A friend of mine needs a pc with an RS232 port because he needs to program some audio component which is already of significant age. Now, of course his PC doesn't have an RS232 port anymore, so he got one of though USB to serial converter. Unfortunately, it doesn't work. The software of the audio component keeps searching for a COM port, and never finds one.

I know these types of converters come a dime a dozen, but not all are equally good. Could you guys point be to a good model, one which truely acts as a good old COM port? (preferably maybe with hands-on experience?) I know this is a question which comes by every so often, but I just want to make sure I advise a good one to my friend, with good drivers etc...

Thanks!

We use the "keyspan usa19h", $25 at Amazon US, €34 at your local Amazon.

Hi.

My experience has been that for true COM port compatibility you want to find a USB adapter based on one of the FTDI chips, such as the FT232H. Make sure you install the VCP drivers as well, not the DLL ones.

They're the only USB-RS232 converters I have used that really work with everything. The Prolific PL2303 ones aren't too bad although driver support can be problematic, but the FTDI ones are rock solid even at high speeds. They do tend to be the most expensive though.


Here, for example, are a number of different ones.

pca

very nice, thanks! Unfortunately, Amazon refuses to ship it to Belgium for some reason... Oh well, I can always try eBay.

Hi PCA, and thanks for the link. Cost is not all that important, my friend only wants to be 100% sure that it'll work.
The ones you linked to, are those all FTDI ones? The cost seems very reasonable!
Cheers!

Edit: Dammit! Amazon AGAIN refuses to ship this adapter (in this case the Startech.com adapter) to my address in Belgium! Why is that? Are these things dangerous for some reason?

I've also had good luck using the FTDI adapters with difficult applications.

Hi.

Here's one on ebay.co.uk

pca

I figured ebay would be my best bet. I'll have a look, thanks!

Is it Amazon that is refusing, or the individual seller? I've had that issue with the Amazon UK sellers not shipping to Ireland, but anything that was owned and shipped by Amazon themselves was fine.

I tried Amazon UK, Amazon Germany and Amazon France. All of them refused to ship. No idea why.

Prolific PL2303 and FTDI are certainly the most common ones, and there is a lot of support out there for them, and they tend to be pretty solid. Prolific PL2303 is our Gold Standard here. (My current job is getting quite intimate with these drivers lately.) Support for Proliific is best if you go to the Prolific web site and grab their driver set, instead of relying on whatever came with your dongle.

Interestingly, the older Prolific PL2303 units have had their Windows support dropped, and you have to get one of the newer Prolific chipset revisions in order to work with Windows 8 and later. Here's the relevant quote from the README.TXT that comes with the prolific driver:




The mentioned CheckChipVersion tool is either included in the driver package, or available from the same place you download the driver package, I don't remember which.

Oooo. Might be able to help your friend here.

Sometimes older software doesn't bother searching for COM ports above COM9. If the adapter's COM port number is higher than COM9, see if you can edit it down to a lower com port number, see if the audio software detects it at that point.

Ah! Good point, didn't know that! I'll make sure to tell him! Thanks!

Also recommend FTDI based devices for your best chance and keeping the COM port low. If possible even down to COM1-4. FTDI is easily changeable but so are many others. Sometimes you have to juggle things around though since the lower ports are occupied by Bluetooth devices among other things.

If the software is so old and primitive and is hitting the hardware directly in a "DOS" window, you might have bigger problems but I seem to remember experiencing Windows properly intercepting that somehow.

Yes, COM ports are still handled correctly in DOS Windows in my experience. For instance, I was recently able to run a very old DOS-only configuration app for an old Trimble trunk-mounted GPS system.