Register IDs for Kamstrup electricity meter

[amorsen]

PyKMP is working great for an unencrypted Kamstrup 382 electrical meter.

$ pykmp-tool -d /dev/ttyUSB0 get-register --register 1 --register 2 --register 0x000d --register 0x000e --register 0x041e --register 0x041f --register 0x0420 ; pykmp-tool -d /dev/ttyUSB0 get-register --register 0x0434   --register 0x0435 --register 0x0436 ; pykmp-tool -d /dev/ttyUSB0 get-register --register 0x03ff --register 0x0438 --register 0x0439 --register 0x043a --register 0x400 --register 0x0540 
WARNING:pykmp.tool.__main__:Unknown register ID(s); please report this if you have more information.
GetRegister response(s):
   1 → <unknown reg 1>  = 53740 kWh
   2 → <unknown reg 2>  = 0 kWh
  13 → <unknown reg 13> = 3740.1417 kWh
  14 → <unknown reg 14> = 0.2849 kWh
1054 → <unknown reg 1054> = 229 V
1055 → <unknown reg 1055> = 229 V
1056 → <unknown reg 1056> = 228 V
WARNING:pykmp.tool.__main__:Unknown register ID(s); please report this if you have more information.
GetRegister response(s):
1076 → <unknown reg 1076> = 0.75 A
1077 → <unknown reg 1077> = 0.55 A
1078 → <unknown reg 1078> = 1.66 A
WARNING:pykmp.tool.__main__:Unknown register ID(s); please report this if you have more information.
GetRegister response(s):
1023 → <unknown reg 1023> = 0.435 kW
1080 → <unknown reg 1080> = 0.061 kW
1081 → <unknown reg 1081> = 0.076 kW
1082 → <unknown reg 1082> = 0.298 kW
1024 → <unknown reg 1024> = 0.000 kW

The register numbers are taken from https://github.com/bsdphk/PyKamstrup. They correspond to:

1: Total energy in (all phases)
2: Total energy out (all phases)
13: Total energy in hi-res (all phases)
14: Total energy out hi-res (all phases)
1054: Voltage L1
1055: Voltage L2
1056: Voltage L3
1076: Current L1
1077: Current L2
1078: Current L3
1023: Power in (all phases)
1080: Power in L1
1081: Power in L2
1082: Power in L3
1024: Power out (all phases)

There are undoubtedly also per-phase measurements for outgoing power, but I do not have solar cells or battery, so I cannot test that.

The hi-res value appears to consist of the last 3 digits of the regular value + 4 decimals. This makes it possible, if a bit annoying, to reconstruct the full value in high resolution.

[gertvdijk]

Thanks for adding a link to the other project implementing those registers to add support for another meter! 👍🏼
Good to see it basically works on your meter and there are mostly cosmetic issues it seems. The description parts for the registers should be self-explanatory to add in src/pykmp/constants.py.

The hi-res value appears to consist of the last 3 digits of the regular value + 4 decimals. This makes it possible, if a bit annoying, to reconstruct the full value in high resolution.

Ah, yes, I see what you mean. I guess it would also apply to the 403 model here, but my values are rather low and I don't have any overflow in there yet.
It may be a bit cumbersome to make that work elegantly... I prefer to explore if it can work in a generic way rather than special casing "if model X, register Y and Z, then ...".

Two main issues I see:

• how to enrich the data of two register responses in a generic way? is it always the same number of digits or "it depends"? 🤔
• an API to define which register IDs to 'glue' together and by how many digits to shift and add? and perhaps an automatic enriched output by default if the hi-res register is requested.

Either way, perhaps it would be best to have the raw output, if you're willing to share that. Include -vv in the command you ran - with that I could add some realistic test cases!

If you're aware of other raw data available for the same or similar meters, please point me to it, I love to work with concrete examples test-driven. 😄

[amorsen]

I have attached the output of the same commands but with -vv.

pykmp-new-register.log

The hi-res registers are included purely for verification purposes. They are not intended for use by the electricity company or the end user. However, they ARE really convenient to use and definitely the preferred way to get consumption/production information into Home Assistant.

The nifty thing is that there is redundancy between the two registers. A read can be done this way:

1. Read register 1, get 53740 kWh
2. Read register 13, get 3740.1417 kWh
3. Extract the digits before the decimal point, "3740"
4. Compare to the last digits from register 1.
5. If the comparison matches, replace the digits before the decimal point with the digits from register 1

If the comparison fails, there are three cases
a) Reading from register 13 is 1 higher than reading from register 1. In that case the singles digit changed between the two reads. Add one the reading from register 1 and do 5)
b) Reading from register 13 was a sequence of zeros, whereas the matching digits were nines in register 1. In that case register 13 overflowed between the reads. This is handled the same as case a)
c) Neither of those, in which case the read should either retry or just fail. I do not see a realistic scenario where that could happen, but who knows.

I think it would be best to let the API user specify that they are trying to read a register pair. get-register --register 1,13 to get the extra digits from 13.

Perhaps provide a list of known paired registers, so you can do get-register --paired-register 1, and that will automatically pick up the extra digits from 13.

Either way, thank you very much for creating PyKMP.