169 lines
4.5 KiB
C++
169 lines
4.5 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 "lrpt_decoder_impl.h"
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#include <satnogs/log.h>
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#include <satnogs/utils.h>
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#include <satnogs/libfec/fec.h>
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namespace gr {
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namespace satnogs {
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lrpt_decoder::sptr
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lrpt_decoder::make()
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{
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return gnuradio::get_initial_sptr(new lrpt_decoder_impl());
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}
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/*
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* The private constructor
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*/
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lrpt_decoder_impl::lrpt_decoder_impl()
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: gr::block("lrpt_decoder",
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gr::io_signature::make(0, 0, 0),
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gr::io_signature::make(0, 0, 0)),
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/*
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* Metop violates the standard as many times as possible...
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* The frame should contain 128 RS check symbols at the end.
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* For some unknown reasons, it seems that the RS encoding is not performed.
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* Thus, they dropped the check symbols at the end of the frame.
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*/
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d_cadu_len(1020 + 4 - 128),
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d_coded_cadu_len(1020 * 2 + 4 * 2 - 128 * 2),
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d_mpdu_max_len(59400),
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d_scrambler(0x2A9, 0xFF, 7),
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d_have_mpdu(false)
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{
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message_port_register_in(pmt::mp("cadu"));
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message_port_register_out(pmt::mp("frame"));
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set_msg_handler(
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pmt::mp("cadu"),
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boost::bind(&lrpt_decoder_impl::decode, this, _1));
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d_vt = create_viterbi27(d_cadu_len * 8);
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if (!d_vt) {
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throw std::runtime_error("lrpt_decoder: Failed to init Viterbi decoder");
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}
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int polys[2] = {0x4f, 0x6d};
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set_viterbi27_polynomial(polys);
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d_cadu = new uint8_t[d_cadu_len];
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d_coded_cadu_syms = new uint8_t[d_coded_cadu_len * 8];
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d_mpdu = new uint8_t[d_mpdu_max_len];
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}
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/*
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* Our virtual destructor.
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*/
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lrpt_decoder_impl::~lrpt_decoder_impl()
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{
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delete [] d_cadu;
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delete [] d_coded_cadu_syms;
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delete [] d_mpdu;
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}
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void
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lrpt_decoder_impl::decode(pmt::pmt_t m)
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{
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const uint8_t *coded_cadu = (const uint8_t *)pmt::blob_data(m);
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if (pmt::blob_length(m) != d_coded_cadu_len) {
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LOG_ERROR("Wrong CADU size");
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return;
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}
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init_viterbi27(d_vt, 0);
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for (size_t i = 0; i < d_coded_cadu_len; i++) {
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d_coded_cadu_syms[i * 8] = 0xFF * (coded_cadu[i] >> 7);
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d_coded_cadu_syms[i * 8 + 1] = 0xFF * ((coded_cadu[i] >> 6) & 0x1);
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d_coded_cadu_syms[i * 8 + 2] = 0xFF * ((coded_cadu[i] >> 5) & 0x1);
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d_coded_cadu_syms[i * 8 + 3] = 0xFF * ((coded_cadu[i] >> 4) & 0x1);
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d_coded_cadu_syms[i * 8 + 4] = 0xFF * ((coded_cadu[i] >> 3) & 0x1);
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d_coded_cadu_syms[i * 8 + 5] = 0xFF * ((coded_cadu[i] >> 2) & 0x1);
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d_coded_cadu_syms[i * 8 + 6] = 0xFF * ((coded_cadu[i] >> 1) & 0x1);
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d_coded_cadu_syms[i * 8 + 7] = 0xFF * ((coded_cadu[i] & 0x1));
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}
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/* Convolutional decoding */
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update_viterbi27_blk(d_vt, d_coded_cadu_syms, d_cadu_len * 8);
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chainback_viterbi27(d_vt, d_cadu, d_cadu_len * 8, 0);
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/* Descrambling */
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d_scrambler.reset();
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d_scrambler.descramble(d_cadu + 4, d_cadu + 4, d_cadu_len - 4, true);
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decode_ccsds_packet(d_cadu + 4);
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}
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void
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lrpt_decoder_impl::decode_ccsds_packet(const uint8_t *cvcdu)
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{
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/* Check first the VCDU version and if encryption is off */
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if ((cvcdu[0] >> 6) != 0x1) {
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return;
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}
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if (cvcdu[6] != 0x0 || cvcdu[7] != 0x0) {
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return;
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}
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/* Check if the VCDU contans data */
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//if((cvcdu[8] >> 3) != 0x0 && (cvcdu[8] >> 3) != 0x1f) {
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// return;
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//}
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const uint8_t *mpdu = cvcdu + 10;
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/* Check CCSDS packet version and type */
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//if( (mpdu[0] >> 5) != 0x0) {
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// return;
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// }
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uint32_t vcdu_seq = 0;
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vcdu_seq = cvcdu[2];
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vcdu_seq = (vcdu_seq << 8) | cvcdu[3];
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vcdu_seq = (vcdu_seq << 8) | cvcdu[4];
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uint16_t hdr_ptr = 0;
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hdr_ptr = cvcdu[8] & 0x7;
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hdr_ptr = (hdr_ptr << 8) | cvcdu[9];
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/* Try to find the start of a MPDU */
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if (!d_have_mpdu) {
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if (hdr_ptr != 0) {
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return;
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}
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d_have_mpdu = true;
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}
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message_port_pub(pmt::mp("frame"), pmt::make_blob(cvcdu, d_cadu_len - 4));
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}
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} /* namespace satnogs */
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} /* namespace gr */
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