I built some PTT modified CM108 dongles for my buddy and I to use with our uv5r's and direwolf+xastir. These are connected to headless pi5's running bookworm, and vnc is the primary means of access?(through LAN). At first glance the cm108 audio and PTT appear to work as expected, however after transmitting the vnc cleint mouse will randomly stop responding. The timing is completely random... sometimes it goes out within a few seconds, sometimes after an hour or so of operation. When it happens, I observed the cursor in the direwolf terminal goes from flashing on/off steady every second, to very rapid random flashing. The PTT itself doesn't seem to misbehave when this happens... the tx remains off. However once it happens there's not getting the mouse back without a reboot.
I am 99.9% sure the modifications were done properly and should work like other known good examples found online. I didn't precisely follow any one particular guide to do the mods, rather I read up on several designs and sort came up with my own preferred assembly. Some designs I saw didn't include a COS diode, some did, some had no PTT led, which I wanted... anyhow my schematic is typical of other mods known good mods nothing special. I'm happy to provide more details/photos if anyone thinks this might be a hardware issue. I also have an oscope and the other usual lab tools on hand if I need to probe around to help find the issue.
I have been using keyboard shortcuts to reboot when this happens. After reboot (as long as I don't actually trigger the cm108 ptt) the pi5 operates perfetly for weeks without issue (fldigi, ft8, logging, gqrx, etc). Also, I can run direwolf in udp mode with gqrx for days without any problems.
I tried researching this online and keep coming up short. I'm 99.9% certain the modifications were done properly with the correct components (I have a significant amount of experience designing/building such mods). The only thing I can thing that might be causing this is some sort of mixed up HID permissions with the vnc mouse and the local hid output. Alas, I'm somewhat a greenhorn when it comes to such things in linux. Has anyone else seen a similar issue, maybe not just with cm108 or pi5, but perhaps similar issues with HID and direwolf ptt? Is there something I can do to try and fix this? I'm happy to do additional troubleshooting since I know it may be needed to reach a conclusion. Any help is much appreciated.
I just finished designing a PCB to use GPIO for ptt (gonna mill a 10 pack on my cnc). So in the end I could just forget about using the cm108 for ptt anyways. However I'd like to learn something from this, and I'm concerned this exact same issue could occur even with GPIO. If someone provides me with the key to fix my cm108 ptt problems, I'll be happy to mail them a spare RPI ptt hat as a thank you.
Thanks,
Kevin KO6BLZ
