I am trying to understand this protocol that my DSC 1555 alarm uses between the base and the keypad, but issue is its propriatary of some sorts. There was another thread about it on this forums but it ended prematurely with the guy just checking one bit for stay or away mode.
From what I know about this protcol so far the clock line runs at 1kHz with 50% duty and oddly enough only does so for 41.6ms then it stays high for 5.4ms and starts all over again. The data line seems to transistion on either the falling or rising edge of the clock (or in the middle), which led Kortuk of chiphacker.com to belive that it is NRZ encoding which I'm not sure of yet but here are some OLS dumps of the data and clock lines hopefully with teamwork we can figure this out.
I'm pretty sure the data is the same as whats listed in the PC5401 pdf below just sent via some weird protocol, all I really need help with is figuring out whats a 1 and whats a 0. From there I'm confident I can figure out the rest. Thanks for your time :D
0 is the Data line, 1 is the Clock