i have some problems with my Modbus RTU communication.
After many polls (50.000+) with Modbus Poll software as master and only one device connected to the bus with the configuration 9600 Baud, 8 Databits, no Parity, 1 Stop Bit i get a permanent Timeout Error with my galvanic isolated rs485 connector. I did measurements with an oscilloscope and my galvanic isolated rs4854 connector.
The following picture shows the result:
Galvanic isolated rs485 connector, fails after some thousand polls
First look at this picture and the voltage levels seems correct. It seems that the last byte is the only thing that could lead to a permanent timeout error with the galvanic isolated rs485 connector?
I tried some other Modbus RTU configurations but this fails as well and i get a permanent Timeout Error with my galvanic isolated rs485 connector.
Furthermore i did measurements with a non galvanic isolated rs485 connector / my galvanic isolated rs485 connector with A and GND connected.
The following pictures showing the results:
Galvanic isolated rs485 connector with A and GND connected, works fine for million+ polls
Non galvanic isolated rs485 connector, works fine for million+ polls
First look at this pictures and voltage levels seems correct and there is no extra byte at the end of the Rx packet.