RS232/485 converter


I am looking for a RS232 to RS485 converter because I need to control with an automate 18 same devices using only the RS232. For me, it means I will need 18 inputs one for each devices. So, converting all in RS485 will permits to have only one input of my automate.

I see the product IC232485S. If I well understand, I need to buy one for each instrument, in order to have a RS485 network instead of 18 RS232 communication.

Is that it ?

If yes, I imagine I will set an adress for each converter in order to select which equipment I will communicate. Right ?

tThank you in advance. Best regards.

Hello @Mathieu!

Thank you for your post!

I was able to take some time to look into the support we offer for the IC232485S and we have it listed for bidirectional use with RS232 and RS485 support. So I would certainly expect it to work fine with individual devices. We do not have support information for use with multiple devices. I am sorry about that!

StarTech RS232 to 422/485 Converter

Mfg.part: IC232485S


However, I will note that the IC232485S includes jumpers. When I dug a bit deeper I do see that we had a note about these: “This RS-232 to RS-422/485 Converter equips independent TX&RX and RTS&CTS termination resistors for RS-422/485 connector. The user can modify jumper settings (short the pins) to avoid impedance mismatch problems when operate under Multi-drop transmission.”

This does imply that a multi-drop configuration may be possible but I do not have setup and support information for that.

If you are looking to support multiple RS232 devices our best solution with the highest number of RS232 ports will be:

StarTech 16 Port USB Serial Adapter

Mfg.part: ICUSB23216FD


I’ll check back on this post for any replies and I will be happy to look into this some more, or make other recommendations.

You are welcome to post more details too, this might help me better understand what you wish to achieve.

Thanks again!



Thank you for your answers. I think we will try with two converters like this and if is not working I will use your second solution. In my luck, I have 18 devices and your system has 16 inputs ^^

Thank you again.

Best regards.

Hello @Mathieu

I am glad that I could help!

Of course, it’s too bad we do not have a USB to RS232 adapter with more ports.

We do have a 2 port version that you could add in:

2 Port Industrial Wall Mountable USB to Serial Adapter Hub with DIN Rail Clips

Mfg.part: ICUSB2322I

2 Port USB 2.0 to Serial Adapter Hub - Serial Cards & Adapters

4 ports, if you are curious: 4Pt USB Serial Adapter

Mfg.part: ICUSB2324I

4 Port USB to DB9 RS232 Serial Adapter - Serial Cards & Adapters

I would be curious to know how the IC232485S tests out for you too.



Hello again,

I think about that topic this weekend, and I was wondering how works these rs232 to usb converter. If we plug two of them on a computer, will we be able to control the rs232 devices from our C++ code through something like a SDK of the converter ?

Thank you in advance. I search for all possiblities before to launch the buy and test. Best regards.

Hello Mathieu,

Once connected to a USB port on a computer with drivers installed the ICUSB23216FD, or other USB to serial adapters, will show up with COM ports or serial interfaces. This might vary a bit depending on your operating system.

RS-232 communication is very standardized, and while does not have specific support for C++ or have an SDK, I should certainly expect that that there are libraries available for serial communications. Once you have a C++ library imported it should allow you to control the serial devices. Sadly, I am not very familiar with C++ so I do not have any recommendations.

I hope that this information will at least point you in the right direction!

Thank you for this information. I think we need to buy one converter (with 2 inputs for example) and see how it works in details. Have a good day. Best regards.