I figured out the problem. There were two things I wasn't taking into account:
- The modulator reads bits in MSB order, which means that I should pack them the same way. - There is a bit framing problem (can be solved using packet encoder/decoder). Checked converting both sequences to bits (8 per number) and realizing one's a shifted version of the other. Cheers, Fabián On Wed, Oct 3, 2012 at 10:12 AM, Fabián Kozynski <fab...@gmail.com> wrote: It's not just an offset problem. Even though in the output file, there is a > delayed sequence, it doesn't have the right bits. As it has exactly the > same period it leads me to believe that it's just a problem of phase sync. > > > Attached is a minimal grc file. > > Cheers, > Fabián > > On Wed, Oct 3, 2012 at 12:23 AM, Ben Reynwar <b...@reynwar.net> wrote: > > On Mon, Oct 1, 2012 at 1:27 PM, Fabián Kozynski <fab...@gmail.com> wrote: >> > As sanity check I'm trying a simple flowgraph in GRC with a QAM >> mod/demod: >> > >> > Vector Source ==> Throttle ==> QAM Mod ==> QAM Demod ==> Unpacked to >> Packed >> > ==> File Sink >> > >> > The parameters in the mod/demod are as default. I also have a File Sink >> > before the mod. >> > >> > In the output I see first a bunch of zeros, then a bunch of random >> numbers >> > and after 20 or so bytes I get a sequence with the same period as the >> > original one, but different numbers. I suppose this is a problem of >> phase >> > sync. >> > >> > What's the right way to simulate a simple mod/demod? How do I add sync >> > between mod and demod? >> > >> > Thanks, >> > Fabián >> >> >> It sounds like you're comparing bytes in the two files. First thing >> that I'd check is that the two files aren't offset from each other by >> a few bits so that the bytes don't line up in the same way. >> >> If that's not the problem then email me the grc file and I'll have a look. >> >> Cheers, >> Ben >> >> > >> > _______________________________________________ >> > Discuss-gnuradio mailing list >> > Discuss-gnuradio@gnu.org >> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > >> >> >
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