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gr-satnogs/lib/ax100_decoder.cc

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/* -*- c++ -*- */
/*
* gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
*
* Copyright (C) 2019, Libre Space Foundation <http://libre.space>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <gnuradio/io_signature.h>
#include <satnogs/ax100_decoder.h>
#include <satnogs/golay24.h>
#include <satnogs/metadata.h>
#include <satnogs/utils.h>
#include <satnogs/log.h>
extern "C" {
#include <fec.h>
}
namespace gr {
namespace satnogs {
decoder::decoder_sptr
ax100_decoder::make(const std::vector<uint8_t> &preamble,
size_t preamble_threshold,
const std::vector<uint8_t> &sync, size_t sync_threshold,
crc::crc_t crc, whitening::whitening_sptr descrambler,
bool enable_rs)
{
return decoder::decoder_sptr(
new ax100_decoder(preamble, preamble_threshold, sync, sync_threshold,
crc, descrambler, enable_rs));
}
ax100_decoder::ax100_decoder(const std::vector<uint8_t> &preamble,
size_t preamble_threshold,
const std::vector<uint8_t> &sync,
size_t sync_threshold,
crc::crc_t crc,
whitening::whitening_sptr descrambler,
bool enable_rs) :
decoder(sizeof(uint8_t), enable_rs ? 255 : 1024),
d_preamble(preamble.size() * 8),
d_preamble_shift_reg(preamble.size() * 8),
d_preamble_len(preamble.size() * 8),
d_preamble_thrsh(preamble_threshold),
d_sync(sync.size() * 8),
d_sync_shift_reg(sync.size() * 8),
d_sync_len(sync.size() * 8),
d_sync_thrsh(sync_threshold),
d_crc(crc),
d_descrambler(descrambler),
d_rs(enable_rs),
d_state(SEARCHING),
d_cnt(0),
d_len(0),
/* Coded Golay 24 bits */
d_length_field_len(3),
d_pdu(new uint8_t[1024])
{
for (uint8_t b : preamble) {
d_preamble <<= (b >> 7);
d_preamble <<= ((b >> 6) & 0x1);
d_preamble <<= ((b >> 5) & 0x1);
d_preamble <<= ((b >> 4) & 0x1);
d_preamble <<= ((b >> 3) & 0x1);
d_preamble <<= ((b >> 2) & 0x1);
d_preamble <<= ((b >> 1) & 0x1);
d_preamble <<= (b & 0x1);
}
for (uint8_t b : sync) {
d_sync <<= (b >> 7);
d_sync <<= ((b >> 6) & 0x1);
d_sync <<= ((b >> 5) & 0x1);
d_sync <<= ((b >> 4) & 0x1);
d_sync <<= ((b >> 3) & 0x1);
d_sync <<= ((b >> 2) & 0x1);
d_sync <<= ((b >> 1) & 0x1);
d_sync <<= (b & 0x1);
}
if (d_sync_len < 8) {
throw std::invalid_argument("SYNC word should be at least 8 bits");
}
if (d_preamble_len < 2 * d_preamble_thrsh) {
throw std::invalid_argument(
"Too many error bits are allowed for the preamble."
"Consider lowering the threshold");
}
if (d_sync_len < 2 * d_sync_thrsh) {
throw std::invalid_argument(
"Too many error bits are allowed for the sync word. "
"Consider lowering the threshold");
}
}
ax100_decoder::~ax100_decoder()
{
delete[] d_pdu;
}
decoder_status_t
ax100_decoder::decode(const void *in, int len)
{
decoder_status_t status;
switch (d_state) {
case SEARCHING:
status.consumed = search_preamble((const uint8_t *) in, len);
break;
case SEARCHING_SYNC:
status.consumed = search_sync((const uint8_t *) in, len);
break;
case DECODING_FRAME_LEN:
status.consumed = decode_frame_len((const uint8_t *) in, len);
break;
case DECODING_PAYLOAD:
decode_payload(status, (const uint8_t *) in, len);
break;
default:
throw std::runtime_error("ax100_decoder: Invalid decoding state");
}
return status;
}
void
ax100_decoder::reset()
{
if (d_descrambler) {
d_descrambler->reset();
}
d_cnt = 0;
d_state = SEARCHING;
d_preamble_shift_reg.reset();
d_sync_shift_reg.reset();
}
size_t
ax100_decoder::input_multiple() const
{
return 8;
}
int
ax100_decoder::search_preamble(const uint8_t *in, int len)
{
/* We support also cases, where a repeated preamble is not used (pure CCSDS )*/
if (d_preamble_len == 0) {
d_state = SEARCHING_SYNC;
return search_sync(in, len);
}
for (int i = 0; i < len; i++) {
d_preamble_shift_reg <<= in[i];
shift_reg tmp = d_preamble_shift_reg ^ d_preamble;
if (tmp.count() <= d_preamble_thrsh) {
d_state = SEARCHING_SYNC;
d_cnt = 0;
return i + 1;
}
}
return len;
}
int
ax100_decoder::search_sync(const uint8_t *in, int len)
{
for (int i = 0; i < len; i++) {
d_sync_shift_reg <<= in[i];
shift_reg tmp = d_sync_shift_reg ^ d_sync;
d_cnt++;
if (tmp.count() <= d_sync_thrsh) {
LOG_WARN("Decoding");
d_state = DECODING_FRAME_LEN;
d_cnt = 0;
return i + 1;
}
/* The sync word should be available by now */
if (d_cnt > d_preamble_len * 2 + d_sync_len) {
reset();
return i + 1;
}
}
return len;
}
int
ax100_decoder::decode_frame_len(const uint8_t *in, int len)
{
const int s = len / 8;
for (int i = 0; i < s; i++) {
uint8_t b = 0x0;
b = in[i * 8] << 7;
b |= in[i * 8 + 1] << 6;
b |= in[i * 8 + 2] << 5;
b |= in[i * 8 + 3] << 4;
b |= in[i * 8 + 4] << 3;
b |= in[i * 8 + 5] << 2;
b |= in[i * 8 + 6] << 1;
b |= in[i * 8 + 7];
d_pdu[d_cnt++] = b;
if (d_cnt == d_length_field_len) {
uint32_t coded_len = (d_pdu[0] << 16) | (d_pdu[1] << 8) | d_pdu[2];
print_pdu((const uint8_t *)&coded_len, 4);
uint32_t len;
golay24 g = golay24();
if (g.decode24(&len, coded_len)) {
d_len = len & 0xFF;
//d_len += crc::crc_size(d_crc);
LOG_WARN("Len: %u", d_len);
if (d_len > max_frame_len()) {
reset();
return (i + 1) * 8;
}
/* All good! Proceed with decoding */
d_cnt = 0;
d_state = DECODING_PAYLOAD;
memset(d_pdu, 0, max_frame_len());
return (i + 1) * 8;
}
else {
reset();
return (i + 1) * 8;
}
}
}
return s * 8;
}
void
ax100_decoder::decode_payload(decoder_status_t &status,
const uint8_t *in, int len)
{
const int s = len / 8;
for (int i = 0; i < s; i++) {
uint8_t b = 0x0;
b = in[i * 8] << 7;
b |= in[i * 8 + 1] << 6;
b |= in[i * 8 + 2] << 5;
b |= in[i * 8 + 3] << 4;
b |= in[i * 8 + 4] << 3;
b |= in[i * 8 + 5] << 2;
b |= in[i * 8 + 6] << 1;
b |= in[i * 8 + 7];
d_pdu[d_cnt++] = b;
if (d_cnt == d_len) {
if (d_descrambler) {
d_descrambler->descramble(d_pdu, d_pdu, d_len, false);
}
metadata::add_time_iso8601(status.data);
/* If RS is used tru to decode the received frame */
if (d_rs) {
int ret = decode_rs_8(d_pdu, NULL, 0, 255 - d_len);
/* Drop the parity */
d_len -= 32;
if (ret > - 1) {
metadata::add_corrected_bits(status.data, ret);
}
else {
reset();
status.consumed = (i + 1) * 8;
return;
}
}
metadata::add_time_iso8601(status.data);
metadata::add_pdu(status.data, d_pdu, d_len - crc::crc_size(d_crc));
metadata::add_crc_valid(status.data, check_crc());
reset();
status.decode_success = true;
status.consumed = (i + 1) * 8;
return;
}
}
status.consumed = s * 8;
}
bool
ax100_decoder::check_crc()
{
uint16_t crc16_c;
uint16_t crc16_received;
uint32_t crc32_c;
uint32_t crc32_received;
switch (d_crc) {
case crc::CRC_NONE:
return true;
case crc::CRC32_C:
crc32_c = crc::crc32_c(d_pdu, d_len - 4);
memcpy(&crc32_received, d_pdu + d_len - 4, 4);
crc32_received = ntohl(crc32_received);
LOG_WARN("Received: 0x%02x Computed: 0x%02x", crc32_received, crc32_c);
//print_pdu(d_pdu, d_len);
if (crc32_c == crc32_received) {
return true;
}
return false;
default:
throw std::runtime_error("ax100_decoder: Invalid CRC");
}
}
} /* namespace satnogs */
} /* namespace gr */
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