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1.13.0/1.14.0 - Simple JeVois-For-FRC module freezes camera quickly:-(

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just started playing the A33, but so far, I run into trouble quickly, It's totally possible, that I do something stupid, but since the camera is working as expected for different periods after start, I'm not so sure, what's going on:-(

I'm trying to use the module from https://github.com/asid61/JeVois-For-FRC (one minor adoption for OpenCV 4) and the camera works for a bit, but eventually freezes:-( The period ranges from < 10 seconds to > 20 minutes:-(

Once the camera freezes, guvcview just reports

V4L2_CORE: (VIDIOC_DQBUF) Unable to dequeue buffer: No such device
V4L2_CORE: (VIDIOC_DQBUF) Unable to dequeue buffer: No such device
V4L2_CORE: (VIDIOC_DQBUF) Unable to dequeue buffer: No such device

and the ArduinoIDE console does not react at all any more:-(

I tried to capture my screen (for a rather shore run with 1.14.0): https://www.bytesalad.org/~marco/t2-2019-09-14_10.46.35.mp4

Any idea?


-- Marco

asked Sep 14, 2019 in Programmer Questions by mw46d (120 points)

1 Answer

0 votes
That error means JeVois was disconnected somehow. It could either be a crash, or a mechanical issue at the connector. USB connectors are not designed for mechanical stress, so you should use strain relief for the connector and cable when mounting on a robot. Have a look at this one, it is super nice:


See how there is a clamp for the USB connector behind the camera. You secure the cable to the mount using a zip tie once the cable and camera are mounted.

On the software side, we have cameras running 24 hours a day for months here with no problem... In the JeVois inventor console or your Arduino console, try things like "shell free" and monitor the amount of free RAM over time. If it is going down (beyond small fluctuations), then maybe your code is leaking memory or crashing somehow. To investigate that, try to run our TensorFlowEasy code on your camera. This one is pretty brutal, gets near 400% of CPU usage. If that one is stable, then the hardware is ok. If that one crashes and you are not moving the camera around, maybe the hardware has a problem.

that video of a very short run also suggests that maybe you have a power issue. Make sure you use a Y cable, and that your computer can indeed source 500mA each port. Small boards like the raspberry pi typically cannot, since they are powered from a single USB port themselves.Have a look here for tips:

answered Sep 17, 2019 by JeVois (46,200 points)
Thanks for your ideas;-)
* It's probably not a mechanical issue (short of a cold solder joint or similar). The camera (and connected laptop) is not moving right now.
* The camera is connected to an USB3 port (I tried all four on the laptop at different times), that should give enough power. I also tried with an additional 2.4A power on the Y-cable, same issue:-(
* So, I'll try to look closer at the software side of things.
-- Marco

It seems to be the original Y-cable and/or the USB connector:-( The TensorFlowEasy did die as quickly as the other module with the original Y-cable, even with the extra power.
Now I replaced the cable with a Y-cable from a DVD player and the TensorFlowEasy is running fine for about two hours. It's currently powered by the laptop USB3 port alone;-)
I'm printing the mount as well and once that's done, I'll try the original cable again.
oh, thanks for letting us know. Please email us your order number to jevoisinc@gmail.com and we will send you a refund for the USB cable. Indeed we have had a few bad ones. We have changed supplier since then.