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Minor changes

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This commit is contained in:
Antonio Ramos 2018-04-12 17:01:07 +02:00
parent f92dd4dc83
commit ad220dd279
1 changed files with 19 additions and 12 deletions
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31
src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l1_ca_telemetry_decoder_cc.cc
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@ -172,7 +172,7 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
unsigned int required_symbols = GPS_CA_PREAMBLE_LENGTH_SYMBOLS;
d_flag_preamble = false;
if (d_symbol_history.size() > required_symbols and d_make_correlation)
if ((d_symbol_history.size() > required_symbols) and (d_make_correlation or !d_flag_frame_sync))
{
//******* preamble correlation ********
for (unsigned int i = 0; i < GPS_CA_PREAMBLE_LENGTH_SYMBOLS; i++)
@ -181,24 +181,22 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
{
if (d_symbol_history.at(i).Prompt_I < 0) // symbols clipping
{
corr_value -= d_preambles_symbols[i] * d_symbol_history.at(i).correlation_length_ms;
corr_value -= d_preambles_symbols[i];
}
else
{
corr_value += d_preambles_symbols[i] * d_symbol_history.at(i).correlation_length_ms;
corr_value += d_preambles_symbols[i];
}
}
if (corr_value >= GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
{
d_symbol_counter_corr = 0;
d_make_correlation = false;
break;
}
}
if (std::abs(corr_value) >= GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
{
d_symbol_counter_corr++;
}
}
//******* frame sync ******************
if (abs(corr_value) == GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
if (std::abs(corr_value) == GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
{
//TODO: Rewrite with state machine
if (d_stat == 0)
@ -215,12 +213,14 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
}
else if (d_stat == 1) //check 6 seconds of preamble separation
{
preamble_diff_ms = round(((static_cast<double>(d_symbol_history.at(0).Tracking_sample_counter) - d_preamble_time_samples) / static_cast<double>(d_symbol_history.at(0).fs)) * 1000.0);
if (abs(preamble_diff_ms - GPS_SUBFRAME_MS) < 1)
preamble_diff_ms = std::round(((static_cast<double>(d_symbol_history.at(0).Tracking_sample_counter) - d_preamble_time_samples) / static_cast<double>(d_symbol_history.at(0).fs)) * 1000.0);
if (std::abs(preamble_diff_ms - GPS_SUBFRAME_MS) < 1)
{
DLOG(INFO) << "Preamble confirmation for SAT " << this->d_satellite;
d_GPS_FSM.Event_gps_word_preamble();
d_flag_preamble = true;
d_make_correlation = false;
d_symbol_counter_corr = 0;
d_preamble_time_samples = d_symbol_history.at(0).Tracking_sample_counter; // record the PRN start sample index associated to the preamble
if (!d_flag_frame_sync)
{
@ -245,6 +245,11 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
}
else
{
d_symbol_counter_corr++;
if (d_symbol_counter_corr > (GPS_SUBFRAME_MS - GPS_CA_TELEMETRY_SYMBOLS_PER_BIT))
{
d_make_correlation = true;
}
if (d_stat == 1)
{
preamble_diff_ms = round(((static_cast<double>(d_symbol_history.at(0).Tracking_sample_counter) - static_cast<double>(d_preamble_time_samples)) / static_cast<double>(d_symbol_history.at(0).fs)) * 1000.0);
@ -254,6 +259,8 @@ int gps_l1_ca_telemetry_decoder_cc::general_work(int noutput_items __attribute__
d_stat = 0; //lost of frame sync
d_flag_frame_sync = false;
flag_TOW_set = false;
d_make_correlation = true;
d_symbol_counter_corr = 0;
}
}
}