Up on now, my script is using the
- node-red-contrib-modbus and
- node-red-contrib-buffer-parser
to access several Modbus-TCP solar devices with and without SunSpec. The script runs fine and stable for month with my dashboard. Now, there are several more devices in the house what do not have ethernet interface and use RS485 for Modbus-RTU only:
Wachendorff URDR 001 what is a hardware PID regulator
(beside the NR script based PID) and a energy multi meter
Tense TPM04-SH also using Modbus-RTU.
For the hardware wiring, TCP is a benefit as the installation is distributed over 2 buildings and network switches are already present everywhere. This way, I hesitate to tackle trying the modbus RTU by use of serial interface COM or TTY access by NR. As a possible hardware solution, I found a chinese RS485 to Eth converter what claims to do a Modbus RTU to Modbus TCP conversion.
On the other hand, this converter can be used as a pair what converts RS485 to TCP and converts back to serial interface with a second hardware converter (schematic 2) or even a virtual serial software port (schematic 3). Possibly emulating a Modbus TCP device with only one converter is the most direct way what does not require any other NR libraries. (schematic 4)
Anybody here with experience for Modbus-RTU or is it better to try the TCP approach first without using RS485 serial connection before?
Here are the 4 imaginable possibilities for connection. For 1,2,3, NR access is to (virtual) serial interface while 4 is direct Modbus TCP.
