RS-485 serial port on PC?


Thread Starter


Would like to configure Moore Industry module, which requires RS-485 communication to PC. My question here is: does every PC have at least one port (COM1 or COM2) with rs485 communication? (if yes, how do I know which port is 485). or do I have to use 485-to-232 converter? thank you very much for your time,
On standard PC you have only RS232 ports. You have to use either external converter or internal PC card to have RS485 ports.

It can be different with industrial PCs, some vendors offer an industrial PC models with built in RS485 or RS422 ports. In this case you always have a description of PC configuration and port location.

Have a nice day.

Most PCs come with a serial port but its configured for RS232 comunications. You will need to convert the RS485 to RS232. Its done all the time in the PLC world.

James Ingraham

No, most PCs do not have an RS-485 port. You will need either an add-in board or a converter.

There are "industrial" motherboards out there with built-in RS-485, e.g Advantech or Kontron. But you would know you had it because it would not be a an off-the-shelf PC a la Dell or HP.

-James Ingraham
Sage Automation, Inc.

Daniel Chartier

Hello Song;

Standard commercial PCs used to have RS-232 ports (most recent laptops do not even have them as standard features, tyhey are now called "legacy ports"). Unless you have a specially designed PC, you will have to use a RS-232 to RS-485 converter, or a RS-485 add-on port card.

Hope this helps,
Daniel Chartier
No nearly all PC's comm ports are 232, unless you specifically have a 485 port fitted. All my 484/422 comms ( 2 & 4 wire) go through interface converters. Also note that the cable from the converter to the pc needs to be kept as short as possible, as 232 data doesn't travel over distance like 485 does.

Alan Hartwell

If a PC has a built-in serial port, it will most likely be RS-232.

You can buy an RS-485 comunications card for your PC. For example, Sealevel Products make models for all kinds of computer buses. See

Alternatively you can buy an external converter. I have used a number of converters from B&B Electronics. They make different kinds for different applications. In addition, they have a helpful technical library that explains the particulars of RS-485 and RS-232. See

Lynn at Alist

As all others have already said, most PC come only with RS-232 ports.

One can buy RS-485 add-in cards for a PC, but my experience shows using an external RS-232/485 converter GREATLY simplifies changing to a new PC or even using a notebook as a temporary replacement for the main PC.

With an internal card, you'll need to open the PC, move the card, and likely FIND where you put the stupid CD/floppy with the driver. Then there is still the small probability that the old RS-485 card or driver won't even work in the new PC. Even if it is a PCMCIA card for a
notebook there will always be the driver issue.

Having an internal RS-485 card MIGHT add hours or even DAYS to the time it takes to move an application from one computer to another.

best regards
- LynnL

I have been in a similar position and tried a number of RS232 to 485 converters but the only that worked with the moore module I had was the one manufactured by moore themselves.

Hope this helps