Internal ESP32 temperature value is Fahrenheit but displays unit °C

[sternegugger]

I am using ESP32-WROOM-32 with tasmota32 version 9.5.0
and like to measure the room temperature.

The Web interface shows:
"ESP32 Temperature 70.6 °C"

But my room temperature is 21.4 °C.
Calculating the displayed value 70.6 from Fahrenheit to Celsius results 21.4 °C, which is exactly my room temperature.
So I guess the internal temperature of my ESP32 is measured in Fahrenheit, but displayed with unit "°C".

In the documentation I found something like "CPU temperature".
I know the CPU temperature could be much higher than the room temperature.
But the ESP32 temperature is stable, independant of the CPU runnung time or CPU load.

Is this a bug or dependand of the used chip?
It would be nice to have this fixed. That would save me one extra temperature sensor.

[Jason2866]

It is not the room temperature. Depending on chip rev.? the shown temperature is garbage.

[sfromis]

Even if the sensor produced useful results, it would not be ambient temperature. I've seen lots of ESP32 temperature values neither making sense as Celsius nor Fahrenheit. As I see that nonsensical number as a nuisance, I'm normally disabling the ESP32 sensor function of Tasmota using SetSensor127 0 (unless I want to have the Hall Effect sensor).

Right now, on one board I'm seeing values of "48.9°C", which would be 9.9 C if read as F. I'm not sitting in such a cold room. While it in principle could make sense as a CPU temperature in C, fingering the chip (not encapsulated under a metal shield) reveals that it is not that hot either.

[bobybobybob]

The internal temperature values look quite good compared to external sensors nearby with a "constant" deviation of about 40-42 points.

[sfromis]

In other words, it looks horrible. Anyway, it may not be consistent across ESP32 devices.

[scargill]

Hi SFROMIS - I'm writing about some NOUS products right now... they have various Tasmota-based controllers - and all show the ESP32 temperature - I wonder if you know, one shows "Temperature" - the other shows "ESP Temperature"... erm, how do you control that wording - any idea? I know how to turn that off the the webUI and how to change from C to F thanks to comments above and the Tasmota docs - but why would one product Tasmota webUI include the word ESP32 and the other not?

[arendst]

Because one product apparently has an additional external temperature sensor, reporting as Temperature and the other uses the (not recommended) ESP32 internal temperature sensor, reporting as ESP32 Temperature.

[scargill]

Thanks for the quick response - so on the subject of "Temperature" as against "ESP Temperature" - so I've just been in and had a look at the nous B3T - I can't see anything in their template for configuration - to indicate any kind of sensor other than the power monitoring chipBL0939 RX... the rest is just normal relayand button stuff. 2 relays, 2 buttons and a switch as well as ledlink and serial tx... anyway I'll ask them - as I can't think of any other way to get a sensor in there. Can't see anything for the BL0939 about exposing temperature.

[scargill]

AH, it seems the BLO939 has a temperature sensor... right.. https://evelta.com/content/datasheets/359-BL0939-SOP16L.pdf