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yozik04 / nibe

Library for communication with Nibe heatpumps.
GNU General Public License v3.0
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Modbus problem writing negative degree-minutes #133

Open zlorf opened 7 months ago

zlorf commented 7 months ago

It was a problem on 2.4, it's still not working on 2.5.1.

Python 3.9.2, Nibe S320. Tested on 2.4 and 2.5.1

Whenever I try to write degreeminutes field (which is usually negative), it gets stored as 0. I did some deep-down debugging and it was really weird, as the bytes were similar. If I tried to write what I've received from modbus, the library send the same stream of bytes, and yet value got reset to 0.

I then discovered (by trials and errors, honestly), that if I reverse the list of registers:

connection = Modbus(heatpump=heatpump, url="tcp://" + NIBE_IP + ":502", slave_id=1)
# Patch write method to work with degreeminutes
orig = connection._client.write_registers
connection._client.write_registers = lambda slave_id, starting_address, values: orig(slave_id, starting_address, list(reversed(values)))

then it works... as long as I stay on the same side of 0. That is: if DM are already negative, I can write any negative number correctly. But if they are positive, then writing negative number results in 0. I haven't tried writing positive number when DM is negative.

I really wonder if this is maybe a fault with my heatpump. But maybe you have an idea what is wrong. s32 type is little tricky. No rush, as the workaround does the trick for me.

elupus commented 7 months ago

Since im curious. Can you test to see if behaviour changes depending on if python numpy is installed?

elupus commented 7 months ago

Oh right you say you art the network trace. If you read and write same raw data in the trace it really should work. So then it does seem like a pump bug.