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Code Issues Releases Wiki Activity

Adding TOW update consistency check in GPS L5 telemetry decoder

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This commit is contained in:
Javier Arribas
2019-06-21 18:06:48 +02:00
parent 12e26fe318
commit bfae31390f
1 changed files with 28 additions and 7 deletions
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29
src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l5_telemetry_decoder_gs.cc
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@@ -64,7 +64,7 @@ gps_l5_telemetry_decoder_gs::gps_l5_telemetry_decoder_gs(
this->message_port_register_out(pmt::mp("telemetry_to_trk")); this->message_port_register_out(pmt::mp("telemetry_to_trk"));
d_last_valid_preamble = 0; d_last_valid_preamble = 0;
d_sent_tlm_failed_msg = false; d_sent_tlm_failed_msg = false;
d_max_symbols_without_valid_frame = GPS_L5_CNAV_DATA_PAGE_BITS * GPS_L5_SAMPLES_PER_SYMBOL * GPS_L5_SYMBOLS_PER_BIT * 20; //rise alarm if 20 consecutive subframes have no valid CRC d_max_symbols_without_valid_frame = GPS_L5_CNAV_DATA_PAGE_BITS * GPS_L5_SAMPLES_PER_SYMBOL * GPS_L5_SYMBOLS_PER_BIT * 10; //rise alarm if 20 consecutive subframes have no valid CRC
// initialize internal vars // initialize internal vars
d_dump = dump; d_dump = dump;
@@ -152,7 +152,9 @@ void gps_l5_telemetry_decoder_gs::set_channel(int32_t channel)
void gps_l5_telemetry_decoder_gs::reset() void gps_l5_telemetry_decoder_gs::reset()
{ {
d_last_valid_preamble = d_sample_counter; d_last_valid_preamble = d_sample_counter;
d_TOW_at_current_symbol_ms = 0;
d_sent_tlm_failed_msg = false; d_sent_tlm_failed_msg = false;
d_flag_valid_word = false;
DLOG(INFO) << "Telemetry decoder reset for satellite " << d_satellite; DLOG(INFO) << "Telemetry decoder reset for satellite " << d_satellite;
} }
@@ -211,7 +213,7 @@ int gps_l5_telemetry_decoder_gs::general_work(int noutput_items __attribute__((u
symbol_value = -1; symbol_value = -1;
} }
new_sym = true; new_sym = true;
sym_hist.clear(); //sym_hist.clear();
} }
else else
{ {
@@ -268,15 +270,33 @@ int gps_l5_telemetry_decoder_gs::general_work(int noutput_items __attribute__((u
// update TOW at the preamble instant // update TOW at the preamble instant
d_TOW_at_Preamble_ms = msg.tow * 6000; d_TOW_at_Preamble_ms = msg.tow * 6000;
d_last_valid_preamble = d_sample_counter;
// The time of the last input symbol can be computed from the message ToW and // The time of the last input symbol can be computed from the message ToW and
// delay by the formulae: // delay by the formulae:
// \code // \code
// symbolTime_ms = msg->tow * 6000 + *pdelay * 10 + (12 * 10); 12 symbols of the encoder's transitory // symbolTime_ms = msg->tow * 6000 + *pdelay * 10 + (12 * 10); 12 symbols of the encoder's transitory
//check TOW update consistency
uint32_t last_d_TOW_at_current_symbol_ms = d_TOW_at_current_symbol_ms;
d_TOW_at_current_symbol_ms = msg.tow * 6000 + (delay + 12) * GPS_L5I_SYMBOL_PERIOD_MS; d_TOW_at_current_symbol_ms = msg.tow * 6000 + (delay + 12) * GPS_L5I_SYMBOL_PERIOD_MS;
d_flag_valid_word = true; if (last_d_TOW_at_current_symbol_ms != 0 and abs(static_cast<int64_t>(d_TOW_at_current_symbol_ms) - int64_t(last_d_TOW_at_current_symbol_ms)) > 1)
{
DLOG(INFO) << "Warning: GPS L5 TOW update in ch " << d_channel
<< " does not match the TLM TOW counter " << static_cast<int64_t>(d_TOW_at_current_symbol_ms) - int64_t(last_d_TOW_at_current_symbol_ms) << " ms "
<< " with delay: " << delay << " msg tow: " << msg.tow * 6000 << " ms \n";
d_TOW_at_current_symbol_ms = 0;
d_flag_valid_word = false;
} }
else else
{
d_last_valid_preamble = d_sample_counter;
d_flag_valid_word = true;
}
}
else
{
if (d_flag_valid_word)
{ {
d_TOW_at_current_symbol_ms += GPS_L5I_PERIOD_MS; d_TOW_at_current_symbol_ms += GPS_L5I_PERIOD_MS;
if (current_synchro_data.Flag_valid_symbol_output == false) if (current_synchro_data.Flag_valid_symbol_output == false)
@@ -284,6 +304,7 @@ int gps_l5_telemetry_decoder_gs::general_work(int noutput_items __attribute__((u
d_flag_valid_word = false; d_flag_valid_word = false;
} }
} }
}
if (d_flag_valid_word == true) if (d_flag_valid_word == true)
{ {