due to boredom I've tried to RE simple cheap wireless ring bell which uses 433.92MHz transmitter and receiver. It sends several times the same information. On the transmitter side there is AD1614AT chip (which seems to be this one). On the receiver side there is CMT2210LC chip (this one).
I've recorded data on DOUT pin on the receiver side, it looks like following:
I'm not very familiar with such coding protocol(?) so I need help from more experienced guys here.
Data from record looks like that (assuming that 200us is our "clock"):
1110 1000 1000 1000 1000 1000 1110 1110 1000 1110 1110 1000 1110 1000 1110 1000 1000 1110 1000 1000 1110 1000 1000 1000 1000
I've noticed also that short impulse takes about 200us and long one about 600us. It looks like data is encoded as pair of long and short states, for example 600us H + 200us L -> binary "1". If we do such decoding we get following data:
10000 01101 10101 00100 10000
or if we decode data other way we have:
01111 10010 01010 11011 01111
I've grouped data into 5 "bits" because we got 25 bits in total. From that point I'm lost. Do you guys know such coding/decoding method? I saw something similar (long/short impulses) some time ago in some old IR remote control but I don't know anything more. I've checked transmitter's datasheet and in ODS_TIMING register description (page 42) I've found following "serializer" description:
ODS_GROUP_WIDTH[2:0] - Controls Symbol Group width, from 2–8 Symbols. Set to 4 to transmit 5 symbol groups obtained from 4/5 encoding. Or set to 7 to send 8 symbol group obtained from Manchester encoding of 4 bits.
With 4/5 encoding we would decode it to:
10000 01101 10101 00100 10000 -> no '10000' symbol in the table :(
01111 10010 01010 11011 01111 -> 0x07 0x08 0x04 0x0D 0x07
I'm not sure is that data has any meanings, but it would be nice to know if I decoded it correctly.
For any hint and help thanks in advance!