STEVAL-SMARTAG humidity sensor readout problem

[Peter S.]

I have flashed the example code from the function pack on 2 STEVAL-SMARTAG modules using a Nucleo STLink. After flashing, I get very different (incorrect) values from the humidity sensor (31% whereas the original sensor, as purchased, read the correct value of 48%). The temperature sensor is still fine.

The code I used is:

en.fp-sns-smartag1\STM32CubeFunctionPack_SMARTAG1_V2.0.0\Projects\STEVAL-SMARTAG1\Examples\SmarTag1\MDK-ARM\Project.uvprojx

I use an iPhone to read the sensor via NFC. Does anyone know what could be the problem?

Is the code that is supplied on the SMARTAG module different from the example code?

[Eleon BORLINI]

HI Peter, is the humidity value changing from 31% after for example running it in a wet environment? Just to understand if it could be a device or a fw issue. Regards

[Peter S.]

Hi Eleon,

Thank you for your reaction. The value is stuck at 31%, even if I breathe on it to make it more humid. Also if I reflash the module, the value is 31%.

I also flashed the firmware on another SMARTAG device, that one also had its humidity value stuck, however it was stuck at 32% (and stayed there irrespective of humidity level or reprogramming).

Maybe the difference might be due to different factory calibration of the sensors?

https://www.st.com/resource/en/technical_note/dm00208001.pdf

Any help is appreciated, I have been looking at the firmware code for quite some time, but cannot find the issue.

Best regards,

Peter

[Peter S.]

Hi Eleon,

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Would it be possible to send me the original factory firmware that is on the device initially, to check if this is a firmware issue by flashing it? In the meantime I verified that the address that contains the humidity value on the humidity sensor always contains a 1. This converts to 31% after linear interpolation with the calibration data (and to 32% on the other device).

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Best,

Peter