Checking the trigger height ; can't do step 8

EricE555

I am trying to follow https://duet3d.dozuki.com/Wiki/Using_mesh_bed_compensation instructions for finding the trigger height of my probe (BLTouch). On step 8 it says to
"Send G30 S-1 to probe the bed without resetting the Z=0 position" but when I do that, it fails with "insufficient axis homed". If I home the axis before I do it, I am no longer where I want to probe the bed AND it runs a G30 which resets my Z=0.
What do I need to do to find my trigger height?

jay_s_uk

@EricE555 if you follow the steps, you shouldn't be unhoming the axis

i like using this macro to measure the trigger height

;Calibrate BL Touch trigger height
; When we get variables we can define one here
; Uncomment when ready to use
; var RunningTotal=0
; var average=0
  
; If the printer hasn't been homed, home it
if !move.axes[0].homed || !move.axes[1].homed || !move.axes[2].homed
  G28
  
M564 S0 H0 ; Allow movement beyond limits
 
if move.axes[2].machinePosition < 6 ; make sure we have probe clearance
	G1 Z6
M280 P0 S160 I1 ; reset BL Touch
G4 S0.5
M98 P"0:/sys/retractprobe.g" ; Ensure probe is retracted & reset
G4 S0.5
M290 R0 S0 ; clear any baby stepping
M561 ; clear any bed transform
; Jog head to position
M291 P"Jog nozzle to touch bed" R"Set nozzle to zero" S3 Z1
G92 Z0
M291 P"Press OK to begin" R"Ready?" S3; 
; carry out 10 probes
while iterations <= 9
	G1 Z6
	M400
	if sensors.probes[0].value[0]=1000 ; if probe is in error state
		echo "Probe in error state- resetting"
		M280 P0 S160 I1 ; reset BL Touch
		G4 S0.5
		M98 P"0:/sys/retractprobe.g" ; Ensure probe is retracted & reset
		G4 S0.5
	G30 S-1
	M400
	; Uncomment when variables allowed
	; RunningTotal=RunningTotal + move.axes[2].machinePosition
	;average=RunningTotal/(iterations+1)
	G4 S0.5
 
; Until variables come use this
M291 P"Check console for results and enter average value in G31 Z parameter of config.g"  R"Finished" S3 
 
;When variables come uncomment this
;G31 Z{average}
;M291 P"Trigger height set to : " ^ sensors.probes[0].triggerHeight ^ " Press OK to save to config, cancel to use until restart" R"Finished" S2 
;M500
 
 
M564 S0 H1 ; Reset limits	                                                            ; Home Z

EricE555

Thank you for your prompt reply. I tried your script.
When I run it I get 10 instances of "Insufficient Axes homed for bed probing" and then M292 -> Bad command: 0

EricE555

After figuring out what I did wrong, I was able to run this script.
I had changed M84 (idle timeout) to 10 seconds because the motors make a little noise. Once I put that back to something reasonable, I had the necessary time to adjust nozzle to the bed height and then continue the script without the errors.
Now we'll see if I can make use of this to have a good offset for the nozzle when printing.