Bob, the narrow IrDa pulses use a pulse for every bit "1" on the RS232
interface and keep low for "0" bits, that's simple and easy, it requires
a good sync, a pulse shapper and the decoding at the receiver. There are
some standards, as the pulse width to be a percentage of the RS232
pulse, you can read more at http://www.irda.org
Wagner.

Bob Blick wrote:
>
> > Most likely what you have is the 'standard' IR (as in TV remote) signal
> > which is either 40khz (or sometimes 38khz) on-off modulation, which
> > is then further 100% (as in AND) modulated by the 'iintelligence', i.e.
> > the raw RS-232 1/0 stream. If you have a scope (sounds likely) and
>
> No. It is definitely not modulated. I used a real photodiode properly
> biased so I would be sure to see any modulation. Here's an example that
> shows the same character transmitted out a serial port and then the IR
> port:
>
> serial port:
> ---   ------   ---      ------
>    ---      ---   ------      ---
>
> IR port:
> -     -  -     -        -  -
>  ----- -- ----- -------- -- -----
>
> Sorry that was an 11 bit stream but I don't want to redraw it, both are 10
> bits per character(1 start, 8 data, 1 stop). You can see that when the
> serial port has two adjacent positive bits, the IR port sends it as two
> pulses. Chances are the IR input has at least a couple of selectable
> filters depending on the mode it's used in and the simplest one just
> filters out low frequencies, so the pulses come through fairly unscathed.
> Raw serial port data would be mangled.
>
> It's a late-model laptop without any IRDA drivers loaded, the IR port
> shows up as com3 and the terminal program seems to have no problems
> talking to it(or listening). If I take the serial out of another computer
> and AND it with a 9600 HZ pulse wave, and dump that signal into an IR
> LED I can talk to the laptop just fine as long as the 9600Hz signal is in
> phase, but since I was using a function generator the best I could get was
> working for 1 second, then bad data for a couple of seconds and so on.
>
> If no one has heard of this I'll probably write a little program that'll
> convert serial to these pulses and give it a shot. I'll let y'all know how
> it turns out.
>
> Cheers,
> Bob