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decoding WIP

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This commit is contained in:
jaseg 2020-03-09 10:17:14 +01:00
parent 55ebbcbdbc
commit b4d5293d04
5 changed files with 120 additions and 25 deletions
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64
controller/fw/src/dsss_demod.c
View file

@ -46,17 +46,16 @@ void debug_print_vector(const char *name, size_t len, const float *data, size_t
#endif
#ifdef SIMULATION
void dsss_demod_step(struct dsss_demod_state *st, float new_value, size_t sim_pos, int record_channel) {
void dsss_demod_step(struct dsss_demod_state *st, float new_value, uint64_t ts, int record_channel) {
bool debug = (record_channel == -1)
&& (sim_pos > 1000)
&& (sim_pos % DSSS_CORRELATION_LENGTH == DSSS_CORRELATION_LENGTH-1);
&& (ts > 1000)
&& (ts % DSSS_CORRELATION_LENGTH == DSSS_CORRELATION_LENGTH-1);
if (debug) DEBUG_PRINT("Iteration %zd: signal=%f", sim_pos, new_value);
if (debug) DEBUG_PRINT("Iteration %zd: signal=%f", ts, new_value);
#else
void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
#endif
//const float peak_group_threshold = 0.05 * DSSS_CORRELATION_LENGTH;
//const float hole_patching_threshold = 0.01 * DSSS_CORRELATION_LENGTH;
st->signal[st->signal_wpos] = new_value;
@ -89,7 +88,7 @@ void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
float max_val = st->group.max;
int max_ch = st->group.max_ch;
int max_idx = st->group.max_idx + 1;
int max_ts = st->group.max_ts;
bool found = false;
for (size_t i=0; i<DSSS_GOLD_CODE_COUNT; i++) {
float val = cwt[i] / avg[i];
@ -100,7 +99,7 @@ void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
if (fabs(val) > fabs(max_val)) {
max_val = val;
max_ch = i;
max_idx = st->group.len;
max_ts = ts;
}
}
@ -109,7 +108,7 @@ void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
st->group.len++;
st->group.max = max_val;
st->group.max_ch = max_ch;
st->group.max_idx = max_idx;
st->group.max_ts = max_ts;
return;
}
@ -120,15 +119,60 @@ void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
/* A group ended. Process result. */
if (record_channel == -1)
DEBUG_PRINT("GROUP FOUND: %8d len=%3d max=%f ch=%d offx=%d",
sim_pos, st->group.len, st->group.max, st->group.max_ch, st->group.max_idx);
ts, st->group.len, st->group.max, st->group.max_ch, st->group.max_ts);
/* reset grouping state */
st->group.len = 0;
st->group.max_idx = 0;
st->group.max_ts = 0;
st->group.max_ch = 0;
st->group.max = 0.0f;
}
float score_group(const struct group *g, uint64_t ts) {
return fabs(g->max); /* Possibly at time penalty 1/(ts-max_ts) later */
}
ssize_t group_cache_insertion_index(const struct group *g, const struct group *cache, size_t cache_size, uint64_t ts) {
float min_score = INFINITY;
ssize_t min_idx = -1;
for (size_t i=0; i<cache_size; i++) {
/* If we find an empty or expired entry, use that */
if (cache[i].max_ts == 0 || ts - cache[i].max_ts > group_cache_expiration)
return i;
/* Otherwise check weakest entry */
float score = score_group(&cache[i]);
if (score < min_score) {
min_idx = i;
min_score = score;
}
}
/* Return weakest group if weaker than candidate */
if (min_score < score_group(g))
return min_idx;
return -1;
}
void group_received(struct dsss_demod_state *st, uint64_t ts) {
/* TODO make these constants configurable from Makefile */
const uint64_t group_cache_expiration = DSSS_CORRELATION_LENGTH * DSSS_GROUP_CACHE_SIZE;
/* Insert into group cache if space is available or there is a weaker entry to replace */
ssize_t found = group_cache_insertion_index(&st->group, st->group_cache, DSSS_GROUP_CACHE_SIZE);
if (!found)
return; /* Nothing changed */
st->group_cache[found] = st->group;
float mean_phase = 0.0;
for (size_t i=0; i<DSSS_GROUP_CACHE_SIZE; i++)
mean_phase += (st->group_cache[i].max_ts) % DSSS_CORRELATION_LENGTH;
mean_phase /= DSSS_GROUP_CACHE_SIZE;
}
float run_iir(const float x, const int order, const struct iir_biquad q[order], struct iir_biquad_state st[order]) {
float intermediate = x;
for (int i=0; i<(order+1)/2; i++)

33
controller/fw/src/dsss_demod.h
View file

@ -5,6 +5,8 @@
#define DSSS_GOLD_CODE_COUNT ((1<<DSSS_GOLD_CODE_NBITS) + 1)
#define DSSS_CORRELATION_LENGTH (DSSS_GOLD_CODE_LENGTH * DSSS_DECIMATION)
#define PAYLOAD_DATA_BYTE ((PAYLOAD_DATA_BIT+7)/8)
struct iir_biquad {
float a[2];
float b[3];
@ -18,6 +20,24 @@ struct cwt_iir_filter_state {
struct iir_biquad_state st[3];
};
struct {
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 */
} group;
struct decoder_state {
int last_phase;
int candidate_phase;
float last_score;
float candidate_score;
uint8_t data[PAYLOAD_DATA_BYTE];
int data_pos;
};
struct dsss_demod_state {
float signal[DSSS_CORRELATION_LENGTH];
size_t signal_wpos;
@ -27,18 +47,15 @@ struct dsss_demod_state {
struct cwt_iir_filter_state cwt_filter[DSSS_GOLD_CODE_COUNT];
struct {
int len; /* length of group in samples */
float max; /* signed value of largest peak in group on any channel */
int max_idx; /* position of above peak counted from start of group */
int max_ch; /* channel (gold sequence index) of above peak */
} group;
struct group group;
struct group group_cache[DSSS_GROUP_CACHE_SIZE];
};
#ifdef SIMULATION
void dsss_demod_step(struct dsss_demod_state *st, float new_value, size_t sim_pos, int record_channel);
void dsss_demod_step(struct dsss_demod_state *st, float new_value, uint64_t ts, int record_channel);
#else /* SIMULATION */
void dsss_demod_step(struct dsss_demod_state *st, float new_value);
void dsss_demod_step(struct dsss_demod_state *st, float new_value, uint64_t ts);
#endif /* SIMULATION */
#endif /* __DSSS_DEMOD_H__ */