Please Note: I am NOT talking about a converter that allows a serial device to attach to a USB port on my computer! Those are a dime a dozen, or five or ten bucks each. I’m talking about adding a USB port to a computer’s serial or parallel port. Many of my computers are older than some of the people here and have neither USB ports nor slots to add one to but I want to take advantage of all the wonderful USB-ported products out there. Does such an animal exist? Everywhere I look I find the ones that go the other way.
No. It’s quite hard to search for such devices, mainly because you’ll find people calling the common device (the one you mentioned - that plugs into USB and gives you a new serial and/or parallel port) either a USB-to-serial(/parallel) or serial(/parallel)-to-USB adapter (neither term is wrong, because serial and parallel ports are bidirectional and it just depends on whether you’re looking at it from the computer or the device end.
But no; I say with a fair degree of confidence that there is no such animal as a device that plugs into a serial port to provide a new USB port to legacy computers; quite apart from anything else, drivers and bandwidth would be an issue.
There are USB print servers that plug into a network, so I suppose you could plug them directly into the computer using a crossover cable (that bit is quite important), but again, I’m not sure what devices besides printers they support and whether you’d get drivers (for the device and for the USB printer server) for a machine that was old enough not to have hardware USB ports.
If your computer has a spare PCI slot, you can buy a USB adapter to go in it and they cost peanuts, but you’ll need to make sure that your OS is supported (not NT, not really Win95)
Thanks. I’ve moved on. Now I’m looking into serial to IrDA devices.
Then again, I really should be working.
Me too, oddly; let me know what you find…
I already have an USB-IrDA on my main computer at home (I don’t live ENTIRELY in the 80s) but since I don’t have admin privileges at work I can’t set it up there. Some of my things have built-in IrDA so they are set. I’ll pick up a cheap serial-IrDa on eBay and if it works on my TRS-80 Model 100 I’ll have the first “Model T” with infrared I/O capability. Then I strip the guts out of the adapter and install it inside the Model T and goodbye null modem cables!
I’ll be very interested to hear about your results; I’m trying to interface an IRCOMM (but otherwise serial) device to a microncontroller; as I understand it, some of the IR protocols fully emulate an RS232 port - that is to say that some serial-port IR adapters behave like a serial cable, as far as the pinouts, timing, and signals at each end of the link are concerned, so it ought to be possible to do it. Please post back with your results!
One serial IrDA adapter I looked at claims you can use it for standard serial communication but only between it and another for some reason. I’ll keep you posted as I learn more.
Be aware that there are a multitude of IR protocols out there; some of this might not matter, since the IR is just the bit that happens between the devices - if the hardware itself behaves like an RS232 port at both ends, you’re laughing.
I’m not familiar with the workings of the TRS-80, so I’ll just mention something you’re probably already aware of, or that is perhaps irrelevant; beware of interfacing RS232 to serial ports that are expecting signals at logic levels; RS232 uses higher voltages and can fry logic chips quite readily if it is connected directly.
There’s also this - if I’m understanding it correctically, SIR is a direct transfer of ordinary serial data over infrared instead of wires; if that’s right, one of these chaps (and not a lot else, except probably a MAX232 signal level converter or similar) should turn a wired serial port into a Serial infrared port. Surely it can’t be that simple?
Ah, but you assume, wrongly, that I know what I’m doing! All I know how to do is solder and Google and hope things don’t catch fire, though my limitations haven’t stopped me before.
(Googling) Shit! Do I have to write my own driver? That ain’t gonna happen. This bears further looking.
Interesting, but expensive at $165. 
But not nearly so expensive on eBay with an opening bid of $14.99 for an ACTiSYS ACT-IR100SL. 
astro, you are a god! And to think for your search string you tossed in the TRS-80 to see if somebody had already done this. :smack: