Converting zigbee illuminance value to lux

[tcwj2008]

According to Zigbee doc (4.2.2.2.1)

MeasuredValue = 10000 * LOG10( lx )+1

so converting zigbee illuminance value to lux should be

lx = 10^((MeasuredValue-1)/10000)

not
lx = 10^(MeasuredValue/10000)-1

[Koenkk]

Fixed, thanks!

[Koenkk]

I'm wondering wether this calculation is correct, in case of MeasuredValue 0, 1 is returned now (Koenkk/zigbee2mqtt#4211)

Shouldn't it be (Math.pow(10, illuminance) - 1) / 10000 ?

[sjorge]

Any consensus on this?

[Koenkk]

@tcwj2008 could you please check #1506 (comment) , if I don't hear anything I assume (Math.pow(10, illuminance) - 1) / 10000 is OK.

[Koenkk]

Reverted it back to the old calculation.

[presslab-us]

I believe the new calculation is correct, but there also needs to be a special case for 0. The documentation states: ”0x0000 indicates a value of Illuminance that is too low to be measured." So if MeasuredValue == 0, then lx = 0. Otherwise use the new calculation.

[Koenkk]

@presslab-us good to know, I've added it know with a check on 0 value.