The Setup - Daniel make Gas analysers are connected to LD485A on RS485 2 wire half duplex communication.

The LD485A output is RS232 is connected to Bridge BM85 port 3. The port 3 is set as slave, ID is 3 which is same as GC ID 3.

POrt1 of BM85 is set as master, & a PC is communicating to it (PC looks at GC as slave with an ID as 73 as i.e. mapped ID of bridgeMux)
The settings are 9600,8,1,odd parity.

Problem - The PC cannot communicate to Daniel GC through BM85. Daniel GC/LD485A to PC works fine when directly connected.
Similarly if I connect 2 PC to the ports of Bridge mux it works fine. But Bridge mux cannot recognize GC, the Pc gives error Invalid address.

The Bridge mux port 3 also never blinks while Port1 is trying to communicate. I have used straight, crossed, null modem type cables, still problem persists.

I have tried vairous Modbus master tools & the Daniel Mon Modbus test biult in tool, but no results. Any solution to above problem will be much helpful & appreciated.

Thanks,
techman

 

On both ends of your RS-232 cable (DB9) jumper the RTS (pin 7) with the CTS (pin 8); and jumper DSR (pin 6) to DTR (pin 4). It might be that the BM85 is waiting to see a high DSR (pin 6) and a high CTS (pin 8).

Give me a shout if you need any further clarification. My email is ahalim [at] ualberta [dot] net