Mariusz SP3FXC wrote:
I'm looking for some info on NRZI coding. google gives me useless links...
nothing special. I am about to write someting that uses NRZI but i can not
find any specification.

If you look at this with a monospaced font (Courier for example) it
should make sense:

__ ________ _____ __
__| |__| |__| |________|
0 0 0 1 1 0 0 1 0 1 1 0

Non-Return Zero Inverting means (1) the signal does not return
to a resting state after a bit, and (2) a zero is indicated by
a change of state, and a one by no change. Clock is extracted
from the data, which means there must be a limit to the number
of consecutive 1's, and the "zero stuffing" technique leads to
a bigger discussion.

HTH