalios

I have a 3.1 BL touch with Duet 3 6HC (actually, 3 of them) running RRF 3.1.1

config.g related to limits:

; Endstops
M574 X1 S1 P"io1.in"                               ; configure active-high endstop for low end on X via pin io1.in
M574 Y1 S1 P"io2.in"                               ; configure active-high endstop for low end on Y via pin io2.in

; Z-Probe
M558 P9 C"io5.in" H5 R1 F120 T6000 A5 S0.02 B1     ; set Z probe type to bltouch and the dive height + speeds
M950 S0 C"io5.out"                                 ; create servo pin 0 for BLTouch
G31 X-2 Y42 Z1 P25 							   	   ; Probe position and offset

vistalert

@Thalios thank you so much. This also appears to confirm, in conjunction with advice I received from another user group, that the BLT 3.1 doesn't require the pull up.

I have a few more tests to conduct now, and will revert back soon, to see if I can get this to work.

@Thalios - be a new comer to RR and GCODE generally. Can I please confirm your machine homes to front-left corner. Did you use mechanical or optical endstops? I have mechanical end stops on order, but currently using sensorless homing.

Does the order of M558 and M950 matter?

Did you do anything with the BLT 3.1, with reference to the comments in the documentation about having the pulse width variable, in case machines do miss the probe status? Or did you just run the BLT straight out the box.

One final question...so it's implicit that the BL touch is using PWM communication, so I am assuming the comms from the BLT back to the D3 is also PWM. It's not the case that the BLT is simply pulling io.in to HI state, is this understanding correct?

Thalios

I'm not 100% sure about the M558 vs M950 order, but that's how i have it set because i think you need to define the probe and its pin before you can create the servo for it (M950).

As far as pulse width, I have not changed anything in there.

I do believe it is PWM, but don't take my word for it.

vistalert

@Thalios re: 558/950 - makes perfect sense. Many thanks for the clarity and input.

Phaedrux

Not exactly. The M950 command is just defining a servo. It doesn't know the servo is used by a probe. The config tool generates the M950 first and I use it that way myself and it works.

; Endstops
M574 Z1 S2                                   ; configure Z-probe endstop for low end on Z

; Z-Probe
M950 S0 C"1.io0.out"                         ; create servo pin 0 for BLTouch
M558 P9 C"^1.temp0" H5 F120 T6000            ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X0 Y0 Z2.5                          ; set Z probe trigger value, offset and trigger height
M557 X15:215 Y15:195 S20                     ; define mesh grid

Thalios

Well there you have it!

vistalert

@Thalios @Phaedrux well what is interesting to the novice is how some add the Z endstop indicating a Z probe, and others seem to have a complete absence of Z endstop config.

vistalert

By the way, where are you guys located? I'm in Perth, Australia (originally from the UK). I'm just loving the fact that you're in a time zone that makes this support process so responsive.

Thalios

I'm in Canada (Quebec). I'm not tech support, just a very enthusiastic Duet lover.

vistalert

@Thalios - agreed. I love this product, and the community makes the journey very rewarding.

Sad to say, with the new config changes and moving the connector to io5, my BL touch probe is still failing to stop the bed rising when executiong G28 Z.

Also, if I execute M401, and periodically, and briefly, tap the probe with my finger, the Z sensor in DWC always shows 0. I think I have to wait now for another BL Touch 3.1 to arrive, which may only be a couple more days.

vistalert

@Thalios - actually, may I ask if you have a brief sequence that you used to test your BLT?

For example, did you HOMEX/Y then execute G30, etc?

Thalios

When testing on a new printer, I home X, then Y, then set the bed far enough to stop it manually, and do a manual G30. If the bed stops when I manually push the bl touch in, i know it's good to go.

also, did you create a deployprobe.g and retractprobe.g?

This is my homez.g.

G91
G1 Z5 F800 H2			;_RRF3_ change S2 to H2
G90
G1 X150 Y150 F2400		; Move head to center of bed
M558 A1 F800 B0			; Set single probing at faster feed rate
G30 				    ; Do a single probe to home our Z axis
M558 A5 F120 B1			; Set multi probing at slower feed rate
G30				        ; Probe again to get a more accurate position
G1 Z2 F200

Phaedrux

@vistalert said in Duet3 BLTOUCH3.1 Probe deploys but doesn't trigger on Z Home:

@Thalios @Phaedrux well what is interesting to the novice is how some add the Z endstop indicating a Z probe, and others seem to have a complete absence of Z endstop config.

It's actually irrelevant to the probe how the z endstop is defined, because the probe is defined in M558 and G31 and called with G30. You can actually define the Z endstop as an endstop and use a z endstop in addition to the probe. G1 H1 Z-400 (home with an endstop) and G30 (home with the probe).

The reason an endstop can be defined as a probe is for using a probe device on an axis other than Z such as XY.

@vistalert said in Duet3 BLTOUCH3.1 Probe deploys but doesn't trigger on Z Home:

By the way, where are you guys located?

Canada as well. Saskatchewan.

@vistalert said in Duet3 BLTOUCH3.1 Probe deploys but doesn't trigger on Z Home:

Also, if I execute M401, and periodically, and briefly, tap the probe with my finger, the Z sensor in DWC always shows 0.

This is to be expected. Sending M401 will just deploy the servo pin. So poking the pin in this state won't cause anything to register as triggered. Only when G30 is sent does the firmware deploy the probe, move the axis, and wait for a trigger signal. Even so, the trigger pulse from the BLtouch is incredibly short and then resets when the pin is pulled back up. This combined with the web interface being unable to update fast enough means that with a BLTouch you'll rarely see the status change to 1000 even in normal operation.

vistalert

@Thalios yeah - M401 / M402 both deploy/retract.

I'll try G30. I've been clicking HOME Z in the DWC UI with the following in homez.g

; homez.g
; called to home the Z axis
;
; generated by RepRapFirmware Configuration Tool v3.1.4 on Tue Oct 20 2020 23:24:46 GMT+0800 (Australian Western Standard Time)

G91 ; relative positioning
G1 H2 Z5 F6000 ; lift Z relative to current position

G90 ; absolute positioning
G1 X250 Y250 F6000 ; go to first probe point
G30 ; home Z by probing the bed

; Uncomment the following lines to lift Z after probing
;G91 ; relative positioning
;G1 Z5 F100 ; lift Z relative to current position
;G90 ; absolute positioning

vistalert

@Phaedrux definitely looks like I should be testing with G10 not G28 Z

Phaedrux

Well G28 Z calls homez and your homez contains a move to position the probe and then does a G30 to probe the bed, so that's a fine way to test.

vistalert

@Phaedrux @Thalios - G30 same outcome, bed doesn't stop.

Thalios

actually, my deployprobe.g has:

M280 P0 S10 ; deploy BLTouch

and retract:

M280 P0 S90

vistalert

@Thalios - ditto for me too. Same commands in deploy/retract.

vistalert

@Thalios out of interest - what is your printer spec? Home design/build?

Mine is Rat Rig VCORE pro / linear rails / triple z screws.
Volcano hot end, titan aero extruder.

Interested to know for when I do finally reach bed calibration.