One more comment:
If you have a JP1.2 or JP1.3 remote and also a USB to TTL breakout adapter
/ cable to talk to a 6-pin connector on a *duino, then you should not need
any additional hardware to program your JP1.2/1.3 remote. You just have to
connect pins from the adapter to appropriate pins on the 6-pin JP1.x cable.
Unfortunately, I did not fully realize this until after I had built, debugged, and
used serial-to-JP1.2/1.3 hardware and thus have not tried out this route.
I suggest that you check the JP1 sites for details.
Programming the old JP1 remotes would still require an Arduino loaded with the
sketch above in order to directly program the EEPROM chip. In the newer JP1.x
remotes, this is accomplished via talking through the serial (TTL) interface to the
processor in the remote.