If anyone wants to keep the conversation going ( instead of receiving dozens of emails :P ) I've posted the question on reddit http://www.reddit.com/r/sdr/comments/331jeq/q_how_do_i_demodulate_a_series_of_magnitudes_in/
2015-04-18 18:44 GMT+03:00 evilsocket <[email protected]>: > Yeah as long as I know, NFC-A is modulated on ASK 100% from the reader > side and ASK 10% from the tag side, so using only one type of demodulation > I should be able to see only the reader data and wrongly demodulated tag > data ... but once I'll be able to correctly demodulate the reader side, > I'll "follow" the protocol and know what should be demodulated how .... > hopefully :P > > I'm pretty sure it's ISO14443a, at least that's what the nfc reader app > I'm using is saying. > > 2015-04-18 17:46 GMT+03:00 Martin Holst Swende <[email protected]>: > >> On 2015-04-18 16:10, evilsocket wrote: >> >> I think this is a great goal, but have you considered using GNU Radio >> >> to confirm that it works and then rewrite it in C/C++ piece by piece? >> > >> > Yep but in that case would be copying, not understanding, wouldn't it? >> :D >> > >> >> Have you looked at the waveform to see if you can identify where the >> >> data is being transmitted? >> > >> > Yep, I'm on the right frequency and it's clearly ASK. >> > >> >> I think you're on the right track. >> > >> > Great! :D >> >> One thing that will bite you with this approach, is that you'll only get >> reader-side of the comms this way. The reader does OOK, but the tag does >> not transmit; it modulates the reader signal. So, depending on whether >> the tag coil is open or closed, it will dampen or not dampen the >> reader-signal. So you'll need to have some more levels to discern these >> pretty small variations in the signal. >> >> >> > >> >> It probably depends on what is being transferred. A good place to >> >> start would be these specs: >> >> http://members.nfc-forum.org/specs/spec_list/ >> > >> > Thanks so much :) >> >> Obviously, depending on what you're observing, it will vary, but I would >> guess that the traffic you're seeing is iso14443a, afaik the most >> commonly used. The documents you're looking for would be the ISO 14443a >> specs. There are four of them: >> >> 1. Physical characteristics >> 2. Radio frequency power and signal interface >> 3. Initialization and anticollision >> 4. Transmission protocol. >> >> Start with 2, and work your way up... I can email them to you off-list >> if you'd like, shoot me an email in that case. >> >> Otherwise, it's probably iso15693 you're seeing. That's more common in >> vicinity (as opposed to "proximity") cards which can be read over a >> greater distance, e.g. ski passes. >> >> Good luck >> /Martin >> > > > > -- > > > > _________________________ > Simone '*evilsocket*' Margaritelli > http://www.evilsocket.net/ <http://www.evilsocket.net/> > -- _________________________ Simone '*evilsocket*' Margaritelli http://www.evilsocket.net/ <http://www.evilsocket.net/>
_______________________________________________ HackRF-dev mailing list [email protected] https://pairlist9.pair.net/mailman/listinfo/hackrf-dev
