[Support]: Detector Temperature shows NaN on second TPU when multiple corals are defined.

[tfielding]

Checklist

• I have updated to the latest available Frigate version.
• I have cleared the cache of my browser.
• I have tried a different browser to see if it is related to my browser.
• I have tried reproducing the issue in incognito mode to rule out problems with any third party extensions or plugins I have installed.
• I have asked the AI at https://docs.frigate.video about my issue.

Describe the problem you are having

It seems that when you have multiple Coral TPU, the second detector always shows: NaN°C. If I change the defined order of the detectors, its always the second definition that renders the incorrect value. In other words, I have proven that both devices do actually have temperature information, it just seems like a UI bug with the display of the secondary detector value.

Steps to reproduce

1. define multiple coral TPU
2. go to systems metric page
3. view issue with detector temperature
   ...

Version

0.16.1

In which browser(s) are you experiencing the issue with?

No response

Frigate config file

detectors:
  coral_pci:
    type: edgetpu
    device: pci

  coral_usb:
    type: edgetpu
    device: usb

docker-compose file or Docker CLI command

devices:
      - /dev/bus/usb:/dev/bus/usb
      - /dev/dri/renderD128:/dev/dri/renderD128
      - /dev/apex_0:/dev/apex_0

Relevant Frigate log output

2025-09-04 10:38:22.866769471  [2025-09-04 10:38:22] frigate.detectors.plugins.edgetpu_tfl INFO    : Attempting to load TPU as pci
2025-09-04 10:38:22.868542627  [2025-09-04 10:38:22] frigate.detectors.plugins.edgetpu_tfl INFO    : TPU found
2025-09-04 10:38:22.879655340  [2025-09-04 10:38:22] frigate.detectors.plugins.edgetpu_tfl INFO    : Attempting to load TPU as usb
2025-09-04 10:38:26.009371060  [2025-09-04 10:38:26] frigate.detectors.plugins.edgetpu_tfl INFO    : TPU found

Relevant go2rtc log output

none

Operating system

Debian

Install method

Docker Compose

Network connection

Wired

Camera make and model

hikvision and reolink, 8 cameras

Screenshots of the Frigate UI's System metrics pages

with PCI defined first:

with USB defined first:

Any other information that may be helpful

No response

[inkeep-ai-assistant[bot]]

This appears to be a known limitation with temperature reporting for multiple detectors. According to the available sources, there is no way to perfectly correlate which detector is showing the temperatures when multiple detectors are configured (1). The temperature reporting system cannot accurately map temperature readings to specific detector names when building these stats (1).

Your configuration shows both PCI and USB Coral detectors properly detected:

detectors:
  coral_pci:
    type: edgetpu
    device: pci

  coral_usb:
    type: edgetpu
    device: usb

(2)

The logs confirm both TPUs are found successfully, but the temperature display issue you're experiencing with the second detector showing "NaN°C" is an edge case that isn't currently handled in the temperature correlation logic (1).

Frigate exposes device temperature metrics through the /api/metrics endpoint as frigate_device_temperature{device=""} (3), but the correlation between multiple detectors and their temperature readings remains imperfect in the UI display.

📚 Sources:

1. [Support]: Detector Temperature Reporting
2. Supported Hardware
3. Metrics

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Have another question? Just tag @inkeep.

[NickM-27]

This is not a bug, USB coral does not support temperature reporting

[tfielding]

check out my updated screenshots, when i change the order of the detector definitions, i get USB temp

[NickM-27]

No, like I said USB does not support reporting temperature. And as the AI said this is simply an issue of not being able to directly correlate which temperature belongs to which detector because they don't get reported in the same way.

While this isn't perfectly clear, this is just "how it is" when mixing a PCIe and USB based coral, there is nothing we can realistically do

[tfielding]

Understood. So its the Coral PCI temp just being rendered into the first detector. Perhaps the bug here then is to fix the UI so its not displaying NaN and something better formatted?