I bought notebook few days ago and of course it doesn't have serial port :) I'm interested in satellite technology and most satellite receivers use serial port for communication with computer. That's why I need serial port. Since my notebook doesn't have it, only solution is to use USB to RS232 converter. Can it completely "mimic" serial port which can be found on older PC motherboards? Are there some limitations? Best regards

  • 1
    If you really need a complete native RS232 port with all the handshaking signals, then you probably need a machine that actually has one, but if you're okay with just RX and TX, then almost any USB converter could work. – AaronD Nov 6 '15 at 22:49
  • 1
    Handshaking is conceptually simple, but the ramifications can be difficult to get right in a device with limited resources like a USB dongle. They'll probably bit-bang the handshake signals with no problems, but they may not work per the full spec. – AaronD Nov 6 '15 at 22:50
  • Well, for communication with receiver, I use null modem cable, which uses pins 2, 3 and 5. Scheme: 2-3, 3-2, 5-5. My idea is to connect USB to RS232 to notebook (USB connector), RS232 connector to one side of null modem, and second side of nullmodem to satellite receiver. Can it work on this way? – hari Nov 6 '15 at 22:55
  • 1
    @AaronD on FTDI chips all signals work above specification on all supported speeds. A well made RS232 chip actually has much more resources than a 90's bios or co-processor. Never forget the original standard is from the 70's or even before so a lot has huge margins. – Asmyldof Nov 7 '15 at 0:21

My experience has been that at least the control signals DTR/DSR and RTS/CTS are usually supported in USB to RS232 cables. Don't know whether any other seldom used pins are.

I would stick with cables using FTDI chipsets, as I know they have these four handshake signals (along with TXD and RXD):

enter image description here

This chipset even has DCD and RI, so it has all the signals present on an RS232 DB-9 connector.

There are several USB to RS-233 cables on Amazon, search for USB RS232 FT232R. Drivers are included in Windows 8 and later; you may have to download them for Windows 7 and earlier.

|improve this answer|||||
  • 2
    It's a good chip +1 – Andy aka Nov 6 '15 at 23:22
  • Thanks for answer. Here is one I ordered aliexpress.com/item/… I hope it will work :) – hari Nov 6 '15 at 23:31
  • 1
    @han I just now saw that you wanted a null modem cable. You can get one with USB to RS232 using the FTDI chipset here. I realize you already ordered a cable, in that case (if you don't want to return the other one) you can use a null modem adapter which will swap pins 2 and 3 and is also available at Amazon and other sources. – tcrosley Nov 6 '15 at 23:54
  • @ThreePhaseEel Oh I didn't see that, I'll update my answer. – tcrosley Nov 7 '15 at 2:17
  • Before FTDI chip, there were some embedded solutions 15yrs back that weren't working as integrated COM port. After FTDI, no problems was ever seen by me in using virtual COM ports. – Marko Buršič Nov 7 '15 at 9:38

Look at commercial grade USB RS232 adapters such as Edgeport by Digi, they are about 2-4 times as expensive as the cheap USB adapters, but they can give you as close to a pure RS232 experience as possible, even maintaining the same Com port regardless of the USB port they are connected to. These will also give you all signal lines including RI as well.

|improve this answer|||||

Digi Edgeport, Moxa, but also cables with FTDI chipset should offer the full handshake logic.

The problem was in the past sometimes that on the Windows driver side, more exotic things like BREAK states or "RTS On Send" (RTS_CONTROL_TOGGLE in Windows Communication API) were not supported.

In the recent years I have not run into any related issues any more.

|improve this answer|||||

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.