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Visitor II
June 22, 2020
Question

Temperature reading from IIS3DWB

  • June 22, 2020
  • 1 reply
  • 682 views

Can't figure out how to read or interpret the temperature reading from this MEM.

I read the two register 20h and 21h and get an answer like this:

RM20h02h14FFh

The very brief description in the spec sheet did not help me.

Has anyone a hint?

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    1 reply

    ST Employee
    June 22, 2020

    Hi @Balanceman​ , I suggest you to check the datasheet p.7 together with the online C drivers for IIS3DWB on Github, especially the iis3dwb_reg.c source code:

    float_t iis3dwb_from_lsb_to_celsius(int16_t lsb)
    {
     return (((float_t)lsb / 256.0f) + 25.0f);
    }

    In you case, if I well understand:

    • REG 20h (OUT_TEMP_L) value --> 14h
    • REG 21h value (OUT_TEMP_H) --> FFh

    You have to:

    1. Concatenate the two registers, starting from MSB --> FF14h
    2. Transpose to decimal using two's complement conversion --> -236
    3. Divide by temperature sensitivity (256 LSB/°C) --> -0.922°C
    4. Sum 25°C (the default temperature calibration), and you'll get about --> 24.08°C

    Regards