I know not a lot about computers and am having problems.

I have a pretty old specialist handheld computer that I'm borrowing to use with some equipment. The computer only has two ports that say "com". It looks like the thing on the right-

I need to plug a USB cable into it. There are no USB ports on the handheld thing because it's old and shite. Is "Com" the proper name for this? Is that what I should be asking for in a computer shop?

Does an adaptor that basically is like the one in the picture but has the male/female bits swapped?

Also, where can one get one on a Sunday morning? 🙄

your ****.

you should have thought of this before setting out to do field work

Jambo- the correct tool for the job broke down in the field today, so have been left a bit in the lurch (it was bodged together by my supervisor and is shite)

Try a Maplin store if you can find one in your area? next best PC World

you need a male to female DB9 adaptor cable and a RS232-USB converter like you have in that picture.

or a PC with a serial port…they do still exist…

I've got loads of them in the office but I'm not there again for over a week and thats not much help. You could try PC world or the like but I doubt they'll be much help.

Depending on the application that's reading from /writing to the com port, and / or the extent of the underlying OS's HAL you might find that the USB <-> serial adaptors don't actually do anything other than give you the right shaped holes …

Does either end expect to find a hardware based parity check of any kind I wonder?

Some serial devices have a bit of a chat right down at the hardware level, before any application / data gets involved. Mostly stuff about saying hello and sorting out how they'll communicate therein.

Doesn't sound like you have much choice tho'?

I like serial interfaces – no good for shoving 'multimedia' data around of course, but ideal for long range, robust, error free transmission of small packets of data, like auto-pilots, depth plotters, GPS signatures, AIS signatures …

Right, I've read the original question again, so ignore all of the above … 😉

If you need a full implementation of the USB connection on an old machine, you won't get it via the serial I/O, so no, the other ended verions of the above possibly aren't going to help you.

Does the handheld-computer have a PCMCIA card slot (or is it more like a Psion handheld, in that it's not got 'PC' architecture)?

If so, something like this might do the job (assuming you can then find the drivers):

OCB is right.

I don't think you will get a Serial to USB converter with a female USB plug, well i've not seen one. The cable such as the one in the pic at the top of the thread is for attaching serial port (DB9, RS232) to a computer with a USB port.

What you want is something which does the reverse, so go with the PCMCIA card slot option suggestd by OCB. Note that PCMCIA card slots are often called PCI card slots now. I believe they are one and the same, but don't quote me. Best try one out in the shop with you old PC (if it actually has a PCI/PCMCIA slot – if not, have the day off!)

PC World definitely don't have it, but I can try Maplins.

Jambo- cheers!

OCB- it does have a card slot, so that looks good, thanks.

aha. I've just found out there is a cable available that'll suit my needs (from Garmin GPSes oddly enough) perfectly. Yay!

What OCB said.

You can't go Serial > USB, but you can go USB > Serial. I suspect your Garmin cable goes the wrong way round.

If the thing you're plugging in needs USB power then you definitely won't get far with just a cable. I suspect the USB PC card thing above is your best bet (note PC card, not PCI card which is something completely different and plugs inside a desktop machine). Try it before you buy it if poss – there are several versions of PCMCIA/PC card/Cardbus slots that all look similar.

Edit – I think this may do what you need if you can get to Maplin – http://www.maplin.co.uk/Module.aspx?ModuleNo=47096&C=Froogle&U=47096&T=Module