Despite claims that it'll work with pretty much anything, the FLIRC seems to have highly erratic response to different code formats, and this totally affects how it controls the attached device - everything from properly sensing single taps or held commands, how quickly/often commands repeat when held, how frequently you can send commands, and so forth.

Most devices handle Sony codes well since they're so common and basic, and that was what I first used with the FLIRC - and it was absolutely horrible. Way worse than the buggy MCE IR receivers I'd been using.

I saw some comments that Panasonic worked well with the FLIRC - so I tried them, and the difference was night and day. It now works just as well as I'd expect an attached keyboard to work.

I mapped it using a Panasonic DVD-R codeset. URC DVD codeset #289 in specific, but it should work the same no matter what Panasonic codes you feed it... so long as they're in Panasonic format.

There might be other code formats that work as well, but once you've found one there's really no reason to keep looking. Just create a device with those codes, rename any random function to what you want it to be, and teach those to the FLIRC.