215 lines
6.3 KiB
C++
215 lines
6.3 KiB
C++
/* -*- c++ -*- */
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/*
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* gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
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*
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* Copyright (C) 2018, Libre Space Foundation <http://librespacefoundation.org/>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <gnuradio/io_signature.h>
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#include "decoder_8b10b_impl.h"
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#include <satnogs/log.h>
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#include <gnuradio/blocks/count_bits.h>
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namespace gr
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{
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namespace satnogs
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{
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decoder_8b10b::sptr
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decoder_8b10b::make (const std::string& control_symbol,
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size_t max_frame_len)
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{
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return gnuradio::get_initial_sptr (
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new decoder_8b10b_impl (control_symbol, max_frame_len));
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}
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/*
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* The private constructor
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*/
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decoder_8b10b_impl::decoder_8b10b_impl (const std::string& control_symbol,
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size_t max_frame_len) :
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gr::sync_block ("decoder_8b10b",
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gr::io_signature::make (1, 1, sizeof(char)),
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gr::io_signature::make (0, 0, 0)),
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d_max_frame_len (max_frame_len),
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d_erasure_cnt (0),
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d_control_symbol_pos (0),
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d_control_symbol_neg (0),
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d_data_reg (0),
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d_wrong_bits (0),
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d_wrong_bits_neg (0),
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d_nwrong (0),
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d_nwrong_neg (0),
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d_word (0),
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d_word_cnt (0),
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d_state (IN_SYNC)
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{
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message_port_register_out (pmt::mp ("pdu"));
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set_output_multiple(10);
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if (!set_access_code (control_symbol)) {
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throw std::out_of_range ("control_symbol is not 10 bits");
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}
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d_8b_words = new uint8_t [d_max_frame_len / 10];
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d_erasures_indexes = new int [d_max_frame_len / 10];
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}
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/*
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* Our virtual destructor.
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*/
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decoder_8b10b_impl::~decoder_8b10b_impl ()
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{
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delete [] d_8b_words;
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delete [] d_erasures_indexes;
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}
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bool
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decoder_8b10b_impl::set_access_code (const std::string &control_symbol)
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{
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unsigned len = control_symbol.length (); // # of bytes in string
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/* if the control sequence is not 10-bit then throw exception */
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if (len != 10) {
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return false;
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}
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for (size_t i = 0; i < len; i++) {
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d_control_symbol_pos = (d_control_symbol_pos << 1)
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| (control_symbol[i] & 0x1);
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}
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d_control_symbol_neg = (~d_control_symbol_pos) & 0x3FF;
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return true;
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}
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uint8_t
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decoder_8b10b_impl::process_10b (int write_pos)
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{
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uint16_t diff_bits = 0;
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uint8_t min_pos = 0, temp_min_pos_rd = 0, min_pos_rd = 0;
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uint8_t min_dist = 11;
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uint8_t curr_dist = 0;
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size_t i = 0;
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while ((i < 256) || (min_dist > 0)) {
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diff_bits = (d_word ^ (d_lookup_8b10b[0][i])) & 0x3FF;
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curr_dist = gr::blocks::count_bits16 (diff_bits);
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if (curr_dist > 5) {
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curr_dist = 10 - curr_dist;
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temp_min_pos_rd = 1;
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}
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else {
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temp_min_pos_rd = 0;
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}
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if (curr_dist < min_dist) {
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min_dist = curr_dist;
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min_pos = i;
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min_pos_rd = temp_min_pos_rd;
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}
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i++;
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}
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/* report that there is erasure to this 10 bits */
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d_8b_words[write_pos] = min_pos;
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/* If we did not found a perfect match, mark this index as erasure */
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if(min_dist != 0) {
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d_erasures_indexes[d_erasure_cnt++] = write_pos;
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}
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}
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static inline uint16_t
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pack_10b_word(const uint8_t *in)
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{
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return ((in[0] & 0x1) << 9) | ((in[1] & 0x1) << 8)
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| ((in[2] & 0x1) << 7) | ((in[3] & 0x1) << 6)
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| ((in[4] & 0x1) << 5) | ((in[5] & 0x1) << 4)
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| ((in[6] & 0x1) << 3) | ((in[7] & 0x1) << 2)
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| ((in[8] & 0x1) << 1) | (in[9] & 0x1);
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}
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int
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decoder_8b10b_impl::work (int noutput_items,
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gr_vector_const_void_star &input_items,
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gr_vector_void_star &output_items)
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{
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int i;
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const uint8_t *in = (const uint8_t *) input_items[0];
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/* Search for the Comma symbol */
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if(d_state == IN_SYNC) {
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for (i = 0; i < noutput_items; i++) {
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d_data_reg = (d_data_reg << 1) | (in[i] & 0x1);
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d_wrong_bits = (d_data_reg ^ d_control_symbol_pos) & 0x3FF;
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d_wrong_bits_neg = (d_data_reg ^ d_control_symbol_neg) & 0x3FF;
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d_nwrong = gr::blocks::count_bits16 (d_wrong_bits);
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d_nwrong_neg = gr::blocks::count_bits16 (d_wrong_bits_neg);
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/* we found the controls symbol */
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if ((d_nwrong == 0) || (d_nwrong_neg == 0)) {
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d_erasure_cnt = 0;
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d_word_cnt = 0;
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d_state = DECODING;
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return i + 1;
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}
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}
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return noutput_items;
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}
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/*
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* From now one, we have a SYNC so we process the data
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* in chunks of 10 bits
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*/
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for(i = 0; i < noutput_items / 10; i++) {
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d_word = pack_10b_word(&in[i * 10]);
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/* Revert 10b to 8b and accumulate! */
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process_10b (d_word_cnt);
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d_word_cnt++;
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if(d_word_cnt == d_max_frame_len) {
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d_state = IN_SYNC;
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pmt::pmt_t data = pmt::init_u8vector (d_max_frame_len / 10,
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d_8b_words);
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pmt::pmt_t erasures = pmt::init_s32vector (d_erasure_cnt,
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d_erasures_indexes);
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pmt::pmt_t out = pmt::make_dict();
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pmt::dict_add(out, pmt::mp("pdu"), data);
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pmt::dict_add(out, pmt::mp("erasures"), erasures);
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message_port_pub (pmt::mp ("pdu"), out);
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return (i+1) * 10;
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}
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}
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return noutput_items;
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}
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}
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/* namespace satnogs */
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} /* namespace gr */
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