External Trigger Error in RRF 3.5 and Later

[Bipotronic]

Hi all,

I'm experiencing strange issues with the external trigger. The trigger is configured with the following command: M581 T3 P1 S0 R0 in the config.g. The pin is configured using M950 J1 C"!1.io1.in" on a Duet3 Exp. 3HC. According to the configuration, I created a macro in the system file folder named trigger3.g.

trigger3.g file in the system folder contains:

echo "trigger3"

Now, when I power up the machine without homing, the trigger works as expected. If the input of Pin1 changes, the trigger is activated, and I get the following output in the console.

Trigger before homing:

So far so good!

But now it gets strange. When I home the machine, the trigger activates multiple times and doesn't shut off, regardless of whether the input at Pin1 changes or not. It’s as if the trigger is stuck in an infinite loop where it keeps getting activated.

Check the console output after the homing files are executed (pay attention to the timestamps):

The trigger activates randomly every second or two (sometimes multiple times per message) without any changes to the input of Pin1. The corresponding GPIO pin in the object model remains stable.

I've already checked my homing files for the issue but couldn't find anything unusual; it's a pretty standard homing file.

homingall.g

M98 P"/sys/homex.g"
M98 P"/sys/homez.g"

homigx.g

;  home Y-Axis 
M98 P"/sys/homey.g"	
; home X-Axis
G91               	
G1 H2 Z10 F800   	
G1 H1 X-500 F2500 	
G1 X10 F6000       	
G1 H1 X-500 F360  	
G1 H2 Z-10 F800  	
G90               	
M400

homey.g

G91              
G1 H2 Z10 F800   
G1 H1 Y-500 F2500
G1 Y10 F6000     
G1 H1 Y-500 F360 
G1 H2 Z-10 F800  
G90              
M400

homez.g

M574 Z2 S1 P"!io3.in"              
;Homing Z
G1 H1 Z600 F2000        			
G91 G1 Z-10 F2000					
G90 G1 H1 Z600 F800					
G91 G1 Z-10 F800					
G90                    										
; BL-Touch
G1 X250 Y200 F10000					
G1 Z20 F2000						
G30 								
G1 Z150 F2000 						
M400

Here’s the troubleshooting I've already done:

• Tried different RRF versions (works as expected in 3.4.6, but the problem occurs in 3.5 and later).

• Tested a different sensor input, such as the X-axis endstop, to ensure a stable signal (same incorrect behavior).

• Couldn't find any relevant notes in the changelog on GitHub.

Specs:

• Duet 3 MB6HC 3.5.2

• Duet 3 Expansion EXP3HC 3.5.2

• Duet Web Control (DWC) 3.5.2

Does anyone have any ideas about what might be causing this? From my perspective, it seems to be related to RRF.

Thanks in advance!

[dc42]

@Bipotronic most likely the wire connected to io1.in is picking up noise, most likely from nearby stepper motor wires. What is it connected to?

[Bipotronic]

@dc42 Thank you for your suggestions.

Indeed, the issue was caused by motor currents inducing some noise in the sensor cable.

I followed the procedure I described above and then simply sent an M18 command to disable the motor, and it worked fine. However, when I sent an M17 command to enable the motors again, the issue reoccurred.

I’ve since changed the wiring, and now everything works perfectly.

Thank you so much for your help!