Unsolved Duet 3 issue with endstops and sbc communication

[tristanryerparke]

When setting up a duet 3 (rpi 4) with 24v npn normally closed proximity sensors, I am running into some issues. I set up this proximity sensor like so:
Signal Wire --> io0.in
Ground --> GND (io0 header)
Vin(6-36v) --> 24v (psu)
Knowing that the duet 3 ioX.in pins can take 30v input, I set up a proximity sensor while the duet was turned on. The sensor worked and showed up turning yes/no in dwc when triggered. This whole time, the DIAG led was blinking slowly bright red. The sensor also continued to work when restarting the duet (after changing config.g).

THEN, I turned off the duet and turned back on, waited for pi to boot and tried to connect. I got the error "Failed to Connect to duet3.local" with subtext "DCS is not started". The DIAG led is dimly lit and not blinking.
Browsing the forum I found this command to check connection:

sudo journalctl -u duetcontrolserver -e

I am able to ssh into the pi so I ran it with this output:

Aug 22 19:31:48 duet3 systemd[1]: duetcontrolserver.service: Succeeded.
Aug 22 19:31:53 duet3 systemd[1]: duetcontrolserver.service: Service RestartSec=5s expired, scheduling restart.
Aug 22 19:31:53 duet3 systemd[1]: duetcontrolserver.service: Scheduled restart job, restart counter is at 142.
Aug 22 19:31:53 duet3 systemd[1]: Stopped Duet Control Server.
Aug 22 19:31:53 duet3 systemd[1]: Started Duet Control Server.
Aug 22 19:31:53 duet3 DuetControlServer[2512]: Duet Control Server v3.1.1
Aug 22 19:31:53 duet3 DuetControlServer[2512]: Written by Christian Hammacher for Duet3D
Aug 22 19:31:53 duet3 DuetControlServer[2512]: Licensed under the terms of the GNU Public License Version 3
Aug 22 19:31:54 duet3 DuetControlServer[2512]: [info] Settings loaded
Aug 22 19:31:54 duet3 DuetControlServer[2512]: [info] Environment initialized
Aug 22 19:31:54 duet3 DuetControlServer[2512]: [fatal] Could not connect to Duet (Board is not available (no header))
Aug 22 19:31:54 duet3 systemd[1]: duetcontrolserver.service: Succeeded.
Aug 22 19:31:59 duet3 systemd[1]: duetcontrolserver.service: Service RestartSec=5s expired, scheduling restart.
Aug 22 19:31:59 duet3 systemd[1]: duetcontrolserver.service: Scheduled restart job, restart counter is at 143.
Aug 22 19:31:59 duet3 systemd[1]: Stopped Duet Control Server.
Aug 22 19:31:59 duet3 systemd[1]: Started Duet Control Server.
Aug 22 19:32:00 duet3 DuetControlServer[2564]: Duet Control Server v3.1.1
Aug 22 19:32:00 duet3 DuetControlServer[2564]: Written by Christian Hammacher for Duet3D
Aug 22 19:32:00 duet3 DuetControlServer[2564]: Licensed under the terms of the GNU Public License Version 3
Aug 22 19:32:00 duet3 DuetControlServer[2564]: [info] Settings loaded
Aug 22 19:32:00 duet3 DuetControlServer[2564]: [info] Environment initialized
Aug 22 19:32:00 duet3 DuetControlServer[2564]: [fatal] Could not connect to Duet (Board is not available (no header))
Aug 22 19:32:00 duet3 systemd[1]: duetcontrolserver.service: Succeeded.

I unplugged the proximity sensor at io0.in and cycled the power on the duet/psu, and everything worked as normal, no error messages, moved steppers ran macros etc. Sensor works when plugged back in, but turning off/on psu keeps duet from connecting to pi again and I get the same message.

Tried this on 3.1.1 as well as 3.2beta2 and got the same issue.
On 3.2beta2 I got a slightly different error message:
"Failed to connect to duet3.local" "Failed to connect to duet, please check your connection(dcs is not started)"
Also on 3.2beta2 the endstop works (switch can be observed in OM) if you plug it in after the duet has booted.
Is there some issue with these NPN switches preventing the duet from booting? This seems like a serious bug to me for those of us using such switches.
Best,
T

[dc42]

That's an interesting fault. Does it work if you connect the probe to a different IO connector? IO_0 may be a little special because that's where a PanelDue would be connected.