roboRio arbitrarily stops connecting to LifeCam, though Windows still can

[wilsonb]

We used a LifeCam HD-3000 (connected to a roboRio USB port) for a few weeks, and then seemingly out of nowhere, the roboRio was no longer able to connect to (get images from) the LifeCam. We replaced it with a new LifeCam, and it worked again for a while.

This whole sequence repeated itself three times, with three LifeCams. All the LifeCams can still be used from a PC, so we're pretty certain that we weren't just damaging our LifeCams.

Has anyone else had this problem? Any idea how to fix it? Thanks for any help.

Extra info: after a LifeCam stops being able to connect, the little blue light on the LifeCam turns on momentarily at startup and then goes off. The normal, working behavior is that the light remains on whenever the robot is on.

We are using an OpenCV VideoCapture (in Java) to connect to the camera.

[adciv]

What happens prior to you connecting the LifeCam? Are you powering up the robot? Are you restarting your code without power cycling?

[Joe Ross]

Is there anything interesting in dmesg?

Have you tried accessing the camera on the roboRIO through another method (ie WPILib's CameraServer, or LabVIEW)?

[techhelpbb]

I am not in a position to test this right now but:

When you plug in that webcam it should create a new device in /dev.
When it works take note of that device and when it doesn't see if you get a different device name in /dev or no device at all when the camera is plugged in.

Maybe a udev issue. Sometimes, for example, a default ethernet interface will move to eth1 from eth0.

[BenBernard]

By any chance are you using a USB hub or extension cable between your Lifecam and the rio? We've had very bad luck with both.

As another diagnostic point, do they show up in the roborio webdashboard?

Lastly, the blue light on the lifecam turns on briefly and then off ANY time it's plugged into the rio...it turns on and stays on only when it is active.

We had similar behavior to what you describe on our rPi, when our (open-cv based) vision code was attempting to access the camera and failing due to a bad driver setting. To rule out opencv problems, try adding basic streaming code to your robotInit to see if that works.

In addition to ports switching (mentioned by another poster above) it's also possible that you are sending bad parameters to the openCV library. We ran into trouble with exposure and brightness settings--which are sometimes "remembered" by the lifecam and sometimes are not. A poster in another thread recommended resetting the lifecam using the windows utility, but I've never tried that.

[wilsonb]

@adciv: We always tested with a power cycle in between, but it didn't change anything.

@Joe Ross and @techhelpbb those are both (trying to connect to the camera through something other than OpenCV, like WPILib; and checking /dev) good points, which I'll try as soon as I can.

@BenBernard, we're connecting the LifeCam's USB male directly to the roboRio. We haven't checked the web interface (admittedly that was quite an oversight). A while back, we ran into the problems you describe about the camera settings like exposure being reset. We resolved it by configuring the camera on startup with the v4l-ctl utility (in apt package libv4l-dev).

Oddly enough, the roboRio can see the camera now, without swapping the camera out for a new one. This suggests hardware issues to me, or possibly something with configuration of the camera (perhaps when plugging it into a laptop, the configuration reset and fixed something).