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UtilitechAS / amsreader-firmware

ESP8266 and ESP32 compatible firmware to read, interpret and publish data to MQTT from smart electrical meters, both DLMS and DSMR is supported
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Timezone offset of DLMS timestamp #809

Open dbeinder opened 2 weeks ago

dbeinder commented 2 weeks ago

I'm not 100% certain if this is a bug in AMS Reader or if I'm reading the spec wrong and it is an implementation fail of my meter ;)

Meter: Kaifa MA309MH4LAT1 Austria/Vorarlbergnetz

Basically I think deviation should be added, not subtracted: https://github.com/UtilitechAS/amsreader-firmware/blob/81b3aacc4d66c0b3c60c616a7303d0e2ec1f2435/lib/AmsDecoder/src/Cosem.cpp#L26-L28

I'm reading the spec to mean that the date/time fields are always local time and deviation is how much needs to be added to get to UTC: image https://github.com/dbeinder/KsmWestKaifaReader/raw/master/spec/Blue-Book-Ed-122-Excerpt.pdf (page 33)

This is a decrypted DLMS frame of my meter, captured at 2024-06-15 20:23:45+02:00: dlms.zip It reports 2024-06-15 20:23:45 in the date/time fields, and a deviation of -120.

The current AMS Reader code turns this into meterTimestamp = 1718490225 (2024-06-15 22:23:45 UTC) instead of meterTimestamp = 1718475825 (2024-06-15 18:23:45 UTC)

gskjold commented 2 weeks ago

Absolutely right, thank you! 07e8 06 0f 06 14 17 2d 00 ff88 80 2024-06-15 SAT 20:23:45.000 -120 (0x80 == daylight saving active)

I think this may be the first meter I've seen where the deviation field is used, most meters report 0x8000