I’ve been trying for days to integrate my Systemair SAVE VSR300 into Home Assistant. However, I’m already stuck at the first step: establishing a working Modbus connection.
I’m using this Modbus adapter from Waveshare:
I’ve taken a picture of my circuit board (see attachment).
So far, I’ve connected the Waveshare to the 4-pin gray terminal block in the upper right corner, next to the RJ11 port (where the control unit is connected). I’ve left the ground, a, and b pins unused, and the 12V pins are disconnected. When the Waveshare is connected here, the blue action LED immediately starts flashing wildly, but always at the same rate (period: 1 second). I configured the Waveshare according to the system’s Modbus settings: Baud rate: 19200, Address: 1, Parity: none → although I also tried other values on the system side. The result in QModMaster is always the same: timeout.
I also have an RJ45 breakout adapter available. However, I don’t know the pin assignment. I’m also unsure whether this slot is intended for external management systems or only for Systemair devices. I would be extremely grateful for any hints or solutions from the community. I’m happy to provide any necessary information.
Ronny you have my sympathy trying to get Modbus to work. It has been a while since I configured serial modbus but I can share a few steps that I would start with. I would first confirm that the modbus coming from the control unit is what you expect. To do this, I would use a serial(usb) to modbus converter plugged into my laptop and then use a program called Modscan32 to read and write commands to the control unit. This will allow you to confirm that the unit is actually sending modbus on the serial link and it is a version of mobus that is readable, and your communication parameters are correct. You will either need a straight through or a null modem serial cable to connect the converter to the control unit. If you are using breakout boxes, the pinouts are available on the interwebs. Once you do that, you use the serial converter to hookup to the Waveshare and us Modsim32 to confirm the modbus over ethernet is what you expect in HA. I know this is a little vague but like I said it has been a while.
First of all, thank you so much for your help with my problem. I’ve now used the Waveshare USB-to-RS485 adapter. Initially, I connected it to the RJ45 breakout cable. The breakout adapter itself was plugged into the RJ45 port on the motherboard. In modscan64 I only got a timeout error for all possible wiring combinations.
Next, I connected the USB adapter to the 4-pin connector to the left of the control unit’s connection port (black cable). I also tried swapping A and B.
Assuming my WaveShare is configured correctly and properly connected to the system’s circuit board, the SystemAir integration setup should work, right? Manually reading the data would just be a preliminary test, not strictly necessary. Is this assumption correct?
I’ll conduct further tests this week and post more detailed pictures and settings.
Something else I’ve noticed:
“When the WaveShare is connected here, the blue action LED immediately starts flashing wildly, but always at the same rate (period: 1 second)”
→ the control unit’s backlight flickers in exactly the same way.
I’ve now ordered an RJ9 splitter (the control unit is plugged into an RJ9 port on the circuit board).
I also have the Elfin EW11a. I’ll then follow the linked instructions exactly. The instructions mention a baud rate of 115200, which surprises me somewhat. My system’s control unit shows 9600 in the Modbus settings - I can only select 19200 here.
A Systemair SAVE or Legacy Residential / D24810 ventilation unit with accessible Modbus RS485 port.
A USB-to-Modbus RS485 converter connected to your Home Assistant server.
The serial port path (e.g., /dev/ttyUSB0 on Linux, COM3 on Windows).
Communication parameters (usually 19200 baud, 8 data bits, no parity, 1 stop bit).
and see if it helps.
I use now this integration with my Systemair VTR500 and Connection Method 1: Modbus TCP (SAVECONNECT 1.0)
A Systemair SAVE or Legacy Residential / D24810 ventilation unit with Modbus TCP access, using SAVECONNECT 1.0 (IAM) or another Modbus TCP-to-RTU converter.
The module must be connected to the same local network as your Home Assistant instance.
You need to know the IP address of the module. You can typically find this in your router’s client list.
and it works great.
Method 2 with the Waveshare Modbus to Ethernet adapter.
Method 2 just tried again with the Waveshare serial-to-USB adapter.
I’ve taken screenshots (see below). Parity is set to “none” everywhere.
With QmodMaster, I keep getting a timeout when trying to read the holding registers.
I’ve now used the RJ45 connector on the board again (labeled Modbus). According to my research, this 4-pin terminal, labeled “12V, Gnd, A, B,” is an internal serial interface, to which the control unit is also connected.
Using an RJ45 breakout adapter, I connected TA and TB from the Waveshare to pins 5 and 4 of the RJ45 “Modbus” connector. I also tried swapping the two wires on these two pins. However, I’m still only getting timeouts. So I’m not getting any data at all – not even “incorrect” data.
Why are PINs 4 and 5 involved? → I’ve done extensive research using chatgpt and gemini.
In norway we have a user forum which discussed problems using modbus with VTR300. Use Google translate and read more about it here: Modbus - Home Assistant - Hjemmeautomasjon
I hope you can find out of of the problem.
