ua1zbe
a1206d6fd4
Features: - VFO mode with direct frequency input - POCSAG decoder (512/1200 baud) with BCH(31,21) correction - Full-screen Spectrum analyzer - FM Radio receiver - RSSI signal indicator overlay - Custom boot splash (UA1ZBE / POCSAG pager / build date) Architecture: - app/mode.c — mode dispatcher (VFO/POCSAG/Spectrum/FM) - app/boot_splash.c — 2-second boot splash - app/pocsag/ — POCSAG decoder + BCH correction - app/display_rssi.c — RSSI indicator - main.c — entry point with custom init - syscalls.c — bare-metal _sbrk stub Build: arm-none-eabi-gcc -Os -flto -Wall -Werror -Wextra Size: 57.9KB Flash / 3.6KB RAM Controls: - 0-9: Direct frequency input (VFO) - SK2: POCSAG mode - SK1: Spectrum analyzer - 0: FM Radio - EXIT: Return to VFO - F/*: Toggle 512/1200 baud (in POCSAG)
151 lines
4.4 KiB
C
151 lines
4.4 KiB
C
/* UA1ZBE Custom Firmware - POCSAG Decoder
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*
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* Decodes POCSAG paging signals from FM discriminator output.
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* Supports 512 and 1200 baud rates with dynamic switching.
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*
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* POCSAG Protocol:
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* - Preamble: 0xAAAAAAAB (at least 576 bits of alternating 1010... ending with 1)
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* - Sync word: 0x7CD21538
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* - Data words: 32-bit (21 data + 10 BCH + 1 parity)
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* - BCH(31,21) code, corrects up to 2 errors per word
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*
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* Architecture:
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* - Samples audio from BK4819 discriminator (REG_69 AF output or FSK FIFO)
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* - Zero-crossing detection for bit slicing
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* - State machine: IDLE -> PREAMBLE -> SYNC -> DATA
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* - Ring buffer for decoded messages
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* - Zero malloc — all static allocation
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*/
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#ifndef APP_POCSAG_POCSAG_H
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#define APP_POCSAG_POCSAG_H
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#include <stdbool.h>
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#include <stdint.h>
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/* POCSAG baud rates */
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#define POCSAG_BAUD_512 512
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#define POCSAG_BAUD_1200 1200
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/* Maximum message length in bytes (arbitrary, fits in static buffer) */
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#define POCSAG_MSG_MAX_LEN 64
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/* Maximum messages in ring buffer */
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#define POCSAG_MSG_POOL_SIZE 8
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/* Decoded message structure */
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typedef struct {
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uint32_t address; /* Address (21-bit frame address) */
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uint8_t func; /* Function code (2 bits) */
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char text[POCSAG_MSG_MAX_LEN]; /* Decoded text (alpha pager) */
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uint8_t text_len; /* Length of decoded text */
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bool is_alpha; /* true = alpha pager, false = numeric */
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uint32_t timestamp; /* System tick when received */
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} pocsag_msg_t;
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/* Decoder state machine states */
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typedef enum {
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POCSAG_STATE_IDLE = 0,
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POCSAG_STATE_PREAMBLE,
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POCSAG_STATE_SYNC,
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POCSAG_STATE_DATA
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} pocsag_state_t;
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/* Decoder context — all static, no malloc */
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typedef struct {
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/* Configuration */
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uint32_t baud_rate; /* Current baud rate: 512 or 1200 */
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/* State machine */
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pocsag_state_t state;
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/* Bit accumulation */
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uint32_t shift_reg; /* Shift register for incoming bits */
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uint8_t bit_count; /* Number of bits collected in shift_reg */
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uint8_t preamble_count; /* Consecutive alternating bits in preamble */
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/* Sync detection */
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uint8_t sync_word_count; /* Number of sync words found in a row */
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/* Word collection */
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uint8_t batch_count; /* Words in current batch (0-16) */
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uint8_t word_in_batch; /* Current word position in batch */
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/* Message assembly */
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uint32_t current_address;
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uint8_t current_func;
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uint8_t msg_data[POCSAG_MSG_MAX_LEN];
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uint8_t msg_len;
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bool msg_is_alpha;
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/* Ring buffer of decoded messages */
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pocsag_msg_t messages[POCSAG_MSG_POOL_SIZE];
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volatile uint8_t msg_read_idx;
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volatile uint8_t msg_write_idx;
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volatile uint8_t msg_count;
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/* Statistics */
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uint32_t total_bits;
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uint32_t total_words;
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uint32_t corrected_errors;
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uint32_t uncorrectable_errors;
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/* Flag for new message available */
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volatile bool msg_available;
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/* Signal active flag */
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bool signal_detected;
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} pocsag_decoder_t;
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/* Global decoder instance */
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extern pocsag_decoder_t gPocsag;
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/* === API === */
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/* Initialize decoder, set baud rate */
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void POCSAG_Init(uint32_t baud_rate);
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/* Switch baud rate dynamically (512 <-> 1200) */
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void POCSAG_SwitchBaud(uint32_t baud_rate);
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/* Get current baud rate */
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uint32_t POCSAG_GetBaud(void);
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/* Feed audio sample (12-bit ADC value from discriminator)
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* Call this from the 10ms timeslice or a dedicated sampling timer.
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* Returns true if a bit was detected. */
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bool POCSAG_FeedSample(uint16_t audio_sample);
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/* Feed a single bit (after external bit-slicing) */
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void POCSAG_FeedBit(bool bit);
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/* Check if a decoded message is available (non-blocking) */
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bool POCSAG_MessageAvailable(void);
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/* Pop the next decoded message from the ring buffer */
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bool POCSAG_GetMessage(pocsag_msg_t *msg);
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/* Get decoder state (for display) */
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pocsag_state_t POCSAG_GetState(void);
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/* Get signal detection status */
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bool POCSAG_SignalDetected(void);
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/* Reset decoder to idle state */
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void POCSAG_Reset(void);
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/* Process decoder state machine (call from main loop) */
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void POCSAG_Process(void);
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/* Configure BK4819 for POCSAG reception on given frequency */
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void POCSAG_ConfigureRadio(uint32_t frequency_hz);
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/* Stop POCSAG reception, restore normal RX */
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void POCSAG_Stop(void);
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/* Get state description string */
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const char *POCSAG_StateString(pocsag_state_t state);
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#endif /* APP_POCSAG_POCSAG_H */
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