OK, turns out someone beat us to it a while ago, even going so far as to reverse-engineer the cheesy crypto FLARM put in there to discourage copycats. The PHY is a Nordic nRF905 (+10dBm output), the medium access control is blind random-interval squitter with no two-way communication, and all Onera's vaunted "prediction" logic is being done in an AVR (!). Kids these days...
http://pastebin.com/8ke6jnQZ The good news is Manchester-encoded GFSK is dead simple to decode, and the known parameters of the nRF905 make it easy to write a receiver. --n On Fri, Dec 6, 2013 at 8:14 AM, Nick Foster <[email protected]> wrote: > This is a new one! Thanks for bringing it to my attention. Looks like a > voluntary, GPS-based (i.e., not secondary surveillance) system. While the > serial protocol appears to be NMEA-like, the protocol "under the hood" at > the PHY layer could be basically anything, and the FLARM consortium appears > to have elected to keep specs hidden. Reading the dataport specification > gives few insights as to the PHY layer, but at least it's good to know the > protocol has "future-proof" support for all aircraft types. > > [image: Inline image 1] > > If you record good FLARM transmissions I am happy to assist in decoding > what I can, not least because proprietary protocols were meant to be open. > =) > > --n > > > On Fri, Dec 6, 2013 at 7:58 AM, Fritz Meier <[email protected]> wrote: > >> Hi, to all >> after I've seen with RTL ADSB and DUMP1090 how ADS-B transponder data >> 1090MHz (pulse modulation) is decoded I would like to start with FLARM >> (Europe 868.2 and 868.4MHz frequency modulated). The position data of >> gliders >> (ID, latitude, longitude and altitude) are sent 1xsec in the form of >> NMEA-like records. >> I work with the BeagleBone black and have a FLARM transmitter installed >> near >> the RTL-Dongle/Antenne and may at any time start recording I/Qsamples >> with RTL_SDR. >> Thanks >> Fritz >> >> >
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