weather:bit Air Pressure reading from BME280 incorrect.

Development Boards MicroMod
1

I am using the weather:bits to record air pressure readings as part of a project with primary school children. I have loaded the sparkfun weather:bit extension in to the MicroBit Makecode and have followed the microclimate kit experiment guide https://learn.sparkfun.com/tutorials/mi … d-pressure

Whilst I get rational results for both Humidity and Temperature that is not true for air pressure. To test the hardware and software operation I have also loaded 2 other extensions; BME280 and Enviro:Bit in order to compare results. Comparison results for Weather:Bit, BME280 and Enviro:Bit respectively are as follows:

Temperature 21 , 22, 22.

Air Pressure 27, 1021.49, 1021.

Humidity 52, 52, 53.

The 27 result from the weather:bit is not correct. The hPA figures from the other software are correct. All 3 are using the same hardware.

I think that both the BME280 and the EnviroBit use the 32bit software alternative in the BME280 datasheet but weather:bit uses the 64bit software option (because it uses C++?), which requires the conversion from Q24.8 format which I assume is the division by 255 outlined in your documentation. Your documentation states that an 8 digit number should be returned by a call to read the pressure and only a 6 digit number is displayed.

Any help to clarify / correct this would be gratefully received.

Bob.

2

I’m not sure how makecode works (internally with the extensions); however, if the bad data point is only at the start of the data set, maybe it is just happens to be an erroneous data point from the sensor starting up and you can just ignore it? (just guessing)