Modbus Testing Through Modscan


Thread Starter


Dear All,

I could not get the results with modscan software to test the Modbus connection for the digital relays. The modscan software says "Modbus message timed out". I have connected the LAN Cable (CAT 6, Untwisted pair) to the RS-485 terminals (Ground, A-, B+). Here is what I have done:

Physical connection:

1. Lan cable (with RJ 45 connector and all the 8 cores connected inside the RJ 45 connector) connected to TSX CUSB 485.

2. The other end of LAN cable connected to the relay RS-485 terminals (ground, A-, B+).

Here, Core No: 8 connected to Ground
Core No: 4 connected to B+
Core No: 5 connected to A-

3. USB connection of TSX CUSB 485 connected to PC

4. The rotary switch of TSX CUSB 485 is set at position 3 (other direct)

Software setting:
All the parameters are matched for the modscan software with the digital relays (Baud rate:9600, Parity: Even, Data bits and stop bits settings not available to set in the digital relay but set as 8 and 1 respectively in modscan software.

Sorry if this is too obvious, but you didn't mention that you have Modscan connecting through the appropriate com port.

The default port for Modscan is probably 1, which will almost definitely be incorrect. Look in device manager under Ports (Com and LPT) to determine the correct port, and also to verify the TSX CUSB 485 drivers installed correctly.

Once you've verified this, if it still doesn't work try reversing wires 4 and 5.

You might also try different software such as Chipkin Automation Systems Modbus Scanner -