i.MX8M Mini temperature sensor calibration

[vincentz63]

I'm using the i.MX8M Mini onboard temperature sensor to monitor the temperature of the SoC.

I'm trying to replicate some of the tests from AN12410 with my i.MX8M Mini board.

Page 52 states the that the temperature sensor must be calibrated.

"cat /sys/devices/virtual/thermal/thermal_zone0/temp: prints the temperature to the screen (the chip should be calibrated)."

How do I do that? The sensor reads 39000 a few seconds after a fresh boot, having left the SoC to cool for an hour prior. This seems high given my ambient of 22C so I am wondering if I need to calibrate it?

[AldoG · Accepted solution]

Hello,

The thermal sensor comes calibrated because the calibration is done during the manufacturing testing of the chip. The process of calibration is explained in the i.MX 8M Mini Applications Processor Reference Manual chap 5.4.5. The values used for calibration are programmed in the fuse registers for each device and so, cannot be changed.

The temperatures that you are reporting are not surprising because the temperature calculated is not from the room, but on the chip. Indeed, even at a cold start, the boot of the board requires power and resources, so the board is heating.

Best regards,
Aldo.

[vincentz63]

Hello,

Any chance of getting a reply of this one?

Thanks

JP