Needs to convert RS232C signals to RS485 Modbus signals


Thread Starter


I have a system which transmits signals in RS 232C format. There is a CONTROL System, which accepts signals in RS485 Modbus Format.

Please share you thoughts as to what needs to be done to interface these to systems, i.e. how to convert RS232C signals to RS 485 Modbus.

I have only the basic knowledge of RS232C and RS 485.

Darrin Hansen

It sounds like you just need a low-cost RS232-to-RS485 converter. B&B Electronics ( offers quite a few of them for between $50.00 and $75.00 (as do many other companies).

You need a "232 to 485 converter." Automation Direct has them and surely many others. AD calls it an FA Isocon or Isonet or similar. Theirs features isolation and automatic switching of the 485 driver enable.
And place the converter close to the RS232 system! RS232 is not suitable for connections >10m, that's why they use RS485.
You are mixing terminologies. RS 232 and 485 are electrical specifications. Modbus is a communications protocol. If your device is using Modbus on a RS232 line, then you need a 232 to 485 converter. If your device does not use Modbus, then you will not be able to communicate with the control system.

Very interesting device: Modbus RTU Serial Gateway

I would like to know if it is possible to find cheaper devices with the same function of translating an ASCII RS232 into a modbus RS485?

Thank you,
An old PC and some software will do that.

But if it's converting from Modbus ASCII to Modbus RTU there will need to be some intelligence involved someplace so a simple converter won't do it.

You could probably program a $99 Click PLC to do it since it supports both and has a 232 port and a 485 port. That would be my first attempt at it.

there are lots of vendors who give rs 2323 to 485 convertors. i use MOXA convertor which is a basic one and really does the job. u can opt for a moxa convertor.