My solution for now if anyone is interested

if state.status == "off"
  M81
elif state.status == "busy"                                        ; state can't be idle because controller is busy running this macro
  M400                                                             ; wait for all movement to stop
  if heat.heaters[1].current < fans[1].thermostatic.lowTemperature ; check for all tool based thermostatic fans to be off
    M80
  else
    M291 R"Prohibited" P"PSU toggle is only allowed in standby or idle state! Wait for cooldown of hotend."
else
  M291 R"Prohibited" P"PSU toggle is only allowed in standby or idle state!"

So with try and error I found out that the problem has something to do with the cable that is running from the backpanel to the emergency off switch. It is a cable with 7 wires (7x1.5mm²) that are running mains voltage L and N to and from the switch (2 NC contacts) as well as the reset signal/macro trigger to and from the switch (NO contact) plus one PE line to connect the front of the frame to the mounting plate.
So either it was indeed interference from 230V mains voltage that was able to pull the 3.3V from the input pin 27k pullup to GND or it had to to with the wire cross section transitioning from 0.34mm² (from the input port) to 1.5mm² for the 7 wire cable in a terminal.

I now replaced the 7x1.5mm² cable with a 5x1.5mm² one plus one 2x0.34mm² shielded cable for just the reset signal and haven't had the described behaviour since.

@alankilian I think have my machine wired up properly, with all the metal parts being continuous with PE so the RCD would trip before you get electrocuted in case of a faulty insulation on the primary/AC side (components might get damaged but you wouldn't get hurt)
Also PE is continuous with the secondary/DC 0V so if I have a faulty insulation on the DC side of things, the PSUs would error out due to their short circuit protection.
The "mixed cable" actually was the idea of an electrical engineer (German guy with quite some experience) so I didn't think much of it...

So with try and error I found out that the problem has something to do with the cable that is running from the backpanel to the emergency off switch. It is a cable with 7 wires (7x1.5mm²) that are running mains voltage L and N to and from the switch (2 NC contacts) as well as the reset signal/macro trigger to and from the switch (NO contact) plus one PE line to connect the front of the frame to the mounting plate.
So either it was indeed interference from 230V mains voltage that was able to pull the 3.3V from the input pin 27k pullup to GND or it had to to with the wire cross section transitioning from 0.34mm² (from the input port) to 1.5mm² for the 7 wire cable in a terminal.

I now replaced the 7x1.5mm² cable with a 5x1.5mm² one plus one 2x0.34mm² shielded cable for just the reset signal and haven't had the described behaviour since.

@alankilian forgot, theres no pulldown to enable in software... So either wire up an external one (pullup or down doesn't matter in that case) which I'd like to avoid or get another NC contact for my Schlegel switch.

Thanks for the answers.
I am not sure about interference because this is a single cable that is isolated from others and this also happens when the machine is idle and nothing has changed for hours that could suddenly induce anything.
External pullup might be an option but just now I was wondering if it would help if I would configure the trigger to fire on a rising edge instead of a falling one and of course wire the switch to the IO1.5v (which is fed by 5V standby power) instead of IO1.gnd because if the IO1.in with internal pullup tends to fall below the threshold, it might be better to use a pulldown on it and trigger on the rising edge of the input.

Btw I am using a Duet 3 6HC, so using the IO5.5v instead of IO1.gnd would just be a matter of seconds (using a different pin on the plug and changing it in software) and wouldn't require additional hardware...

Update: it just happend and aborted a print midway through

Hey everyone,

I have an emergency switch with 2NC and 1NO contacts (name brand one, not some cheapo) that I use to

• cut the mains power (life and neutral) for the heated bed and the 24V PSU (5V standby power is not cut)
• trigger a macro with the NO contact connecting GND to IO1.in (at the moment the macro only consists of M112)
  this is how it is configured:

M950 J1 C"^io1.in"      ; create input 1 on pin io1.in, pullup enabled
M581 P1 T9 S0           ; trigger emergency off macro when input 1 is falling

The switch is working fine so far and does what it should do but from time to time trigger9 will randomly fire. So far it only happened when the printer was idling but I fear that it will cancel a print someday.
Wiring really isn't complicated and is completely stationary there is no movement at all, it is just
IO1.gnd - terminal(1) - emergency switch(NC) - terminal(2) - IO1.in

I have have no clue why this happens, could someone help me out here?
Thanks in advance

@dc42 thanks for the answer. I think having it in wouldn't have hurt anyway.
What about the new M17 command? Does it enable the steppers with full run current although no movement is issued or does it enable them with idle current?

I have read through this thread and the TMC5160 documentation and created a homing sequence that should do the stealthchop tuning within the homeall.g file. Maybe someone can double check if this works. Note that I only want to use stealthchop on X and Y although tuning for Z could be backpacked onto this script easily.

;homeall.g

;homing x and y in default mode of operation
G91                                                                   ; relative positioning
G1 H2 Z5 F240                                                         ; lift z 5mm relative to current position
G1 H1 X+/-(Xmax+5) Y+/-(Ymax+5) F3600                                 ; move quickly to x or y endstop and stop there
G1 H1 X+/-(Xmax+5)                                                    ; home x
G1 H1 X+/-(Ymax+5)                                                    ; home y
G1 X(Xhome+/-5) Y(Yhome+/-5)                                          ; back up 5mm
G1 H1 X+/-(Xmax+5) F360                                               ; home x slowly (second pass)
G1 H1 X+/-(Ymax+5)                                                    ; home y slowly (second pass)

;stealthchop tuning AT1
M18 X Y                                                               ; disable x and y steppers
M569 P(Xdrv) D3 V5 H5                                                 ; enable stealthchop and set tpwmthrs and thigh for X
M569 P(Ydrv) D3 V5 H5                                                 ; enable stealthchop and set tpwmthrs and thigh for Y
M915 P(Xdrv) T5                                                       ; set tcoolthrs for X [needed if stallguard is not used???]
M915 P(Ydrv) T5                                                       ; set tcoolthrs for Y [needed if stallguard is not used???]
M17 X Y                                                               ; enable x and y steppers [will this enable full run current or idle current???]
G4 P150                                                               ; pause for 150ms to satisfy AT1 condition
G92 X(Xhome) Y(Yhome)                                                 ; set home positions again after position loss due to M18
G90                                                                   ; absolute positioning

;stealthchop tuning AT2
G1 X(Xmax/2-ProbeOffsetX) Y(Yhome+/-5) F(240*beltpitch*pulleyteeth)   ; tuning move at "typical speed" that is nearly a straight line in order to move both steppers (CoreXY) significantly i.e. >400 full steps @ 60-300RPM

;homing z
G1 Y(Ymax/2-ProbeOffsetY)                                             ; move probe to the middle of the bed
G30                                                                   ; home z by probing the bed
G1 Z10 F240                                                           ; lift z again after probing

I tried to keep everything concerning positions and so on abstract, so that you have to enter your own correct home positions (or variables for that matter) and don't copy and paste a script that might damage your machine.
I have two questions though (see the end of lines 17 and 18) maybe this is something for David to answer...

My solution for now if anyone is interested

if state.status == "off"
  M81
elif state.status == "busy"                                        ; state can't be idle because controller is busy running this macro
  M400                                                             ; wait for all movement to stop
  if heat.heaters[1].current < fans[1].thermostatic.lowTemperature ; check for all tool based thermostatic fans to be off
    M80
  else
    M291 R"Prohibited" P"PSU toggle is only allowed in standby or idle state! Wait for cooldown of hotend."
else
  M291 R"Prohibited" P"PSU toggle is only allowed in standby or idle state!"

okay upon further testing I noticed that
1: Quatation marks are required as expected
2: comparing the status to a string is working but only if the status is "off"

In this example

if {state.status == "off"}
	M81
elif {state.status == "idle"}
	M80
else
	M291 R"prohibited" P"PSU toggle is only allowed in standby or idle state"

M81 will work if the printer is in off state (and then turn my PSU on resulting in the printer being now in idle state).
However if I run the macro again it will give me the message instead of running M80 to turn the PSU off again, although the printer is in idle state (checked that in the object model browser and by sending M117 {status.state} over DWC.
Checked spelling of the four letters thrice and also tried "Idle" instead of "idle"...
Am I completely blind or is there something to it that messes with the comparison of the word idle?

EDIT: found the root cause
when running the macro (no matter how short it is) the state of course changes to busy but only if the board is not only on standby power (intentionally?)
now I only need to find a way that the busy state of running the macro is not confused with an actual busy state...