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Fix GPS L1 CA telemetry decoder for 180 deg. PLL lock

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This commit is contained in:
Javier Arribas 2021-09-27 13:53:14 +02:00
parent 715987e749
commit 003ae61316
2 changed files with 19 additions and 7 deletions
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24
src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l1_ca_telemetry_decoder_gs.cc
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@ -251,7 +251,7 @@ void gps_l1_ca_telemetry_decoder_gs::set_channel(int32_t channel)
} }
bool gps_l1_ca_telemetry_decoder_gs::decode_subframe() bool gps_l1_ca_telemetry_decoder_gs::decode_subframe(bool flag_invert)
{ {
std::array<char, GPS_SUBFRAME_LENGTH> subframe{}; std::array<char, GPS_SUBFRAME_LENGTH> subframe{};
int32_t frame_bit_index = 0; int32_t frame_bit_index = 0;
@ -262,11 +262,20 @@ bool gps_l1_ca_telemetry_decoder_gs::decode_subframe()
{ {
// ******* SYMBOL TO BIT ******* // ******* SYMBOL TO BIT *******
// symbol to bit // symbol to bit
if (subframe_symbol > 0) if (flag_invert == false)
{ {
GPS_frame_4bytes += 1; // insert the telemetry bit in LSB if (subframe_symbol > 0)
{
GPS_frame_4bytes += 1; // insert the telemetry bit in LSB
}
}
else
{
if (subframe_symbol < 0)
{
GPS_frame_4bytes += 1; // insert the inverted telemetry bit in LSB
}
} }
// ******* bits to words ****** // ******* bits to words ******
frame_bit_index++; frame_bit_index++;
if (frame_bit_index == 30) if (frame_bit_index == 30)
@ -467,7 +476,10 @@ int gps_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribute__
d_flag_PLL_180_deg_phase_locked = false; d_flag_PLL_180_deg_phase_locked = false;
} }
DLOG(INFO) << "Preamble detection for GPS L1 satellite " << this->d_satellite; DLOG(INFO) << "Preamble detection for GPS L1 satellite " << this->d_satellite;
if (decode_subframe()) d_prev_GPS_frame_4bytes = 0;
std::cout << "Preamble detection " << corr_value << " for GPS L1 satellite " << this->d_satellite << "\n";
if (decode_subframe(d_flag_PLL_180_deg_phase_locked))
{ {
d_CRC_error_counter = 0; d_CRC_error_counter = 0;
d_flag_preamble = true; // valid preamble indicator (initialized to false every work()) d_flag_preamble = true; // valid preamble indicator (initialized to false every work())
@ -493,7 +505,7 @@ int gps_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribute__
// 0. fetch the symbols into an array // 0. fetch the symbols into an array
d_preamble_index = d_sample_counter; // record the preamble sample stamp (t_P) d_preamble_index = d_sample_counter; // record the preamble sample stamp (t_P)
if (decode_subframe()) if (decode_subframe(d_flag_PLL_180_deg_phase_locked))
{ {
d_CRC_error_counter = 0; d_CRC_error_counter = 0;
d_flag_preamble = true; // valid preamble indicator (initialized to false every work()) d_flag_preamble = true; // valid preamble indicator (initialized to false every work())

2
src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l1_ca_telemetry_decoder_gs.h
View File

@ -74,7 +74,7 @@ private:
gps_l1_ca_telemetry_decoder_gs(const Gnss_Satellite &satellite, const Tlm_Conf &conf); gps_l1_ca_telemetry_decoder_gs(const Gnss_Satellite &satellite, const Tlm_Conf &conf);
bool gps_word_parityCheck(uint32_t gpsword); bool gps_word_parityCheck(uint32_t gpsword);
bool decode_subframe(); bool decode_subframe(bool flag_invert);
Gps_Navigation_Message d_nav; Gps_Navigation_Message d_nav;
Gnss_Satellite d_satellite; Gnss_Satellite d_satellite;