Purethermal 1 wrong temperature measurement on Linux

[Seren]

Hi everyone,

I am using my PT1 with Lepton 2.5 on a Linux machine (ubuntu 17.04, kernel 4.10.0). I checked the uvc-radiomery.py and the GetThermal app from here and here. However, the data I got was very wrong (please see the attached images. Note in the GetThermal app, the spot temp seems okay but the range was below 200).

I also tried the same code on a Mac and it worked perfectly fine. Can anyone please provide me some ideas why this happens?

Thanks a lot.

[Seren]

New finding... unplugging the USB can solve this problem, but as long as I ran opencv-capture.py (which used cv2.VideoCapture()), this problem pops up again.

[Kurt Kiefer]

Hm. Well, running cv's VideoCapture will change the v4l2 type used for data acquisition most likely to one of the non-radiometric formats, which will disable t-linear radiometric in the firmware. It should be when re-selecting the Y16 format, the firmware is supposed to re-enable t-linear radiometric on those parts, but maybe that's not working for some reason.

The reason the spot meter would work but the data would be wrong is simply that the spot meter reads its value out-of-band using the Lepton CCI interface (and not the data stream).

[Seren]

Thank you Kurt!