2016-07-01 23:18:44 +02:00
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/* -*- 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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2017-07-29 22:51:06 +02:00
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* Copyright (C) 2016, 2017
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* Libre Space Foundation <http://librespacefoundation.org/>
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2016-07-01 23:18:44 +02:00
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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 <satnogs/log.h>
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#include <satnogs/ax25.h>
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#include "ax25_decoder_bm_impl.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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ax25_decoder_bm::sptr
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ax25_decoder_bm::make (const std::string& addr, uint8_t ssid, bool promisc,
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2017-07-29 22:51:06 +02:00
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bool descramble, size_t max_frame_len,
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size_t n_sync_flags)
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2016-07-01 23:18:44 +02:00
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{
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return gnuradio::get_initial_sptr (
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2017-07-29 22:51:06 +02:00
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new ax25_decoder_bm_impl (addr, ssid, promisc, descramble,
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max_frame_len, n_sync_flags));
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2016-07-01 23:18:44 +02:00
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}
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/*
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* The private constructor
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*/
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ax25_decoder_bm_impl::ax25_decoder_bm_impl (const std::string& addr,
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2017-07-29 22:51:06 +02:00
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uint8_t ssid, bool promisc,
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bool descramble,
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size_t max_frame_len,
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size_t n_sync_flags) :
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gr::sync_block ("ax25_decoder_bm",
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gr::io_signature::make (1, 1, sizeof(uint8_t)),
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gr::io_signature::make (0, 0, 0)),
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d_promisc (promisc),
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d_descramble (descramble),
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d_max_frame_len (max_frame_len),
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d_sync_flags_thr (n_sync_flags - 1),
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d_state (NO_SYNC),
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d_shift_reg (0x0),
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d_dec_b (0x0),
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d_prev_bit_nrzi (0),
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d_received_bytes (0),
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d_sync_received (0),
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d_decoded_bits (0),
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d_lfsr (0x21, 0x0, 16),
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d_frame_buffer (
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new uint8_t[max_frame_len + AX25_MAX_ADDR_LEN
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+ AX25_MAX_CTRL_LEN + sizeof(uint16_t)])
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2016-07-01 23:18:44 +02:00
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{
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/* Valid PDUs output message port */
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message_port_register_out (pmt::mp ("pdu"));
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/*
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* Valid invalid (wrong CRC, different destination Callsign/SSID,
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* wrong frame size)PDUs output message port
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*/
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message_port_register_out (pmt::mp ("failed_pdu"));
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}
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void
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ax25_decoder_bm_impl::descramble_and_decode (const uint8_t* in,
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2017-07-29 22:51:06 +02:00
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size_t nitems)
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2016-07-01 23:18:44 +02:00
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{
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size_t i;
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uint8_t descr_bit;
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uint8_t dec_bit;
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2017-07-29 22:51:06 +02:00
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for (i = 0; i < nitems; i++) {
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/* Descramble the input bit */
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descr_bit = d_lfsr.next_bit_descramble (in[i]);
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2016-07-01 23:18:44 +02:00
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2017-07-29 22:51:06 +02:00
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/* Perform NRZI decoding */
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dec_bit = (~((descr_bit - d_prev_bit_nrzi) % 2)) & 0x1;
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d_prev_bit_nrzi = descr_bit;
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2016-07-01 23:18:44 +02:00
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2017-07-29 22:51:06 +02:00
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/* In AX.25 the LS bit is sent first */
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d_shift_reg = (d_shift_reg >> 1) | (dec_bit << 7);
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d_dec_b = (d_dec_b >> 1) | (dec_bit << 7);
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2016-07-07 16:57:06 +02:00
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2017-07-29 22:51:06 +02:00
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switch (d_state)
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{
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case NO_SYNC:
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if (d_shift_reg == AX25_SYNC_FLAG) {
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enter_sync_state ();
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}
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break;
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case IN_SYNC:
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d_decoded_bits++;
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if (d_decoded_bits == 8) {
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d_received_bytes++;
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d_decoded_bits = 0;
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if (d_shift_reg == AX25_SYNC_FLAG) {
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d_sync_received++;
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if (d_sync_received > d_sync_flags_thr) {
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enter_decoding_state ();
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}
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}
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if (d_received_bytes > 3) {
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reset_state ();
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}
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}
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break;
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case DECODING:
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/*
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* If the received byte was an AX.25 sync flag, there are two
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* possibilities. Either it was the end of frame or just a repeat of the
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* preamble.
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*
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* Also in case in error at the preamble, the G3RUH polynomial should
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* re-sync after 3 repetitions of the SYNC flag. For this reason we demand
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* that the distance between the last SYNC flag is greater than 3 bytes
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*/
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if (d_shift_reg == AX25_SYNC_FLAG) {
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if (d_received_bytes < 3) {
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enter_sync_state ();
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}
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else {
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/* Frame end */
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enter_frame_end ();
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}
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}
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else if ((d_shift_reg & 0xfc) == 0x7c) {
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/*This was a stuffed bit */
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d_dec_b <<= 1;
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}
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else if ((d_shift_reg & 0xfe) == 0xfe) {
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/*This can never happen... Error! */
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if (d_received_bytes > AX25_MIN_ADDR_LEN) {
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message_port_pub (
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pmt::mp ("failed_pdu"),
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pmt::make_blob (d_frame_buffer, d_received_bytes));
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}
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reset_state ();
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}
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else {
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d_decoded_bits++;
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if (d_decoded_bits == 8) {
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d_frame_buffer[d_received_bytes++] = d_dec_b;
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d_decoded_bits = 0;
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2016-07-01 23:18:44 +02:00
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2017-07-29 22:51:06 +02:00
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/*Check if the frame limit was reached */
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if (d_received_bytes >= d_max_frame_len) {
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LOG_WARN("Wrong size");
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message_port_pub (
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pmt::mp ("failed_pdu"),
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pmt::make_blob (d_frame_buffer, d_max_frame_len));
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reset_state ();
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}
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}
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}
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break;
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case FRAME_END:
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if (d_shift_reg == AX25_SYNC_FLAG) {
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d_dec_b = 0;
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d_decoded_bits = 0;
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d_received_bytes = 0;
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d_state = FRAME_END;
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}
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else {
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d_decoded_bits++;
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if (d_decoded_bits / 8 > 3) {
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reset_state ();
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}
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}
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break;
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default:
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LOG_ERROR("Invalid decoding state");
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}
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2016-07-01 23:18:44 +02:00
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}
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}
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void
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ax25_decoder_bm_impl::decode (const uint8_t* in, size_t nitems)
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{
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size_t i;
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uint8_t dec_bit;
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for (i = 0; i < nitems; i++) {
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2017-07-29 22:51:06 +02:00
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/* Perform NRZI decoding */
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dec_bit = (~(((in[i] & 0x1) - d_prev_bit_nrzi) % 2)) & 0x1;
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d_prev_bit_nrzi = in[i] & 0x1;
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2016-07-01 23:18:44 +02:00
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2017-07-29 22:51:06 +02:00
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/* In AX.25 the LS bit is sent first */
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d_shift_reg = (d_shift_reg >> 1) | (dec_bit << 7);
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d_dec_b = (d_dec_b >> 1) | (dec_bit << 7);
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2016-07-07 16:57:06 +02:00
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2017-07-29 22:51:06 +02:00
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switch (d_state)
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{
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case NO_SYNC:
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if (d_shift_reg == AX25_SYNC_FLAG) {
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enter_sync_state ();
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}
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break;
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case IN_SYNC:
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d_decoded_bits++;
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if (d_decoded_bits == 8) {
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d_received_bytes++;
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d_decoded_bits = 0;
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if (d_shift_reg == AX25_SYNC_FLAG) {
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d_sync_received++;
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if (d_sync_received > d_sync_flags_thr) {
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enter_decoding_state ();
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}
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}
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if (d_received_bytes > 3) {
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reset_state ();
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}
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}
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break;
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case DECODING:
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/*
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* If the received byte was an AX.25 sync flag, there are two
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* possibilities. Either it was the end of frame or just a repeat of the
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* preamble.
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*
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* Also in case in error at the preamble, the G3RUH polynomial should
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* re-sync after 3 repetitions of the SYNC flag. For this reason we demand
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* that the distance between the last SYNC flag is greater than 3 bytes
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*/
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if (d_shift_reg == AX25_SYNC_FLAG) {
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if (d_received_bytes < 3) {
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enter_sync_state ();
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}
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else {
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/* Frame end */
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enter_frame_end ();
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}
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}
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else if ((d_shift_reg & 0xfc) == 0x7c) {
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/*This was a stuffed bit */
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d_dec_b <<= 1;
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}
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else if ((d_shift_reg & 0xfe) == 0xfe) {
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/*This can never happen... Error! */
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if (d_received_bytes > AX25_MIN_ADDR_LEN) {
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message_port_pub (
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pmt::mp ("failed_pdu"),
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pmt::make_blob (d_frame_buffer, d_received_bytes));
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}
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reset_state ();
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}
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else {
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d_decoded_bits++;
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if (d_decoded_bits == 8) {
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d_frame_buffer[d_received_bytes++] = d_dec_b;
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d_decoded_bits = 0;
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2016-07-01 23:18:44 +02:00
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2017-07-29 22:51:06 +02:00
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/*Check if the frame limit was reached */
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if (d_received_bytes >= d_max_frame_len) {
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LOG_WARN("Wrong size");
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message_port_pub (
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pmt::mp ("failed_pdu"),
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pmt::make_blob (d_frame_buffer, d_max_frame_len));
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reset_state ();
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}
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}
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}
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break;
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case FRAME_END:
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if (d_shift_reg == AX25_SYNC_FLAG) {
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d_dec_b = 0x0;
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d_shift_reg = 0x0;
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d_decoded_bits = 0;
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d_received_bytes = 0;
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d_state = FRAME_END;
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}
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else {
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d_decoded_bits++;
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if (d_decoded_bits / 8 > 3) {
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reset_state ();
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}
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}
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break;
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default:
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LOG_ERROR("Invalid decoding state");
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}
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2016-07-01 23:18:44 +02:00
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}
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}
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/*
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* Our virtual destructor.
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*/
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ax25_decoder_bm_impl::~ax25_decoder_bm_impl ()
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{
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delete [] d_frame_buffer;
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}
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void
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ax25_decoder_bm_impl::reset_state ()
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{
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d_state = NO_SYNC;
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2016-07-07 16:57:06 +02:00
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d_dec_b = 0x0;
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d_shift_reg = 0x0;
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2016-07-01 23:18:44 +02:00
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d_decoded_bits = 0;
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d_received_bytes = 0;
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d_prev_bit_nrzi = 0;
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2016-08-07 01:11:59 +02:00
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d_sync_received = 0;
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2016-07-01 23:18:44 +02:00
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}
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void
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ax25_decoder_bm_impl::enter_sync_state ()
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{
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d_state = IN_SYNC;
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2016-07-07 16:57:06 +02:00
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d_dec_b = 0x0;
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d_shift_reg = 0x0;
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2016-07-01 23:18:44 +02:00
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d_decoded_bits = 0;
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d_received_bytes = 0;
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2016-08-07 01:11:59 +02:00
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d_sync_received = 0;
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}
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void
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ax25_decoder_bm_impl::enter_decoding_state ()
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{
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d_state = DECODING;
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d_dec_b = 0x0;
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d_shift_reg = 0x0;
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d_decoded_bits = 0;
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d_received_bytes = 0;
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2016-07-01 23:18:44 +02:00
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}
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void
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ax25_decoder_bm_impl::enter_frame_end ()
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{
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uint16_t fcs;
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uint16_t recv_fcs = 0x0;
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/* First check if the size of the frame is valid */
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if (d_received_bytes < AX25_MIN_ADDR_LEN + sizeof(uint16_t)) {
|
2017-07-29 22:51:06 +02:00
|
|
|
message_port_pub (pmt::mp ("failed_pdu"),
|
|
|
|
pmt::make_blob (d_frame_buffer, d_received_bytes));
|
|
|
|
d_dec_b = 0x0;
|
|
|
|
d_shift_reg = 0x0;
|
|
|
|
d_decoded_bits = 0;
|
|
|
|
d_received_bytes = 0;
|
|
|
|
d_sync_received = 0;
|
|
|
|
d_state = FRAME_END;
|
|
|
|
return;
|
2016-07-01 23:18:44 +02:00
|
|
|
}
|
|
|
|
|
|
|
|
/* Check if the frame is correct using the FCS field */
|
|
|
|
fcs = ax25_fcs (d_frame_buffer, d_received_bytes - sizeof(uint16_t));
|
|
|
|
recv_fcs = (((uint16_t) d_frame_buffer[d_received_bytes - 1]) << 8)
|
2017-07-29 22:51:06 +02:00
|
|
|
| d_frame_buffer[d_received_bytes - 2];
|
2016-07-01 23:18:44 +02:00
|
|
|
|
|
|
|
if (fcs == recv_fcs) {
|
2017-07-29 22:51:06 +02:00
|
|
|
message_port_pub (
|
|
|
|
pmt::mp ("pdu"),
|
|
|
|
pmt::make_blob (d_frame_buffer,
|
|
|
|
d_received_bytes - sizeof(uint16_t)));
|
2016-07-01 23:18:44 +02:00
|
|
|
}
|
|
|
|
else {
|
2017-07-29 22:51:06 +02:00
|
|
|
message_port_pub (
|
|
|
|
pmt::mp ("failed_pdu"),
|
|
|
|
pmt::make_blob (d_frame_buffer,
|
|
|
|
d_received_bytes - sizeof(uint16_t)));
|
|
|
|
LOG_WARN("Wrong crc");
|
2016-07-01 23:18:44 +02:00
|
|
|
}
|
2016-07-07 16:57:06 +02:00
|
|
|
d_dec_b = 0x0;
|
|
|
|
d_shift_reg = 0x0;
|
2016-07-01 23:18:44 +02:00
|
|
|
d_decoded_bits = 0;
|
|
|
|
d_received_bytes = 0;
|
2016-08-07 01:11:59 +02:00
|
|
|
d_sync_received = 0;
|
2016-07-01 23:18:44 +02:00
|
|
|
d_state = FRAME_END;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
int
|
|
|
|
ax25_decoder_bm_impl::work (int noutput_items,
|
2017-07-29 22:51:06 +02:00
|
|
|
gr_vector_const_void_star &input_items,
|
|
|
|
gr_vector_void_star &output_items)
|
2016-07-01 23:18:44 +02:00
|
|
|
{
|
|
|
|
const uint8_t *in = (const uint8_t *) input_items[0];
|
|
|
|
|
2017-07-29 22:51:06 +02:00
|
|
|
if (d_descramble) {
|
|
|
|
descramble_and_decode (in, noutput_items);
|
2016-07-01 23:18:44 +02:00
|
|
|
}
|
2017-07-29 22:51:06 +02:00
|
|
|
else {
|
|
|
|
decode (in, noutput_items);
|
2016-07-01 23:18:44 +02:00
|
|
|
}
|
|
|
|
return noutput_items;
|
|
|
|
}
|
|
|
|
|
|
|
|
} /* namespace satnogs */
|
|
|
|
} /* namespace gr */
|
|
|
|
|