After I found out the pinout of the Sunny Boy 2100TL inverter I build the UART piggyback and it is working fine. Now, it’s time to build the RS485 version.
Because I didn’t want to use an external power supply for the galvanic isolated output side I used an (expensive) 5V DC/DC converter. The pictures below shows the design:
For testing I was using a RS485 to RS232 adapter from ADAM:
Finally, I was able to connect to the SMA Logging program: