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Code Issues Releases Wiki Activity

Improving GPS L1 CA telemetry decoder

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This commit is contained in:
Javier Arribas
2019-04-23 12:27:18 +02:00
parent 8ab202b666
commit 547559c0b8
1 changed files with 18 additions and 13 deletions
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31
src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l1_ca_telemetry_decoder_gs.cc
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@@ -218,8 +218,6 @@ bool gps_l1_ca_telemetry_decoder_gs::decode_subframe()
uint32_t GPS_frame_4bytes = 0;
float symbol_accumulator = 0;
bool subframe_synchro_confirmation = false;
bool CRC_ok = true;
for (float subframe_symbol : d_symbol_history)
{
// ******* SYMBOL TO BIT *******
@@ -269,11 +267,6 @@ bool gps_l1_ca_telemetry_decoder_gs::decode_subframe()
{
subframe_synchro_confirmation = true;
}
else
{
// std::cout << "word invalid sat " << this->d_satellite << std::endl;
CRC_ok = false;
}
// add word to subframe
// insert the word in the correct position of the subframe
std::memcpy(&subframe[word_index * GPS_WORD_LENGTH], &GPS_frame_4bytes, sizeof(uint32_t));
@@ -290,7 +283,7 @@ bool gps_l1_ca_telemetry_decoder_gs::decode_subframe()
// decode subframe
// NEW GPS SUBFRAME HAS ARRIVED!
if (CRC_ok)
if (subframe_synchro_confirmation)
{
int32_t subframe_ID = d_nav.subframe_decoder(subframe); //decode the subframe
if (subframe_ID > 0 and subframe_ID < 6)
@@ -329,21 +322,24 @@ bool gps_l1_ca_telemetry_decoder_gs::decode_subframe()
default:
break;
}
return true;
}
else
{
return false;
}
}
return subframe_synchro_confirmation;
}
void gps_l1_ca_telemetry_decoder_gs::reset()
{
gr::thread::scoped_lock lock(d_setlock); // require mutex with work function called by the scheduler
d_last_valid_preamble = d_sample_counter;
d_sent_tlm_failed_msg = false;
flag_TOW_set = false;
d_symbol_history.clear();
d_stat = 0;
DLOG(INFO) << "Telemetry decoder reset for satellite " << d_satellite;
}
@@ -400,6 +396,7 @@ int gps_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribute__
DLOG(INFO) << "Preamble detection for GPS L1 satellite " << this->d_satellite;
d_stat = 1; // enter into frame pre-detection status
}
flag_TOW_set = false;
break;
}
case 1: // possible preamble lock
@@ -438,6 +435,7 @@ int gps_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribute__
if (preamble_diff > d_preamble_period_symbols)
{
d_stat = 0; // start again
flag_TOW_set = false;
}
}
}
@@ -486,9 +484,16 @@ int gps_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribute__
// 2. Add the telemetry decoder information
if (d_flag_preamble == true)
{
d_TOW_at_current_symbol_ms = static_cast<uint32_t>(d_nav.d_TOW * 1000.0);
d_TOW_at_Preamble_ms = static_cast<uint32_t>(d_nav.d_TOW * 1000.0);
flag_TOW_set = true;
if (!d_nav.d_TOW == 0)
{
d_TOW_at_current_symbol_ms = static_cast<uint32_t>(d_nav.d_TOW * 1000.0);
d_TOW_at_Preamble_ms = static_cast<uint32_t>(d_nav.d_TOW * 1000.0);
flag_TOW_set = true;
}
else
{
DLOG(INFO) << "Received GPS L1 TOW equal to zero at sat " << d_nav.i_satellite_PRN;
}
}
else
{