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#ifndef __DSSS_DEMOD_H__
#define __DSSS_DEMOD_H__
#include <stdint.h>
#include <unistd.h>
#define DSSS_GOLD_CODE_LENGTH ((1<<DSSS_GOLD_CODE_NBITS) - 1)
#define DSSS_GOLD_CODE_COUNT ((1<<DSSS_GOLD_CODE_NBITS) + 1)
#define DSSS_CORRELATION_LENGTH (DSSS_GOLD_CODE_LENGTH * DSSS_DECIMATION)
/* FIXME: move to makefile */
#define DSSS_MATCHER_CACHE_SIZE 8
/* FIXME: move to more appropriate header */
#define PAYLOAD_DATA_BYTE ((PAYLOAD_DATA_BIT+7)/8)
struct iir_biquad {
float a[2];
float b[3];
};
struct iir_biquad_state {
float reg[2];
};
struct cwt_iir_filter_state {
struct iir_biquad_state st[3];
};
struct group {
int len; /* length of group in samples */
float max; /* signed value of largest peak in group on any channel */
uint64_t max_ts; /* absolute position of above peak */
int max_ch; /* channel (gold sequence index) of above peak */
};
struct matcher_state {
int last_phase; /* 0 .. DSSS_CORRELATION_LENGTH */
int candidate_phase;
float last_score;
float candidate_score;
int last_skips;
int candidate_skips;
#if DSSS_GOLD_CODE_NBITS > 7
#error DSSS_GOLD_CODE_NBITS is too large for matcher_state.data data type (uint8_t)
#endif
uint8_t data[TRANSMISSION_SYMBOLS];
int data_pos;
uint8_t candidate_data;
};
struct dsss_demod_state {
float signal[DSSS_CORRELATION_LENGTH];
size_t signal_wpos;
float correlation[DSSS_GOLD_CODE_COUNT][DSSS_WAVELET_LUT_SIZE];
size_t correlation_wpos;
struct cwt_iir_filter_state cwt_filter;
struct group group;
struct matcher_state matcher_cache[DSSS_MATCHER_CACHE_SIZE];
};
extern void handle_dsss_received(uint8_t data[static TRANSMISSION_SYMBOLS]);
void dsss_demod_init(struct dsss_demod_state *st);
void dsss_demod_step(struct dsss_demod_state *st, float new_value, uint64_t ts);
#endif /* __DSSS_DEMOD_H__ */
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