Converting zigbee illuminance value to lux

[Erelen-Laiquendi]

According to Zigbee doc (4.2.2.2.1.1 and 4.3.2.4.1) and Wireshark sources (wireshark-3.2.1/epan/dissectors/packet-zbee-zcl-meas-sensing.c, line 192).

lx = 10^(value/10000)-1

So, if sensor return 14'914 - real illuminance is 30 lx.

Please, implement this for MiJia Light intensity sensor (GZCGQ01LM)

@kirovilya ?

[Erelen-Laiquendi]

100 lowest values of MiJia Light intensity sensor

SELECT DISTINCT
  CAST(state AS INT) AS `value`,
  ROUND(POWER(10, CAST(state AS INT)/10000)-1, 5) AS lx
FROM
  states
WHERE entity_id = 'sensor.kitchen_illuminance'
ORDER BY `value`
LIMIT 100;

value	lx
0	0.0 0000
3011	1.0 0032
4772	2.0 0054
6021	3.0 0037
6990	4.0 0035
7782	5.0 0067
8451	6.0 0003
9031	7.0 0018
9543	8.0 0119
10001	9.0 0230
10414	10.0 0019
10792	11.0 0052
11140	12.0 0170
11462	13.0 0232
11761	14.0 0030
12042	15.0 0295
12305	16.0 0200
12553	17.0 0114
12788	18.0 0203
13011	19.0 0322
13223	20.0 0390
13425	21.0 0392
13618	22.0 0382
13803	23.0 0491
13980	24.0 0345
14150	25.0 0160
14314	26.0 0225
14472	27.0 0271
14624	28.0 0013
14772	29.0 0544
14914	30.0 0273
15052	31.0 0369
15186	32.0 0654
15315	33.0 0165
15441	34.0 0258
15564	35.0 0808
15683	36.0 0837
15798	37.0 0144
15911	38.0 0318
16021	39.0 0369
16128	40.0 0152
16233	41.0 0490
16335	42.0 0312
16435	43.0 0479
16533	44.0 0907
16628	45.0 0447
16721	46.0 0023
16813	47.0 0650
16902	48.0 0044
16990	49.0 0345
17076	50.0 0350
17161	51.0 1157
17243	52.0 0294
17324	53.0 0078
17404	54.0 0473
17482	55.0 0154
17559	56.0 0330
17635	57.0 0962
17709	58.0 0652
17782	59.0 0674
17854	60.0 0986
17924	61.0 0119
17994	62.0 0862
18062	63.0 0295
18130	64.0 1297
18196	65.0 0852
18261	66.0 0389
18326	67.0 1426
18389	68.0 0809
18451	69.0 0032
18513	70.0 0681
18574	71.0 1119
18634	72.0 1297
18693	73.0 1164
18751	74.0 0669
18809	75.0 1512
18865	76.0 0164
18921	77.0 0097
18977	78.0 1326
19031	79.0 0184
19085	80.0 0279
19139	81.0 1627
19191	82.0 0419
19243	83.0 0401
19295	84.0 1587
19345	85.0 0031
19396	86.0 1618
19445	87.0 0351
19494	88.0 0205
19543	89.0 1191
19591	90.0 1228
19638	91.0 0258
19685	92.0 0365
19732	93.0 1562
19778	94.0 1671
19823	95.0 0636
19868	96.0 0631
19913	97.0 1668
19957	98.0 1477
20001	99.0 2303

And in reversed way: if we get any integer lux value and calculate zigbee-value from it (30 lx -> 14914) - result _exactly_ matches one of sensor value.

As you can see, internally sensor works with integer lux value. So, after converting to lux, we can round result to integer.

[Koenkk]

This can be implemented here: https://github.com/Koenkk/zigbee-herdsman-converters/blob/master/converters/fromZigbee.js#L955

How to get to formZigbee.js: https://www.zigbee2mqtt.io/how_tos/how_to_support_new_devices.html

Can you give it a shot?

[Koenkk]

Merged, thanks!