Dave Hui:
I would recommend that you find several specific pairs of IR control transmitters and receiving devices (TV, VCR, STEREO, DVD, etc etc) that use the protocols that you are interested in. Philips devices are sure bets to look since the RC5 and RC6 are their invention. Take the IR transmitter and aim it at an IR receiver you rig up on the bench. Scope out the waveform from the receiver module. Compare this with the standard RC5 and RC6 specifications (which you can find on the web if you don't have them already). From this you can deduce the exact code patterns used for various buttons to control the target device. Next you program your microcontroller to to produce an equivalent waveform (taking into account that you also need to modulate this envelope shape with a 36 KHz carrier) and feed that signal to a IR transmitter LED. If you modulate with the same pattern you should gain the ability to control the target TV, VCR, etc.

Note that RC/5 and RC/6 protocols use the 36KHz carrier as opposed to 38 KHz that is common to other protocols such as the Sony, NEC, and others.

If you want to get a better picture of what the transmitted signal looks like from an IR transmitting control, with the modulation, you can break open the control. It is possible to find the signal that either is right on the IR LED or look for the base of a transistor which is typically used to driver the IR LED. Here you can see the actual transmit waveforms without the distortion that normally you would see at the output of an IR receiver on the bench. It will be far more reliable if you duplicate the timing of the drive signal at the IR transmitter as opposed to modelling your timing from the IR receiver. This is the exact reason that cheap trainable general purpose remote controls work so crappy. They learn distortion and then try sending that distortion to the TV for example where more distortion occurs in the TV receiver. This double whammy is what makes them work less well.

There are some products with learning capability, such as the Philips Pronto (many references available from a Google search) that learn not in the normal means. The pronto actually has a high bandwidth receiver that receives the carrier and the envelope signal and then some clever internal software can figure out the carrier frequency and derive a much more reliable learned remote data set.

If you are interested in playing around with the Pronto please contact me. I have actally done some work and figured out how it's learned data bases work and then downloaded them into PC for inspection. Then it is possible to make up your own codes which you re-download to the Pronto to have it send them.

Have Fun
Michael Karas