RS-485 Checklist
Problem
You want to communicate over Modbus-RTU and there are suspicious errors. The underlying bus is RS-485.
Solution
There is only one Modbus Client on the RS485 bus
There is one bus with two ends without Y-branch
There is a bus termination of 120 Ohm at both ends of the bus
The P and N lines are correctly wired at all communication partners
The baud rate of the communication partners is known and correctly set at the Modbus Clients and all Modbus Servers
The parameters of the serial connection are known and correctly set by each communication partner:
baud rate
parity
start bits
stop bits