The AVR Mode CRC Driver:
The AVR Mode CRC and Bit Error driver is a tool that is running on the
PC and has two serial interfaces:
- First serial interface reads frames from the Mode-S Beast,
but also from all other AVR mode receivers.
- Second serial interface outputs the frames to the GUI
application, also on a serial port. At the moment PP cannot read the
data by itself, so COM0COM virtual cable must be installed and provide
the interface connection.
If the incoming data does not have CRC pre-checked in the
receiver/decoder, the bit error driver trys to correct up to to
erroneous bits in DF-11 and DF-17/18 frames so that the CRC is correct.
It also pre-checks the other frames against the valid aircraft ID, so
that the load towards the GUI is reduced.
Bit errors look like this in the signal:
Currently only F5ANN has that driver
in operation. We both see an improvement of about 20% of
DF-11/17/18 frames. This output is for example from my currently
running instance:
Date
Time Frames in out
%
immediate
1Bit
2Bit DF17/DF11#
24.03.2011
21:29:01 2606
943(36%) 453(17%)
113(25%) 62(13%) 270
24.03.2011
21:30:01 2637
951(36%) 466(17%)
122(26%) 65(14%) 276
24.03.2011
21:31:01 2611
943(36%) 457(17%)
121(26%) 61(13%) 275
24.03.2011
21:32:01 2617
955(36%) 459(17%)
117(25%) 61(13%) 276
24.03.2011
21:33:01 2608
979(37%) 457(17%)
114(25%) 61(13%) 270
24.03.2011
21:34:01 2610
987(37%) 458(17%)
114(25%) 64(13%) 266
Frames in is
the number of raw, non-CRC checked frames that I am getting from my
Mode-S Beast
out is the
total number of frames that later are sent to Planeplotter
immediate
means the number of DF-11/17/18 frames that do not have a bit error
(DF-11 includes those with interrogator ID)
1 Bit is the
number of DF-11/17/18 frames that suffer from a 1 bit error
2 Bit
is the number of DF-11/17/18 frames that suffer from a 2 bit error
DF17/11# is
the number of DF11/DF17 squittter frames that are sent to Planeplotter
(same values as ModeSCompare displays)
I am planning to release the driver as soon as it can
interface to planeplotter without the need of COM0COM.
