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[Discuss-gnuradio] Liquid DSP Flexframe and GNU Radio


From: Vanhoy, Garrett M - (gvanhoy)
Subject: [Discuss-gnuradio] Liquid DSP Flexframe and GNU Radio
Date: Tue, 26 Jul 2016 01:13:31 +0000

Hello,


I have sent this to the list once before, but I did not see it show up on the index so I am assuming it did not work after waiting some time.


I am attempting to embed the liquid DSP flexframe protocol in a custom GNU Radio block. I am doing this by extending the out-of-tree module that Tom Rondeau recently worked on. I am writing a block that embeds the flexframegen and another that embeds a flexframesync. Since these blocks tend to produce a varying amount of symbols depending on the coding scheme or modulation, I wrote it as a general block. You can see the current version of the code at my own fork.


I am currently having trouble with the generator and occasionally the sync block as well. However, for the generator, I am getting a return code -11 (I assume a seg fault) when I attempt to copy a generated frame to the out buffer and run this in GNURadioCompanion. This often happens after attempting to copy ~16000 gr_complex items to the outbuffer. Is there a problems with that amount? Here is my work function code:


    {
        unsigned int buf_len = 1000;
        unsigned int payload_len = 4096;
        unsigned char header[14]; // Liquid hardcodes this as the length for the header
        unsigned char payload[4096];

        unsigned char *in = (unsigned char *) input_items[0];
        unsigned char *inbuf = in;
        gr_complex *out = (gr_complex *) output_items[0];
        gr_complex *outbuf = (gr_complex *) malloc(buf_len*sizeof(gr_complex));
        gr_complex *front = out;
        int byte_count = 0;

        unsigned char frame_count;
        unsigned int total_items = 0;
        int frame_complete = 0;

        // Make header
        for(int i = 1; i < 14; i++) header[i] = i;
        while(byte_count < ((int) ninput_items[0]) - payload_len) {
            header[0] = frame_count;
            frame_count > 255 ? frame_count = 0 : frame_count++;
            memcpy(payload, inbuf, payload_len);
            inbuf += payload_len;
            byte_count += payload_len;
            // Assemble the frame
            while (!flexframegen_is_assembled(d_fg)) {
                flexframegen_assemble(d_fg, header, payload, payload_len);
            }

            // Make the frame in blocks
            frame_complete = 0;
            while (!frame_complete){
                frame_complete = flexframegen_write_samples(d_fg, outbuf, buf_len);
                memcpy(front, outbuf, buf_len*sizeof(gr_complex));
                front += buf_len;
                total_items += buf_len;
            }

            // Get frame length
        }

        free(outbuf);
        consume_each (total_items);

      // Tell runtime system how many output items we produced.
      return total_items;
    }


Any ideas? Thanks for any help.



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