6 Dec
2013
6 Dec
'13
6:33 p.m.
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 <bistromath(a)gmail.com> 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 <fritz.meier(a)myway.de> 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
