Temperature measurement from Pmod Nav barometer chip.

[rmac]

I am trying to read the temperature from the barometer (LPS25HB) on the Pmod Nav board.  Per the data sheet this is in a two byte register (L=2B, H=2C).  I can read the data, which is supposed to be in 2's complement format.  Typical readings at room temperature are: H = 11011001, L=10111011.  In 2's complement format this temperature is negative.  Room temperature is not negative in any units I am familiar with.  I assume the units are degrees C.  What do I do with this data to calculate the temperature?

By the way, the barometric pressure reading works fine.

[artvvb]

Hi @rmac, welcome to the forums.

The temperature counts need to have an offset and scale applied. Please review this technical note for the LPS25HB part describing how to convert from sensor counts to pressure and temperature in hPa and degrees C: https://www.st.com/resource/en/technical_note/tn1228-how-to-interpret-pressure-and-temperature-readings-in-the-lps25hb-pressure-sensor-stmicroelectronics.pdf.

Thanks,

Arthur

[rmac]

Thanks Arthur:

The 42.5 degree offset was the part I was missing.  The data sheet for the LPS25HB gave the 480 count/degree scaling factor but no mention of an offset.  All is good now.

Thanks for your quick response.

Richard