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 following modules contain an activatable terminating resistor: RevPi Connect SE, RevPi Connect and RevPi Connect S:

https://revolutionpi.com/en/tutorials/serielle-geraete-anschliessen-compact

https://youtu.be/guzrFgp7Sx8

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

Take a look at the Tutorial 21 – Modbus RTU Master https://revolutionpi.com/tutorials/video-tutorials/?noredirect=en_US#VT21

Knowledge Base Support

RS-485 Checklist

Analytics

Problem

Solution

Related articles

Related content