I'm trying to find out what kind of modulation and encoding is used by my window cover remote control, aiming to implement the same on a Raspberry Pi to add a bit of home automation.
A colleague helped me sample the signal with an USRP and gave me the data files. I have examined them with Inspectrum.
I'm afraid the samples have been recorded centered very close to the frequency of the signal. I've later read that this might not be a good idea, and I think this is what causes the permanent noise you can see in the pictures. Should I center the sampling a few kHz below in the future?
Single press of the "open window" signal
Symbol rate, or rather what I guessed was the symbol rate, seems consistent at this level (around 42 bauds).
This shows frequency energy. X axis is time, Y axis is frequency (baseband). Colors have been tuned to show only the interesting power.
Detail of one of the "blocks"
Here, the last picture shows, frop to bottom: frequency, IQ (red/blue), and phase. I don't quite know what the frequency chart represents here.
Zoom on the transition between sparse to dense
The "symbol rate" doesn't seem constant here.
I have no idea what kind of modulation, encoding, bit rate, or protocol this remote uses, and right now my only option would be to blindly try all the demod blocks in gnuradio.
It'd be extra helpful if the answer could include some guidance as to how to demodulate this signal in gnuradio in order to get bits out. I think I can take it from there.
The controller is for a Velux window cover, but I haven't found any information on the web. I ultimately need to find out what chip to buy for the Arduino/rPi.
I can tell the chip has some text inscribed, but I cannot read it, seems it's worn off, but I don't have a magnifier... :/
Raw data uploaded to: https://www.dropbox.com/s/rh2k7ho68dvoxhd/data_mando3.dat?dl=0 . Sample rate is 3MHz. Data format is GNU Radio Companion default, which is IQ, each component expressed as a 32 bit float.
After some more investigation this seems to be io-homecontrol protocol. It seems it hasn't been reverse engineered, it's ciphered, and no information is available. It's a two way protocol so I'll need to grab samples from full conversations (the current samples are taken with only the remote available).
This chip in theory is able to work with this protocol: http://www.analog.com/media/en/technical-documentation/data-sheets/ADF7022_2page.pdf
The consortium will not provide specs. I'm still interested in sniffing a few conversations with GNURadio and see if I can work from them. Given this, I can only recommend against io-homecontrol and Velux products.