Thanks you all, adding the timings to the M569 commands as @jay_s_uk and @PCR suggested fixed it!

As far as I am aware, it can only do G-Code since it's basically just a list of G-Code commands executed in sequence.

Two more ideas which, however, are probably still not exactly what you are looking for:

1. Use a minimal Microcontroller powered off the Duet like an Arduino or even better a Bare Microcontroller with a WiFi Shield or something like that to monitor a Level-change on some pin and send out a notification to your Pi

2. Use a Serial/UART to WiFi Bridge and read the serial data from the Duet using the Pi.

Let me know if you find some other solution to your question, I'd be very interested in hearing about it..!

@Veti thanks.

I do understand the meaning of the error; but that's what I am saying - there is no way, there is over 2mm of height difference. And before I changed the probing positions, that error never showed up..

I adjusted that very line in my config.g to this:

M671 X-49:333 Y140:140 S0.75	; define the two Z leadscrew positions (right: -49/140, left:333/140) and max correction of 0.75

But now even weirder I get the following error:

G32
Error: Some computed corrections exceed configured limit of 0.75mm: -2.095 -0.356

And even I don't exactly know the height-difference; I can absolutely guarantee there is by no means a difference of two millimeters? And why are there two values anyway?

@fcwilt good point! I used the probing-point coordinates for the leadscrews as well by mistake..

I already tried that without success unfortunately!

Seasons greetings, everyone!

Ok, so my bed.g now looks like this:

G28					; home all

G1 Z5.25				; lower bed a bit
G1 X162.85 Y174.15			; move to center point

G30 S-2					; adjust Z

G30 P0 X34.6 Y174.15 Z-99999		; probe near right Z motor leadscrew	
G30 P1 X291.1 Y174.15 Z-99999 S2	; probe near left Z motor leadscrew	

G1 X162.85 Y174.15 Z5.25		; move to center point (again)
G30 S-2					; re-adjust Z

G28 XY					; home X and Y

However, now I always get the error

G32
Error: Probe points P0 to P1 must be in clockwise order starting near minimum X and Y

Thanks for clearifying, Frederick and Phaedrux!

I really think I got confused about the different techniques there..

Ok, so what I am trying do accomplish is to have my printer automatically level the bed as far as possible.

My printer has two independent Z-motors to lift the bed, one on each side.
Homing is done using two independent Z-limit-switches (mounted close to the corresponding motor leadscrew), and both switches still allow for about 1mm of moving further up (at least physically), once they trigger.

In order to get the bed as level as possible, slightly offset to the nozzle a ir-probe is mounted and should be used for the fine-tuning, I guess.

The complete config.g of mine:

; General preferences
G90                                             ; send absolute coordinates...
M83                                             ; ...but relative extruder moves
M550 P"My 3D Printer"                           ; set printer name
M669 K1 X1:0:0 Y0:1:0 Z0:0:1                    ; set CoreXY mode

; Network
M552 S1                                         ; enable network
M586 P0 S1                                      ; enable HTTP
M586 P1 S0                                      ; disable FTP
M586 P2 S0                                      ; disable Telnet

; Drives
M569 P0 S1 R0                                   ; physical drive 0 is disabled (R0)
M569 P1 S1 R0                                   ; physical drive 1 is disabled (R0)
M569 P2 S1 R0                                   ; physical drive 2 is disabled (R0)
M569 P3 S1                                      ; physical drive 3 goes forwards (E0)
M569 P4 S0                                      ; physical drive 4 goes backwards (E1)
M569 P5 S1 R1 T5.05:5.05:0.5:0.5                ; physical drive 5 goes forwards (E2 on Expansion Header, X)
M569 P6 S1 R1 T5.05:5.05:0.5:0.5                ; physical drive 6 goes forwards (E3 on Expansion Header, Y-Left)
M569 P7 S0 R1 T5.05:5.05:0.5:0.5                ; physical drive 7 goes backwards (E4 on Expansion Header, Y-Right)
M569 P8 S1 R1 T5.05:5.05:0.5:0.5                ; physical drive 8 goes forwards (E5 on Expansion Header, Z-Left)
M569 P9 S1 R1 T5.05:5.05:0.5:0.5                ; physical drive 9 goes forwards (E6 on Expansion Header, Z-Right)
M584 X5 Y6:7 Z8:9 E3:4                          ; set drive mapping
M350 X16 Y16 Z16 E16 I0                         ; configure microstepping with interpolation
M92 X855.00 Y420.00 Z6316.00 E837.00            ; set steps per mm (X = 20T, Y = 60T, Z = M8:1.25)
M566 X600.00 Y300.00 Z50.00 E820.00             ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z1500.00 E1200.00        ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z1000.00 E250.00           ; set accelerations (mm/s^2)
M906 X800 Y800 Z800 E1000 I30                   ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                         ; Set idle timeout

; Axis Limits
M208 X0 Y0 Z0 S1                                ; set axis minima
M208 X284 Y333 Z370 S0                          ; set axis maxima

; Endstops
M574 X1 S1 P"xstop"                             ; configure active-high endstop for low end on X via pin xstop
M574 Y1 S1 P"ystop+exp.e2stop"                  ; configure active-high endstop for low end on Y via pin ystop / exp.e2stop
M574 Z1 S1 P"zstop+exp.e3stop"                  ; configure active-high endstop for low end on Z via pin zstop / exp.e3stop

; Opposite Side Limit Switches
M950 J1 C"^exp.e4stop"							; create input J1 on pin exp.e4stop
M581 P1 S0 T3 C0								; configure active-high X/Y/Z-Axis Upper Limit switch (S0 = falling edge)

; Magnetic Filament Monitor
M591 D0 P4 C"exp.e5stop" S1 A0					; configure Filament monitoring for E0 on pin exp.e5stop
M591 D1 P4 C"exp.e6stop" S1 A0					; configure Filament monitoring for E1 on pin exp.e6stop


; Z-Probe
M558 P1 C"zprobe.in+zprobe.mod" H5 F120 T3000   ; set Z probe type to modulated and the dive height + speeds
G31 P400 X21.6 Y34.15 Z1.83                     ; set Z probe trigger value, offset and trigger height
M557 X45:301 Y35:336 S30                        ; define mesh grid

; Dual Z-Motor bed levelling
M671 X34.6:291.1 Y:174.15:174.15 S0.75			; define the two Z leadscrew test-positions (right: 13/140, left:269.5/140) and max correction of 0.75

; Heaters
M308 S0 P"bedtemp" Y"thermistor" A"Heated-Bed" T100000 B4138  ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0                           ; create bed heater output on bedheat and map it to sensor 0
M307 H0 B0 S1.00                                ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0                                         ; map heated bed to heater 0
M143 H0 S145                                    ; set temperature limit for heater 0 to 145C

M308 S1 P"e0temp" Y"pt1000" A"E0-Temperature"	; configure sensor 1 as PT1000 on pin e0temp
M950 H1 C"e0heat" T1							; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00								; disable bang-bang mode for heater  and set PWM limit
M143 H1 S360									; set temperature limit for  heater 1 to 360C
M308 S2 P"e1temp" Y"pt1000" A"E1-Temperature"   ; configure sensor 2 as PT1000 on pin e1temp
M950 H2 C"e1heat" T2                            ; create nozzle heater output on e1heat and map it to sensor 2
M307 H2 B0 S1.00                                ; disable bang-bang mode for heater  and set PWM limit
M143 H2 S360									; set temperature limit for  heater 2 to 360C

; Additional Temperature Sensors 
M308 S3 P"exp.thermistor3" Y"thermistor" A"X-Motor" T100000 B4138			    ; configure sensor 3 as thermistor on pin exp.thermistor3
M308 S4 P"exp.thermistor4" Y"thermistor" A"Y-Motor (Right)" T100000 B4138		; configure sensor 4 as thermistor on pin exp.thermistor4
M308 S5 P"exp.thermistor5" Y"thermistor" A"Y-Motor (Left)" T100000 B4138		; configure sensor 5 as thermistor on pin exp.thermistor5
M308 S6 P"exp.thermistor6" Y"thermistor" A"Z-Motor (Right)" T100000 B4138		; configure sensor 6 as thermistor on pin exp.thermistor6
M308 S7 P"exp.thermistor7" Y"thermistor" A"Z-Motor (Left)" T100000 B4138		; configure sensor 7 as thermistor on pin exp.thermistor7

; Fans
M950 F0 C"fan0" Q500                            ; create fan 0 on pin fan0 and set its frequency
M106 P0 S1 H-1                                  ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500                            ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H-1                                  ; set fan 1 value. Thermostatic control is turned off

; Tools
M563 P0 S"Main Extruder" D0 H1 F0               ; define tool 0
G10 P0 X0 Y0 Z0                                 ; set tool 0 axis offsets
G10 P0 R0 S0                                    ; set initial tool 0 active and standby temperatures to 0C
M563 P1 S"Support Extruder" D1 H2 F1            ; define tool 1
G10 P1 X0 Y0 Z0                                 ; set tool 1 axis offsets
G10 P1 R0 S0                                    ; set initial tool 1 active and standby temperatures to 0C
M200 D1.75										; set filament diameter for all extruders to 1.75mm

; Miscellaneous
M575 P1 S1 B57600                               ; enable support for PanelDue
T0                                              ; select first tool

; Heater settings
M307 H0 A143.3 C694.4 D1.3 B0					; PID settings for bed heate
M307 H1 A390.2 C250.5 D11.7 B0					; settings for heater 1
M307 H2 A663.8 C218.7 D4.7 B0					; settings for heater 2

I see, thanks Frederick.

I got confused by the deprecated-message when using the Mesh bed compensation, I guess.

So the question would then rather be: "Is there a way to monitor mesh bed compensation?"

In case you cannot physically connect the Rpi to the Duet for whatever reason you could use something like this https://coptonix.com/products/lan-i2c-adapter-ms/
and send a I2C-request from the Duet to the Pi via Ethernet.

This is how I have done it:

• Connect any unused Output of the Duet with one of the GPIOs of your Pi alongside with a GND connection (optionally use a opto-coupler for the GPIO connection for power isolation).
• Use a Macro on the Duet using the M42 command to switch the pin on the Duet-side high/low.
• Watch the GPIO-pin from within your python script for change.