M280: Probe already triggered at start of probing move BLTouch

magnets99

Hi, i have been given a printer which is awesome, but it was on a very old firmware.
I've got everything on 3.5.4 (wifi 2.2.0) but i had to rebuild the sd card from scratch.
I havn't touched the cabling and i printed a benchy which was acceptable before i changed anything.
It has a bltouch which i observed working.
Now in the new config when i try to home z i get the error

G30
Error: M280: Probe already triggered at start of probing move

sending g31 gets me

G31
Z probe 0: current reading 1000, threshold 500, trigger height 2.200, offsets X-19.7 Y-8.4

The original config.g had this as the bltouch section

; Z-Probe
M574 Z1 S2                                                                   ; Set endstops controlled by probe
M307 H7 A-1 C-1 D-1                                                          ; Disable heater on PWM channel for BLTouch
M558 P9 H5 F120 T6000                                                        ; Set Z probe type to bltouch and the dive height + speeds
G31 P500 X-19.7 Y-8.4 Z2.2                                                        ; Set Z probe trigger value, offset and trigger height
M557 X20:190 Y15:190 S60                                                     ; Define mesh grid

and this is the new one

; Probes
M558 K0 P9 C"^exp.thermistor6" H5 F120 T6000 ; configure BLTouch probe via slot #0
G31 P500 X-19.7 Y-8.4 Z2.2 ; set Z probe trigger value, offset and trigger height
M950 S0 C"exp.heater7" ; create servo #0 for BLtouch

I haven't changed the wiring, i'm using Pin 31 HEATER7 on the expansion slot
The file for deployprobe0.g says

; deployprobe0.g
; called to deploy a physical Z probe
;
; generated by RepRapFirmware Configuration Tool v3.5.8 on Sun Dec 29 2024 16:23:01 GMT+1100 (Australian Eastern Daylight Time)

M280 P0 S10	; deploy BLTouch

M401 and M402 deploy and retract the probe successfully.
any ideas?

magnets99

ok, chatgpt helped me get the right gcode, and it helped that it turns out i have a 5 wire bltoush not a three wire one.

; Z-Probe Configuration
M950 S0 C"exp.heater7"                ; Assign Heater7 (pin 31) for BLTouch control
M558 P9 C"zprobe.in" H5 F120 T6000    ; Configure Z-Probe signal pin
G31 P500 X-19.7 Y-8.4 Z2.2            ; Set trigger value, offsets, and trigger height
M574 Z1 S2                            ; Set Z endstop controlled by the probe

the bed isn't stopping in testing, but no more errors when trying to home so i'm marking this one as solved.

magnets99

ok, i've got a bit further, i had the wrong pin which didn't help.
It should be pin 31 which is heater 7.
and it is a 3 wire harness i think. so i changed it to

; Probes
M950 S0 C"exp.heater7"                ; Assign Heater7 as the control pin for BLTouch
M558 K0 P9 C"^exp.heater7" H5 F120 T6000 ; Configure BLTouch probe, using Heater7 for signal
G31 P500 X-19.7 Y-8.4 Z2.2           ; Set trigger value, offsets, and trigger height

but now i'm getting pin exp.heater7 is not free
error invalid z probe index

i'm going to go triple check that i have a three wire system.

magnets99

ok, chatgpt helped me get the right gcode, and it helped that it turns out i have a 5 wire bltoush not a three wire one.

; Z-Probe Configuration
M950 S0 C"exp.heater7"                ; Assign Heater7 (pin 31) for BLTouch control
M558 P9 C"zprobe.in" H5 F120 T6000    ; Configure Z-Probe signal pin
G31 P500 X-19.7 Y-8.4 Z2.2            ; Set trigger value, offsets, and trigger height
M574 Z1 S2                            ; Set Z endstop controlled by the probe

the bed isn't stopping in testing, but no more errors when trying to home so i'm marking this one as solved.

Phaedrux

@magnets99 said in M280: Probe already triggered at start of probing move BLTouch:

the bed isn't stopping in testing,

The probe is only used when you send G30. It won't work on a normal G1 H1 homing move. So make sure your homing files are correct for using a probe.

magnets99

@Phaedrux
Thanks, in the end there was lots wrong, i'm not sure how i got it so wrong to start with.
original:

; Probes
M558 K0 P9 C"^exp.thermistor6" H5 F120 T6000 ; configure BLTouch probe via slot #0
G31 P500 X-19.7 Y-8.4 Z2.2 ; set Z probe trigger value, offset and trigger height
M950 S0 C"exp.heater7" ; create servo #0 for BLtouch

Final fixed one:

; Z-Probe Configuration
M950 S0 C"exp.heater7"                ; Assign Heater7 (pin 31) for BLTouch control
M558 P9 C"^zprobe.in" H5 F120 T6000    ; Configure Z-Probe signal pin
G31 P500 X-19.7 Y-8.4 Z2.2            ; Set trigger value, offsets, and trigger height
M574 Z1 S2                            ; Set Z endstop controlled by the probe

Issues were (as i went along):
assumed 3 wire config not 5 wire.
wrong pin for sensor
missing ^ (pullup) on zprobe.in

I actually found chatGPT pretty good for getting me to check stuff, it seems to know rrf 3+ pretty good.

Phaedrux

@magnets99 said in M280: Probe already triggered at start of probing move BLTouch:

I actually found chatGPT pretty good for getting me to check stuff, it seems to know rrf 3+ pretty good.

Definitely double check anything it gives you against the actual gcode dictionary. Last time I looked at it, it started to make stuff up very quickly.

magnets99

@Phaedrux
I think because i was doing basic stuff it was ok, but yes, it did get a few things wrong:

*3. Test Manual Pin Movement
Manually deploy the probe pin and push it gently into the housing while sending:

gcode
Copy code
M119
If the probe doesn't register as triggered when pushed, the issue may be:
A wiring problem.
A faulty BLTouch.
A configuration issue with the signal pin.*

Which would be good advice if i was using it as an end stop, but i wasn't.
But got me looking at the wiring...