wmbus: Kamstrup Multical 21 water meter

[xenos1984]

Update: I realized that I had been using an old version (apparently the git version I compiled got installed alongside the one from the Ubuntu 20.04 repo, and the latter was given preference). With the current git version I get a lot more decoded data, even though it does not seem to make sense. I updated the issue below.

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I recorded a few samples from two Kamstrup Multical 21 water meters (cold and warm water), which are only partially decoded. The device sends data every 16 seconds, and I took samples while using water, so that the meter reading - if it is in the data - should change. There is quite a bit of information in the datasheet.

Command line: rtl_433 -f 868950000 -s 1200000 -g 15 -R 104 -M hires -M level -S known

Sample output:

time      : 2021-01-29 00:11:26.795651
model     : Wireless-MBus Mode      : C            Manufacturer: KAM         ID        : 76522329
Version   : 27           Device Type: 0x16         Device Type String: Cold Water                      Control   : 0x44          Data Length: 32           Data      : 21442d2c292352761b168d207fe2189c20e134e8e1577543a97d60942ae5c07f2d37
Integrity : CRC
Min Volume flow[0]: 2698.285 m3/min                Min Mass flow[0]: 144882.203 kg/h                   Unknown   : none
Modulation: FSK          Freq1     : 869.0 MHz     Freq2     : 869.1 MHz
RSSI      : -12.1 dB     SNR       : 18.2 dB       Noise     : -30.4 dB

Recorded data: wmbus.zip

Related issue: #1626

[merbanan]

Compare the output with the decoded parameters from the https://github.com/weetmuts/wmbusmeters/ project. You can use rtl_433 decoding as input to wmbusmeters. I sort of aim to cover the OMS spec for rtl_433. Covering all the different proprietary wmbus devices would mean I would have to re-implement all the decoding that wmbusmeters has which would be redundant.

[xenos1984]

Thanks, that worked out!

Also as a comment to future readers of this issue, it turned out that I had forgotten to use the AES keys, since the meter data is encrypted.

[merbanan]

Yeah, aes support might come in the future. But I think my time is better served in other areas. Right now wmbusmeters is much better for wmbus support.