> Note that most (all ?) IR protocols are not
> at all like the "normal" serial protocols used
> over RS232 lines. IR comunications often uses
> either Manchester coding (where a shift from
> "0" to "1" = "0" and a shift from "1" to "0"
> = "1") or PWM encoding (where a "short" puls
> could be a "0" and a "long" pulse is a "1"). The
> effect is that there is always a level shift (a
> "level" is "1"/"0", "high"/"low", "carrier"/"no
> carrier") in each bit. These codes are also known
> as "self-clocking". Another effect is that the clocks
> in the sender and recevier don't have to be
> as accurate as when running standard UART comms, since
> the receiver can adjust it's timing after each bit received.

In this particular case the purpose of the IR message is to determine
whether the unit that just sent an RF transmission is also within line of
sight of the receiver.  The IR message therefore deliberately uses several
on and off intervals each of different lengths to distinguish it from IR
transmissions from other devices that may also be in the vicinity.


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