Usage information MTreg

[coelner]

As you can see, I used the MTreg value to capture outdoor light.

It reveals an error. The esp8266 is in deep sleep, therefore it restart completely and the saved MTreg value in the library get lost. But the sensor itself uses another MTreg value. I have no idea how to solve the problem in a nice way, but some thoughts:

1. include in begin() some resetting to the default MTreg
2. get/set method to manipulate the saved MTreg in the library space
3. inform the user to take care of this behavior
4. (find a hidden possibility to get the current MTreg from the sensor itself)

[bjarnebuchmann]

I can confirm this issue.
The problem is that the BH1750 library does not always write the default MTreg to the device upon begin(). Rather, it assumes (sometimes falsely so) that the device uses the default MTreg on start. That is not true, if the program is reset (eg waking from deep sleep or rebooting) without giving a full power interrupt, which could reset MTreg on the BH1750.
The solution seems straight forward: setup() should always call

setMTreg( (byte) BH1750_MTreg )
or alt
setMTreg( (byte)BH1750_DEFAULT_MTREG )

to ensure that MTreg on device (BH1750) and object (library) mathches.

/Bjarne

[bjarnebuchmann]

As a work-around, I will suggest to manually call setMTreg() right after begin(), as per:

setup(){
...
  lightMeter.begin(BH1750::CONTINUOUS_HIGH_RES_MODE);
  lightMeter.setMTreg((byte) BH1750_DEFAULT_MTREG);
...
}

[coelner]

BH1750/src/BH1750.cpp

Line 79 in 38e9f37

return configure(mode);

@claws what about this?
return (configure(mode) && setMTreg((byte) BH1750_DEFAULT_MTREG))