I’ll do a combined answer here and not only to to your latest post. Hopefully it doesn’t get too messy…
I also have an USB RS485 adapter that I believe (but do not know for sure, never used it) I can connect there.
It has two wires only and identifies as a
Bus 001 Device 005: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter
(it has 2 wire inputs labelled A and B).
Well, first things first. You somehow need to verify the device that it actually is the right kind of adapter. I googled and found some topics about wrong linux usb drivers getting installed. So nothing definite there. On the other hand, A and B connectors that you are seeing definitely suggests that it is a RS485 adapter.
When I do smarthome:send FanSpeed 2 to the FanSpeed channel for a test I get
and the thing drops offline and reconnects.
At times (some interval presumably) I’m seeing
I assume the serial connection is not properly working yet.
There is a retry count of 5 (500ms apart) for sending commands to the unit and if it fails, it reconnects. Made to recover from possible connection problems/drops. Things happening in the last log snippet does indeed happen at fixed rate and refreshes all channels linked at that time. And no, it is not working. Serial port is opened properly but no vallox telegrams is seen. Did you have log level set to TRACE or only DEBUG?
Also, to restate, this is a MV unit which is already accessible via modbus/TCP and I’m trying to
connect via serial in addition to this.
Does the binding support this (there was a mention of MV support being dropped) ?
I have never tried connecting to a MV model unit with this binding so I don’t know. I dropped the support for MV models because at that time when I had a PR open reviewers said it should be done later because of backward compatibility. After that I never got to the point that it would be merged. And as an unofficial binding I think this should not overlap with a official binding so I left it as is. But let’s figure out if it can be done?
I tried with different RS485 adapters, with or without termination resistor but no luck on my MV unit
Ok. I think after this we can be sure that it’s not a question about wrong adapters. It just is not using the same protocol.
Is this guessing of yours or do you have any indication?
Based on what you wrote here and what I found in both models manuals. MB_A and MB_B connectors are for external connection and RS_A and RS_B is for internal communication for sensors and control panels. Both use modbus RTU. So if you want to connect your home automation system to your MV unit you use that external connection. And for example humidity sensors connect to the internal RS485 interface. To verify this you could take a dump of the serial traffic seen by your adapter when connected to RS_A and RS_B connectors. We should see modbus traffic there.
Do you think my setup (see post above) that didn’t do with my MV could still work with those SEs ?
Can I daisy chain their RS ports and use a single adapter on just one of them ?
Yes if you connect your adapter to a SE model and use this binding it sure will work. Assuming that all hardware stuff is connected and working properly.
Chaining multiple SE units to one adapter will most likely not work (now I’m kind of guessing). I would setup your three units with three adapters and create three things with the binding. Totally separate units.
Vendor told me you cannot set RS bus addresses on SE units so they all have the same by default, but from my understanding of the RS485 serial bus they would all react to commands. Not sure what happens if your binding command is ACK’ed 3 times though.
Your vendor is correct. The protocol states that a telegrams first byte is domain byte that is always 01 and is not changeable. So multiple units in one bus was first planned but newer implemented by vallox.
I’m not sure either how things would go. I’m just thinking of the situation when three different units try to send different values for example temperatures when heat recovery cell is at different melting points in each unit. I think there will too much conflicts and at least control panels will enter in failed state.