BME280 sensor.

[richard]

henrik here is a json dump from my nodemcu/bme280 regs from 0x80 to 0xff
{"bme":144,111,137,51,54,42,151,6,185,109,247,104, 50,0,61,148,200,214,208,11,181,32,73,255,249,255,1 72,38,10,216,189,16,0,75,61,0,0,0,0,0,0,0,0,0,51,0 ,0,192,0,84,0,0,0,0,96,2,0,1,255,255,31,78,8,0,0,6 4,183,255,0,0,0,0,5,0,0,0,0,0,0,0,96,0,0,0,0,0,0,0 ,0,0,0,0,0,0,0,0,0,101,1,0,20,43,3,30,189,65,255,2 55,255,255,255,255,255,0,5,12,183,0,0,72,115,224,1 26,150,48,112,242,128} and the highlighted corresponding readings
{"pressure":1011,"roomt":22.06,"humidity":42,"setpoint":27,"damper":1800,"state":1,"fire":21," bv":1340}

ps
hope it's ok looks like forum is not json friendly

[HenrikOlsson]

Thank you Richard, that did help.

I've got pressure working as well.
Temperature is within 0.05°C and pressure is within 1Pa compared to a commercially available BME280 based sensor module.
I thought I had humidity working although it read about 7% off compared to "real" one but today the difference is 30% so there must be something wrong still.

Will look at that later and hopefully be able to post some code.

But geez, these LONG math operatations eats away code space, 8k at the moment.

/Henrik.

[Ioannis]

There is always the possibility that humidity sensor may not had time to sense the environment. Or the other reference sensor is in a bit different position and gives wrong measures.

In my experience, humidity sensors are not very trusty.

[HenrikOlsson]

Richard,
Out of curiosity, have you tried the PBP code you posted with negative temperature values?

The reason I ask is that my temperature compensation code was pretty much exactly like yours but it went belly up as soon as the temperature went below 0°C.
Reason mainly being the shift operations where potentially negative values (T2, T3 and therfor t_fine) are involved.

I see you're handling the compensation values quite differently, simply pushing them into the lower 16bits of a LONG no matter if they're positive or negative. With that said, both T2 and T3 are positive in my case, like in yours, but they could potentially BE negative and then I don't think simplt stuffing the "signed short" into the lower 16bits of our LONG will work properly.

I had to replace the affected shift operations with * and / at quite some cost for the execution time and for any compensation values specified as signed I'm doing this sort of thing:

    ' dig_T2, signed, read to temporary variable and cast to LONG to preserve sign of value
    SHIFTIN BME280_MISO, BME280_CLK, 6, [tmp_W.BYTE0, tmp_W.BYTE1]
        IF tmp_W.15 = 1 THEN
            dig_T2 = -ABS(tmp_W)
        ELSE
            dig_T2 = tmp_W
        ENDIF

/Henrik.

/Henrik.

[richard]

Out of curiosity, have you tried the PBP code you posted with negative temperature values?

sorry no, i never actually used pbp for these sensors after discovering the real potential of esp chips


if the upper word was set appropriately here maybe that would help , adc_t might need similar treatment but the calculation should be
then ok ,i think?

    T1.Byte0 = IIC_RX[0]                            ' Calibration data into Unsigned Word
       T1.Byte1 = IIC_RX[1]
    T2.Byte0 = IIC_RX[2]                            ' Calibration data into Signed Long
       T2.Byte1 = IIC_RX[3]
    if  IIC_RX[3].7 then 
      T2.Byte3=255
      T2.Byte4=255
    else
      T2.Byte3=0
      T2.Byte4=0
    endif
    T3.Byte0 = IIC_RX[4]                            ' Calibration data into Signed Long
       T3.Byte1 = IIC_RX[5]
    if  IIC_RX[5].7 then 
      T3.Byte3=255
     T3.Byte4=255
   else
      T3.Byte3=0
      T3.Byte4=0
   endif

[richard]

the calculation should be
then ok ,i think?

nah, pbp needs a signed shift right command too. too hard me thinks. pic chip in bin, esp wins

[HenrikOlsson]

For anyone who are still interested in using this sensor with PBP I've posted my code as an example in the Wiki:
http://www.picbasic.co.uk/forum/cont...BME280-Example

If any questions or suggestions should pop up I suggest we keep them in this thread.

/Henrik.