I created a Modbus to RS485 connection using the Runcci Yun USB adapter. Cables neatly tinned and carefully connected.
The good news: It worked, I installed the integration via HACS, “played through” the configuration wizard and the data appeared. Daily production, total consumption etc.
However, Hacs pointed out that a restart was due.
Since then it no longer worked, I got the following message:
Modbus Error: [Connection] Failed to connect[ModbusSerialClient pollserial:///dev/ttyUSB0:0]
I then unplugged the USB adapter and plugged it back in and the values appeared again. But that probably only lasted half an hour, then the connection was lost again.
The problem remains. USB out and back in, data is displayed, then after a few minutes connection gone, no data displayed except
Modbus Error: [Connection] Failed to connect[ModbusSerialClient pollserial:///dev/ttyUSB0:0]
I then tried it once or twice more and then I had a moment of shock: it had apparently shot the entire Home Assistant. No more access to the Yaml, all entities gone. No access to backups (at least the local backups, I still have some online). Even a restart via the interface was not possible. Fortunately, when I disconnected the Pi4 from the power supply and reconnected it, everything still worked.
Could the Modbus RUNCCI connector have caused a short? Anything else would be a strange coincidence.