decode_ccsds_27_fb_impl.cc

/* -*- c++ -*- */
/*
 * Copyright 2012 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "decode_ccsds_27_fb_impl.h"
#include <gnuradio/io_signature.h>

namespace gr {
namespace fec {

decode_ccsds_27_fb::sptr decode_ccsds_27_fb::make()
{
    return gnuradio::make_block_sptr<decode_ccsds_27_fb_impl>();
}

decode_ccsds_27_fb_impl::decode_ccsds_27_fb_impl()
    : sync_decimator("decode_ccsds_27_fb",
                     io_signature::make(1, 1, sizeof(float)),
                     io_signature::make(1, 1, sizeof(char)),
                     2 * 8),
      d_count(0) // Rate 1/2 code, unpacked to packed conversion
{
    float RATE = 0.5;
    float ebn0 = 12.0;
    float esn0 = RATE * pow(10.0, ebn0 / 10.0);

    gen_met(d_mettab, 100, esn0, 0.0, 256);
    viterbi_chunks_init(d_state0);
    viterbi_chunks_init(d_state1);
}

int decode_ccsds_27_fb_impl::work(int noutput_items,
                                  gr_vector_const_void_star& input_items,
                                  gr_vector_void_star& output_items)
{
    const float* in = (const float*)input_items[0];
    unsigned char* out = (unsigned char*)output_items[0];

    for (int i = 0; i < noutput_items * 16; i++) {
        // Translate and clip [-1.0..1.0] to [28..228]
        float sample = in[i] * 100.0 + 128.0;
        if (sample > 255.0)
            sample = 255.0;
        else if (sample < 0.0)
            sample = 0.0;
        unsigned char sym = (unsigned char)(floor(sample));

        d_viterbi_in[d_count % 4] = sym;
        if ((d_count % 4) == 3) {
            // Every fourth symbol, perform butterfly operation
            viterbi_butterfly2(d_viterbi_in, d_mettab, d_state0, d_state1);

            // Every sixteenth symbol, read out a byte
            if (d_count % 16 == 11) {
                // long metric =
                viterbi_get_output(d_state0, out++);
                // printf("%li\n", *(out-1), metric);
            }
        }

        d_count++;
    }

    return noutput_items;
}

} /* namespace fec */
} /* namespace gr */