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EPIRB TX SGB support (#3263)

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* Update BEACONS.TXT
Added test beacon with 3 bch1 errors and 2 bch2 errors to test multiple bit error correction.
* Fist step to SGB format
* Added SGB to manual mode.
* SGB support
- Added SGB frame to beacons file
- Fixed hex display for SGB
- Fixed frame type option display
- Fixed self-test mode activation logic
- Fixed PRN for self-test mode
This commit is contained in:
Frederic BORRY
2026-07-09 10:36:26 +02:00
committed by GitHub
parent 7513cd46fc
commit d11669f711
7 changed files with 523 additions and 127 deletions
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firmware/baseband/proc_epirb_tx.hpp
+49 -5
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@@ -26,6 +26,7 @@
#include "baseband_thread.hpp"
#include "portapack_shared_memory.hpp"
#include "tonesets.hpp"
#include <algorithm>
#include <cmath>
/**
@@ -42,8 +43,12 @@ class EPIRBTXProcessor : public BasebandProcessor {
private:
// True when the processor has received a configuration message from the app
bool configured{false};
// True when in BPSK transmission mode, false for AM transmission mode
bool mode_bpsk{false};
// True when in 406 MHz transmission mode, false for AM transmission mode
bool mode_406{false};
// True when current 406 frame is a 2nd generation DSSS-OQPSK frame
bool mode_sgb{false};
// True when in self-test mode (detected from bit 5 of message.data)
bool mode_sgb_selftest{true};
// True when the transmission has to be stopped (e.g. at the end of a frame)
bool end_of_transmission{};
@@ -55,10 +60,15 @@ class EPIRBTXProcessor : public BasebandProcessor {
// Configured post-count value: used to continue the carrier for config_post_count samples after the end of a frame
uint32_t config_post_count = 0;
// Data of the frame to send in BPSK mode
uint8_t frame_data[18]{0};
// Size of the frame to send in BPSK mode
// Data of the frame to send in 406 mode (FGB BPSK or SGB DSSS-OQPSK)
static constexpr uint8_t frame_data_max_len = 32;
static constexpr uint8_t frame_data_fgb_max_len = 18;
static constexpr uint8_t frame_data_sgb_len = 32; // ceil(250 / 8)
uint8_t frame_data[frame_data_max_len]{0};
// Size of the frame to send in bytes
uint8_t frame_data_len = 0;
// Size of the frame payload in bits
uint16_t frame_sgb_bits_len = 0;
// BPSK parameters: Target phase +/-1.1 RAD as per COSPAS/SARSAT specifications
static constexpr float phase_rad = 1.1f;
@@ -89,6 +99,40 @@ class EPIRBTXProcessor : public BasebandProcessor {
// Position in the current manchester bit
bool manchester_half = false; // false = first half
// 2G SGB DSSS-OQPSK parameters
static constexpr uint16_t sgb_message_bits = 256; // 250 bits of data + 6 bits padding
static constexpr uint32_t sgb_chip_rate = 38400;
static constexpr uint32_t sgb_chips_per_bit = 256;
static constexpr uint32_t sgb_preamble_bits_per_channel = 25;
static constexpr uint32_t sgb_bits_per_channel = 150;
static constexpr uint32_t sgb_segment_chips = 38400;
static constexpr uint32_t sgb_samples_per_chip = TONES_SAMPLERATE / sgb_chip_rate;
static constexpr uint32_t sgb_half_chip_samples = sgb_samples_per_chip / 2;
// SGB burst duration is exactly 1 second.
static constexpr uint32_t sgb_total_samples = sgb_segment_chips * sgb_samples_per_chip;
static constexpr int8_t sgb_chip_amplitude = 90;
static constexpr uint32_t sgb_init_normal_i = 0x1;
static constexpr uint32_t sgb_init_normal_q = 0x1AC1FC;
static constexpr uint32_t sgb_init_selftest_i = 0x52C9F0;
static constexpr uint32_t sgb_init_selftest_q = 0x3CE928;
struct SGBChannelState {
uint32_t prn_state = 1;
uint32_t chip_index = 0;
uint32_t sample_in_chip = 0;
int8_t chip_level = 0;
};
SGBChannelState sgb_i{};
SGBChannelState sgb_q{};
uint32_t sgb_sample_counter = 0;
uint8_t get_frame_bit(uint16_t bit_pos) const;
int8_t compute_sgb_chip_level(SGBChannelState& channel, bool q_channel);
int8_t sample_sgb_channel(SGBChannelState& channel, bool q_channel);
void init_sgb_channel(SGBChannelState& channel, uint32_t initial_state);
// 127.5 AM signal parameters
static const uint32_t sweep_rate = 3; // 3 Hz
static const uint32_t f_min = 300; // Sweep min frequency (Hz)