Before I bought my XT (but when I was planning on getting one) I knew I'd need a monitor for it. Fortunately for me, the region I was living in had recently transitioned from analog to digital TV signals, so a lot of people were disposing of TVs that were perfectly good apart from not having a built in ATSC decoder. So I didn't have to walk past very many yard sales before I found an ideal little 13" Orion TV1334A. The only downside was that it didn't have a remote control, which I discovered that I needed to change the brightness and contrast (without changing the brightness and contrast, the old-style CGA has rather poor composite output). I tried to make a fake remote using an Arduino, an IR LED that I pulled out of an old DVD remote, IRemote and LIRC's remotes database, but unfortunately I found that the latter did not contain codes for the TV1334A.
Fortunately I was able to find a suitable remote on eBay for a reasonable price (albeit still slightly more than I paid for the TV, which annoys me slightly). If I had just done that to start with that would probably be the end of it, but now that I've gone to the trouble of writing some IR code for the Arduino I want to be able to use it! This isn't as useless as it might sound, because it would be nice to be able to control the TV from the computer - to turn it on from another room, run a CGA program remotely, view the result over a webcam and then turn it off again.
Can't you hook up an IR-to-serial receiver and use that to capture what the remote's codes are? After all, there are plenty of learning remotes out there (I have a couple at work which do an admirable job), and although IR-serial (or IR-USB) transceivers aren't exactly junk-price, they are fairly inexpensive. And there are lots of oldish laptops that will have one built in (much like my own, which was made near the start of the Centrino era when it wasn't certain whether Bluetooth and Wifi would actually catch on...)
And if you can program the Arduino to *produce* IR signals, well... :)
I could certainly buy something to capture the remote codes, but I hate buying gadgets that I can make myself! I actually came across an even easier way to do it recently - http://windytan.blogspot.co.uk/2013/01/the-infrared-impulse.html .
However, lately I've mostly had my XT connected to a video capture card instead of a TV, so I never finished the remote project.
I sorta know how you feel, but when the remote in question can bought quite cheaply (I ordered a couple of 8-device ones for work in order to serve as backup for a load of different projectors etc where the remotes keep walking away ... those were £15 each, but models with fewer memory banks were cheaper still) it's kind of stretching the point a bit. How much are you willing to spend on discrete components and how much time are you willing to put in to avoid buying a commercial product that's worth less than 3 hours of minimum wage labouring?
Anyway, my question was in fact wondering why it wasn't possible to capture codes with your own kit, instead of trying to "discover" them or hunt them out another way, when commercial remotes can do it easily enough ;) ... 2-way infrared-to-serial-header doodads are pretty cheap if you go to the right places (...the wrong places will charge £10+ just for the tranceiver)
Bizarrely I actually have a couple of those IR beads hanging around here, too - I think they must have come either from someone's long-since-dead VC card, or are spares from a pro room control system - but I have no idea what we could use them for. There's not much they can connect to as-is, and the whole "run it through a sound card" thing would be a fun project but impractical for any real application, especially as you'd then need a bespoke program to receive and interpret the data and do something with it.
Maybe it could be used to set up line-of-sight wireless communication between a pair of Sinclair Spectrums or the like?
I didn't buy any discrete components for this - I had all that stuff lying around anyway. But the other side of is just that I find doing this sort of thing to be a lot of fun! If I needed to do it and the hard way wasn't fun, I'd certainly spend a few pounds to do it the easy way.
I did actually try a universal remote first, but didn't have any success with it - perhaps that universal remote also got its codes from the LIRC database.
IR serial between Spectrums would certainly be a fun hack!