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Troubleshooting

Things to check if it does not work.

General

  • some USB cameras require physical unplung/plug-in AFTER the Rasberry Pi was turned on, there is no fix for this yet, see raspberrypi/linux/issues/6255 for such example

  • check /dev/shm/camera_*.stdout and /dev/shm/camera_*.stderr files for more details - if they still that 'everything is okay' then probably you have issues with permissions when running script for the second time (see below)

  • if you use feature to ping the printer then ensure printer is up and running and responds to ping, or just disable the feature (set PRINTER_ADDRESS="" or to PRINTER_ADDRESS=127.0.0.1)

  • check if the camera actually works - check cables if they are not damaged, if the cables are properly plugged, if the camera connects to the network...

  • check if the camera supports passed parameters such as resolution and codec, especially after replacing the camera - see tuning how to use v4l2-ctl to see available camera options.

  • check if any other app is not accessing the camera - especially local cameras are locked by another processes.

If another application is accessing camera then unfortunately only one app can access the camera and you must decide which app to run.

This means if you have something like Klipper/Obico/PrusaLink/motioneye/frigate (and so on) accessing the directly attached device to the Raspberry Pi then it will not work.

In such case you can try to find the process using fuser package, assuming /dev/video0 is your camera:

sudo apt install -y psmisc
fuser /dev/video0

See StackOverflow for more details.

In general you could create a loopback camera device but this is quite a lot of work to do.

  • check IP/domain names for remote camera - try that you can access camera over IP address, otherwise you have a DNS issues.

  • file permissions - check files under /dev/shm/camera* and /dev/video0

ls -la /dev/shm/camera* /dev/video*

and compare them with the current user executing the script or the user that is running docker (see below) or systemd service (see section below).

The quickest fix is just to delete files in /dev/shm/camera_* to fix only specific permission issues:

sudo systemctl stop prusa-connect-camera@env.service
sudo rm -f /dev/shm/camera_*
sudo systemctl start prusa-connect-camera@env.service

and see if the issue is resolved.

If you still have issues due to accessing /dev/video* then ensure the user is added to video group.

Docker troubleshooting

  • dockerized script - ensure you restart the pi after adding docker, check user permissions to the mounted files and devices (unfortunately this can get very messy with direct access to the devices and files on the host)

  • check IP/domain names for remote camera - ensure that you can access camera over IP address (or fully qualified domain name), because .local or .lan domains are not resolved. Another option is to reconfigure docker to use proper local DNS servers and not generic 8.8.8.8.

You can also try to run container with --add-host or extra_hosts in docker-compose.

Another option is to run container with --network="host" or network_mode: "host" in docker-compose.

Systemd troubleshooting

Get systemd logs

If the script runs locally but service is not running then you can get the logs like below, ensure to replace env with the name your camera is using:

  • stop service
sudo systemctl stop prusa-connect-camera@env.service
  • open new terminal and type:
sudo journalctl -f -u prusa-connect-camera

and keep it open

  • get back to the first terminal and write commands:
sudo systemctl start prusa-connect-camera@env.service
sleep 10
sudo systemctl stop prusa-connect-camera@env.service

  • get back to the terminal with running journalctl and see the logs and look carefully at the errors described there

  • copy the output from starting to the another starting command and paste on GitHub

Permissions issues

  • check if the user used in systemd file is the same as the one which executed test command - and you can edit systemd unit file via nano editor
sudo nano /etc/systemd/system/prusa-connect-camera@.service

and replace User=pi and Group=pi with the current user and group, then reload systemd and start service again

sudo systemctl daemon-reload
sudo systemctl start prusa-connect-camera@env.service

This way it will use your user account to access camera device and write files.

Last update: 2024-10-07 22:58:35 +0200 (UTC)