AVR-Chat

Here's a problem I have that maybe some of the gurus on this list can
help with...

I'm just starting on a project which requires decoding of a rather
unusual AFSK bitstream and am seeking some ideas/opinions on the best
way to do it with an AVR chip (most likely ATMega88 or 168).

Each bit is equal length of 2100 microseconds (usec.) and consists of
either 4 cycles each 525 usec. long (for a 1 bit) or 3 cycles each 700
usec. long (for a 0 bit).  Frequencywise, this figures out to be
approximately 1904.8 Hz and 1428.6 Hz.  This is a synchronous format
with no start/stop bits to the 8 bit bytes being sent.  There are no
provisions or restrictions on the number of same bits in a row which may
be sent.  Some (a fairly good number of them) sync bytes are sent
initially.  The total data string could be several hundred bytes long,
so while the 2100 usec. bit length is pretty accurate, care must be
taken to account for slight inaccuracy without depending on further sync
pulses in the message.

To further complicate matters, unfortunately noise free operation cannot
be assumed as there may be some unexpected glitches come through. This
is not a format I'd chose for transferring data, but I'm stuck with it.

My initial thoughts are to try to time each pulse (cycle) to determine
the bit ( 1 or 0 ) and to count the number of cycles so to figure out
where one bit starts and ends.  In case of noise impulses, the length of
the pulse/cycle will be less than anticipated value and could probably
be discounted as long as there was another timer going which would
anticipate the end of the bit time.  Not sure I'm making myself clear on
this.

I'm certainly open to other thoughts on the matter.  Maybe this is not
too unlike trying to decode barcode stuff (Dave VH?) and I should see
what goes on there.

Anyone?

Regards,
Don