Hello, I am making good progress.
The first couple of weeks or so (months?) I was collecting information. I managed to get some design articles about Mode S transponders, various protocol specifications, and comments. I was able to decode some packets by sight using the oscilloscope program. The bit timing is very tight. Thanks go to Matt Ettus for designing a board that can handle a 4 MSPS sampling rate. It was now coding time! I reviewed some GNURadio design guidelines and how to write a module. Of course the name is most important. I decided on a subdirectory off gnuradio named gr-mode-s. gr-transponder would make it look like sending as well as receiving. My project is focused on Mode S data and derivatives (TCAS, ACAS, ADS-B, TIS-B, etc). I am open to a better name as the mode-s name forced me to use the prefix of mode_s for things. I decided to use gr-pager as the model as it is the closest to what I want to do. I eliminated some blocks but may put them back in. I basically have a slicer, decoder/framer, and parser C++ blocks. I use python code to put the blocks together into a mode S decoder superblock. I appreciate the autoconf/automake and the whole gnuradio build scheme. For a programmer who has only done small gcc projects it looks like it is real work to do things from scratch. I was able to figure out what most of the autoconf/automake files are for. I replaced the pager prefixes with mode_s, add the required .m4 files, etc. I was amazed that I got my new project integrated into the build tree quickly. The major part of the time was spent getting my code to work. So I am jumping up and down with joy as I can now decode Mode S. I can now work on improving the slicer, add decoding of the messages, etc. It seems like I am not getting hundreds of miles of range due to the antenna setup but I get enough to work on the decoders. A future to-do is to submit my code. I guess I need to join the patch list. It would be neat if I could get hardware that is smaller sized. Maybe a USRP Jr board that allows one receiver or one receiver and one transmitter board, I could also use one with a LFRX board and dedicate it to my AR5000. 73 Eric _______________________________________________ Discuss-gnuradio mailing list [EMAIL PROTECTED] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
