Looks like it might be manchester encoding to me.  Look that up and see
if it matches your expectations.

-Adam

Matt wrote:

>I picked up a WebTV keyboard from eBay for $.99 with the intent of
>making an IR->PS/2 converter with a PIC as the brains, but I'm having
>a terrible time coming up with any sane way of recording and
>recognizing the IR that this keyboard sends out. It's like no remote
>control I can find and it's also not IrDA from what I can tell.
>
>I have posted shots of my scope showing the waveforms produced by
>holding down the keys 0-9 on the keyboard. The time divisions are 2ms
>on the shots for a total of about 16ms per code sent out by this
>keyboard. The URL is:
>
>http://downstairs.dyndns.org/webtv/
>
>A couple of the shots are blurry, but for the most part readable. Note
>that these shots are active low.
>
>I've tried about 3 different methods for decoding this, but none are
>particularly elegant or efficient. The best that I have come up with
>so far is putting the active pulses into 8 or so different length
>categories and only watching that, but to make at least the digits
>unique, I also had to watch the length of the gap preceding each pulse
>and put them into 2 classifications. This method is terribly
>inefficient, but at least works for the digits 0-9.
>
>Anybody ever seen an encoding like this or have any ideas of a more
>systematic way of reading this?
>
>Thanks,
>Matt Schulkind
>
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