Can I use RS-485 port as RS-232

[digdug]

I have a PCI-485/2 board. I have one of the ports connected to a devices using RS485 protocol. Can I use the other port and connect it to a RS232 device?

[Chris_Rake]

Not directly. RS-485 is a differential bus whereas RS-232 is a single-ended bus. There are some off-the-shelf convertors that go between RS-485 and RS-232, but some of them have datarate limitations.

[digdug]

Chris - so there is no way to enable one port as a RS-485 and the 2nd part as a RS-232 on the PCI-485/2 board? If not, can you recommend a converter?

Thanks

[Chris_Rake]

The physical transceivers for RS-232 and RS-485 are different, and thus are not configurable. With regards to the converter, I do not have any specific recommendations, but a quick glance at the B&B Electronics catalog shows a couple of dozen different options that run from $70-$125. Which model you need will depend on the features you're looking for: connectors, max baud rate, surge protection, power source, isolation, etc.

[mhead]

Yes you can. From the 485 card, attach a 1 Kohm resistor to pin 4 and another to pin 8. Tie the other end of both resistors together and attach to pin 1. This line then gets run to pin 5 of the RS232 connector. Now from the 485 to the 232, run pin 9 to 3 and then pin 5 to 2. The shield will run from pin 1 of the 485 to pin 1 of the 232. Lastly, if necessary, on the 232 side, some equipment needs pin 7 and 6 tied together.

[jEdward]

I tried this and it works great!!! Thanks

[kpak]

Black Box makes a pretty good RS-485/RS-232 converters. Regardless of the brand, make sure you have the correct switch setting which you can perform on circuit panel.

[Siddu 140]

Hi,

You can go for the converters from SuperLogics or Maxim.

http://www.superlogics.com

http://www.maxim-ic.com/

Regards,
Siddu