AVR-Chat

First I want to thank everyone for their help with the software SPI, I
managed to interface with the HM55B compass successfully. For that
solution, I ended up just writing shiftin/shiftout routines. If anyone
wants to see my code it is here:
http://docwiki.gumstix.org/Robostix_and_HM55B_Compass

I now am trying to interface with the following I/R distance sensor:
http://www.hvwtech.com/products_view.asp?ProductID=91

It has a synchronous protocol that I've already bit-banged in similar
fashion to the compass. This works ok, but I'd like to try and get the
asynchronous protocol working. Essentially the sensor will
continuously send out a sync pattern byte (10101010) and then the
reading byte. The example is written in pbasic and essentially
performs a SERIN at 4800 bps with a wait on the sync pattern.

My question is this: Is there example code out there for a C
implementation of SERIN and SEROUT? I see these "bit-bang" functions
all over the place in pbasic examples and would like a C equivalent.

SERIN: As a guess I would think I could start polling the pin for the
first low-high transition and then spin (according to my processor's
clock) for the appropriate time for the specified baud (4800). In this
fashion I could start looking for the sync pattern, restarting my
search if the pattern is incomplete. I would probably need to find the
pattern twice (with a byte between) before I could be certain I've
found it. Then I can just read the next eight bits. 

SEROUT: This would be the easy part, since I can just push out my bits
based upon the baud timing. If there needs to be a sync pattern, then
I just send it first.

In each case, I would need to account for MSB or LSB.

Any thoughts from the group? Thanks in advance...