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I am attempting to retrieve data from a SDM230 Modbus RTU Meter using a raspberry Pi running minimalmodbus (python3).

The response every time is:

Response from instrument: 01 03 02 00 00 B8 44 (7 bytes)

or if I request with read_float() four bytes:

Response from instrument: 01 03 08 00 00 00 00 00 00 00 00 95 D7 (13 bytes)

and the voltage value (register starts at 0) is 0.0.

Update 2023-05-23 22:16 I've found a posting for SDM220 Modbus Meter. The procedures/methods there are very similar to mine. This meter is a predecessor model of mine.
I can therefore not completely rule out that my measuring device has a quirk.

I have already contacted the supplier (B+G) and will update the question if I receive a response.

Brits
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bitman
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  • You might get ore responses at [raspberrypi.se]. – SiKing May 23 '23 at 18:43
  • It you are getting a valid response (and you are) then the issue is with your request or the SDM230 (and the fact you are using a Pi is irrelevant). It looks like you are requesting holding registers (function code `03`) when the info you want is in input registers (function code `04`). The Modicon numbering scheme used in the documentation can be a bit confusing... – Brits May 23 '23 at 20:46
  • It would be much easier if you'd provided the code you wrote to interface to the SDM220 and if you could show your out-going (TX) commands as well, not just the RX. – Nick S. May 25 '23 at 17:18

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