On Mon, Feb 27, 2012 at 10:00 AM, Ben Reynwar <b...@reynwar.net> wrote: > On Mon, Feb 27, 2012 at 7:36 AM, Jeff Hodges <jeffhodg...@gmail.com> wrote: >> Does anyone know if the QAM demodulator code is working properly? I would >> like to get a QAM demodulator working for a symbol rate of 300ksym/s. I >> don't know whether I am just using the wrong parameters or if the blocks do >> not work properly, but I am not getting the results I expect. >> >> To test the code out I am using the GRC. I have a vector source with a known >> data sequence running into the qam mod block and then the output of that >> into a QAM demod block. The output of the QAM demod is running into a Uchar >> to Float, and I am plotting the results on a WX GUI Scope. I have the exact >> same settings on both the QAM mod and demod blocks. The output I am seeing >> on the scope looks completely random. (I also tried other vector source >> data: When the input is 0x0F, repeating, the output I see is 00001010 >> repeating. But when I use 0x0E, the results are random again.) >> >> I have also tried demodulating a real QAM signal with a known data sequence, >> also to no avail. >> >> I have been working on this for about a month now and haven't had any >> success. I have examined the underlying QAM.py and generic_mod, >> generic_demod codes, and they seem to be written properly. But I am not >> getting the expected results. >> >> Any help with this problem or advice you can give will be greatly >> appreciated, and I will return the favor by helping out in any way that I >> can. >> >> Thank you very much in advance, >> >> Jeff >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > > If it's not working it's probably my fault, so I'll do some tests > myself today and get back to you. > > Cheers, > Ben
I found a bug in the xml file for the demodulator that would cause problems if you requested no gray-coding. It cause gnuradio-companion to pass an incorrect parameter name. A fix is at https://github.com/benreynwar/gnuradio/commit/e68ab8589ca235563f8c061fbb79d13793d1f21f In case that wasn't your problem I'll post an example that works for me: from gnuradio import gr, digital class qam_mod_demod(gr.top_block): def __init__(self): super(qam_mod_demod, self).__init__() src = gr.vector_source_b([1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 0]*1000) packer = gr.unpacked_to_packed_bb(1, gr.GR_MSB_FIRST) self.snk = gr.vector_sink_b() mod = digital.qam.qam_mod(constellation_points=16, mod_code="gray", differential=True, samples_per_symbol=2, excess_bw=0.35) demod = digital.qam.qam_demod(constellation_points=16, mod_code="gray", differential=True, samples_per_symbol=2, excess_bw=0.35, freq_bw=6.28/100.0, timing_bw=6.28/100.0, phase_bw=6.28/100.0) unpacker = gr.packed_to_unpacked_bb(8, gr.GR_MSB_FIRST) self.connect(src, packer, mod, demod, unpacker, self.snk) if __name__ == '__main__': qmd = qam_mod_demod() qmd.run() data = qmd.snk.data() print(data) _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
