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Hello - I'm poking around with a Visonic door sensor, trying to figure out the protocol it sends out over 868 MHz.

What I can see is a very clear pattern of 001/011/101/111 transmit on/off transitions with all pulses either 80 or 160 µS (approx).

When you take out the fixed 1's, you end up with 36x2 = 72 bits:
_-__-_--__--_-_-__-_--_-__--_-_-__--_-__--__-_--__--__-_--_-__-_--_-__--

Probably a header / preamble, the payload, and then a checksum/trailer.

But what is what? Does anyone have more information about the bit allocations used for these packets? I haven't found anything on the web.

(I'm not interested in the secure PowerMax "rolling-code" encoding, just simple home stuff such as this door sensor)

Some corrections and progress: the pulses are 400 and 800 µs, using Manchester encoding, with a packet size of 44 .. 46 bits. Packets are sent 3 times within 2..3 seconds.

I've got a JeeNode (ATmega328 with RF) reliably decoding these packets, but preamble, byte order, bit allocation, and checksum are still unknown.

No responses and replies yet - how surprising!

For future viewers of this thread: please email me at jcw@equi4.com if you have any tips re. Visonic. I'd be interested to add it to the protocols already supported at www.jeelabs.org - so far, that includes the whole range of FS20 devices, KAKU, and (K)S300 weather station sensors.

I guess it has something to do with a lot of people already using RFXCom or visonic receivers, which at least in the first case already do the decoding. So there's not really a need to re-invent the wheel.
I encourage you to keep at it however, Jeenodes seem to promising parts and I'm thinking about using them for a irrigation thingie.
Maybe B_weijenberg can give you some tips or pointers where to get the info, he's active on this forum and others.

Thanks, good point. Main reason for doing this, is because I've already got the entire infra-structure in place for receiving and sending 433 & 868 MHz signals. Many Visonic sensors have FS20 equivalents, so it's no big deal for me, but it'd be fun to add - and since what I do is open source, it might be of use for a slightly different audience.