Update all the SDR implementation to use it.
This was getting pretty ugly with code getting copy&pasted in all the SDR
implementations. Unify it all and give it a simpler API. Linked list works out
much simpler than the circular buffer. Also, simplify copying the overlap region
around by just using a separate buffer (it's only a few hundred bytes long, so
the double copy is not a big deal).
The commit provides a basic implementation of support for LimeSDR USB
receivers based on LMS7002 chip. The solution has several limitations:
- passing parameters for tune LimeSDR receiver via command-line
options is not implemented;
- only hardcoded configuration is used (channel 0 of lower band LNA,
LMS_FMT_I16 format, gain, bandwidth and timeout);
- only one device is supported and it is not possible to select a
desired one in case if several devices are connected to the host.
Test: compare the output of the program for RTL and LimeSDR receivers.
Environment:
- RTL2832SDR dongle;
- LMS7002M based USB LimeSDR board;
- 800MHz-2200MHz omnidirectional antenna with SMA connector.
Procedure:
- connect RTL dongle to the host and start the program with the
following parameters:
$ ./dump1090 --device-type rtlsdr --interactive
- wait until several planes will be detected;
- stop the program, connect the LimeSDR board to the host and restart
the program with the following parameters:
$ ./dump1090 --device-type limesdr --interactive
- ensure that the same planes are detected.
Acceptance criteria: the same planes are detected using both receivers
and track information matches with information from the
FlightRadar24 application.
Signed-off-by: Gluttton <gluttton@ukr.net>
A "reliable" message is a DF17 or DF11 with good CRC.
A "reliable" aircraft is one that's probably real - we decide it's reliable when
we've seen enough reliable messages, or just enough messages in total, that it's unlikely
to be noise.
The old matching process which tracked mode A values as pseudo-aircraft
got very, very expensive with a large number of mode A/C messages (and
with lots of single-bit errors, which seems common with a Beast doing
the reception)
Instead just count A/C messages directly into a 4096-entry array (which
is very fast) and periodically scan the mode S aircraft list to see if
we can match anything up (which is fixed overhead + cost proportional
to the number of mode S aircraft)
Oliver Jowett
Gluttton
Determinant
Carlos Pizarro
Oliver Jowett
Michael Tatarinov