decoding WIP
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jaseg
parent
55ebbcbdbc
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b4d5293d04
5 changed files with 120 additions and 25 deletions
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@ -52,11 +52,14 @@ FMEAS_SAMPLING_RATE ?= 10.0
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DSSS_GOLD_CODE_NBITS ?= 5
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DSSS_DECIMATION ?= 10
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# TODO maybe auto adjust this based on detection rate?
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DSSS_THESHOLD_FACTOR ?= 5.0f
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DSSS_THESHOLD_FACTOR ?= 6.0f
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DSSS_WAVELET_WIDTH ?= 7.3
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DSSS_WAVELET_LUT_SIZE ?= 69
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DSSS_FILTER_FC ?= 3e-3
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DSSS_FILTER_ORDER ?= 12
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DSSS_GROUP_CACHE_SIZE ?= 12
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PAYLOAD_DATA_BIT ?= 64
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CC := $(PREFIX)gcc
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CXX := $(PREFIX)g++
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@ -102,6 +105,8 @@ COMMON_CFLAGS += -DDSSS_DECIMATION=$(DSSS_DECIMATION)
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COMMON_CFLAGS += -DDSSS_THESHOLD_FACTOR=$(DSSS_THESHOLD_FACTOR)
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COMMON_CFLAGS += -DDSSS_WAVELET_WIDTH=$(DSSS_WAVELET_WIDTH)
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COMMON_CFLAGS += -DDSSS_WAVELET_LUT_SIZE=$(DSSS_WAVELET_LUT_SIZE)
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COMMON_CFLAGS += -DDSSS_GROUP_CACHE_SIZE=$(DSSS_GROUP_CACHE_SIZE)
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COMMON_CFLAGS += -DPAYLOAD_DATA_BIT=$(PAYLOAD_DATA_BIT)
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# for musl
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CFLAGS += -Dhidden=
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@ -46,17 +46,16 @@ void debug_print_vector(const char *name, size_t len, const float *data, size_t
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#endif
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#ifdef SIMULATION
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void dsss_demod_step(struct dsss_demod_state *st, float new_value, size_t sim_pos, int record_channel) {
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void dsss_demod_step(struct dsss_demod_state *st, float new_value, uint64_t ts, int record_channel) {
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bool debug = (record_channel == -1)
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&& (sim_pos > 1000)
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&& (sim_pos % DSSS_CORRELATION_LENGTH == DSSS_CORRELATION_LENGTH-1);
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&& (ts > 1000)
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&& (ts % DSSS_CORRELATION_LENGTH == DSSS_CORRELATION_LENGTH-1);
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if (debug) DEBUG_PRINT("Iteration %zd: signal=%f", sim_pos, new_value);
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if (debug) DEBUG_PRINT("Iteration %zd: signal=%f", ts, new_value);
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#else
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void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
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#endif
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//const float peak_group_threshold = 0.05 * DSSS_CORRELATION_LENGTH;
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//const float hole_patching_threshold = 0.01 * DSSS_CORRELATION_LENGTH;
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st->signal[st->signal_wpos] = new_value;
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@ -89,7 +88,7 @@ void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
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float max_val = st->group.max;
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int max_ch = st->group.max_ch;
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int max_idx = st->group.max_idx + 1;
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int max_ts = st->group.max_ts;
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bool found = false;
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for (size_t i=0; i<DSSS_GOLD_CODE_COUNT; i++) {
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float val = cwt[i] / avg[i];
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@ -100,7 +99,7 @@ void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
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if (fabs(val) > fabs(max_val)) {
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max_val = val;
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max_ch = i;
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max_idx = st->group.len;
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max_ts = ts;
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}
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}
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@ -109,7 +108,7 @@ void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
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st->group.len++;
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st->group.max = max_val;
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st->group.max_ch = max_ch;
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st->group.max_idx = max_idx;
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st->group.max_ts = max_ts;
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return;
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}
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@ -120,15 +119,60 @@ void dsss_demod_step(struct dsss_demod_state *st, float new_value) {
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/* A group ended. Process result. */
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if (record_channel == -1)
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DEBUG_PRINT("GROUP FOUND: %8d len=%3d max=%f ch=%d offx=%d",
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sim_pos, st->group.len, st->group.max, st->group.max_ch, st->group.max_idx);
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ts, st->group.len, st->group.max, st->group.max_ch, st->group.max_ts);
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/* reset grouping state */
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st->group.len = 0;
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st->group.max_idx = 0;
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st->group.max_ts = 0;
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st->group.max_ch = 0;
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st->group.max = 0.0f;
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}
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float score_group(const struct group *g, uint64_t ts) {
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return fabs(g->max); /* Possibly at time penalty 1/(ts-max_ts) later */
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}
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ssize_t group_cache_insertion_index(const struct group *g, const struct group *cache, size_t cache_size, uint64_t ts) {
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float min_score = INFINITY;
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ssize_t min_idx = -1;
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for (size_t i=0; i<cache_size; i++) {
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/* If we find an empty or expired entry, use that */
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if (cache[i].max_ts == 0 || ts - cache[i].max_ts > group_cache_expiration)
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return i;
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/* Otherwise check weakest entry */
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float score = score_group(&cache[i]);
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if (score < min_score) {
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min_idx = i;
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min_score = score;
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}
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}
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/* Return weakest group if weaker than candidate */
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if (min_score < score_group(g))
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return min_idx;
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return -1;
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}
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void group_received(struct dsss_demod_state *st, uint64_t ts) {
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/* TODO make these constants configurable from Makefile */
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const uint64_t group_cache_expiration = DSSS_CORRELATION_LENGTH * DSSS_GROUP_CACHE_SIZE;
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/* Insert into group cache if space is available or there is a weaker entry to replace */
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ssize_t found = group_cache_insertion_index(&st->group, st->group_cache, DSSS_GROUP_CACHE_SIZE);
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if (!found)
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return; /* Nothing changed */
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st->group_cache[found] = st->group;
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float mean_phase = 0.0;
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for (size_t i=0; i<DSSS_GROUP_CACHE_SIZE; i++)
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mean_phase += (st->group_cache[i].max_ts) % DSSS_CORRELATION_LENGTH;
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mean_phase /= DSSS_GROUP_CACHE_SIZE;
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}
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float run_iir(const float x, const int order, const struct iir_biquad q[order], struct iir_biquad_state st[order]) {
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float intermediate = x;
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for (int i=0; i<(order+1)/2; i++)
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@ -5,6 +5,8 @@
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#define DSSS_GOLD_CODE_COUNT ((1<<DSSS_GOLD_CODE_NBITS) + 1)
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#define DSSS_CORRELATION_LENGTH (DSSS_GOLD_CODE_LENGTH * DSSS_DECIMATION)
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#define PAYLOAD_DATA_BYTE ((PAYLOAD_DATA_BIT+7)/8)
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struct iir_biquad {
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float a[2];
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float b[3];
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@ -18,6 +20,24 @@ struct cwt_iir_filter_state {
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struct iir_biquad_state st[3];
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};
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struct {
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int len; /* length of group in samples */
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float max; /* signed value of largest peak in group on any channel */
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uint64_t max_ts; /* absolute position of above peak */
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int max_ch; /* channel (gold sequence index) of above peak */
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} group;
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struct decoder_state {
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int last_phase;
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int candidate_phase;
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float last_score;
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float candidate_score;
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uint8_t data[PAYLOAD_DATA_BYTE];
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int data_pos;
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};
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struct dsss_demod_state {
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float signal[DSSS_CORRELATION_LENGTH];
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size_t signal_wpos;
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@ -27,18 +47,15 @@ struct dsss_demod_state {
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struct cwt_iir_filter_state cwt_filter[DSSS_GOLD_CODE_COUNT];
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struct {
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int len; /* length of group in samples */
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float max; /* signed value of largest peak in group on any channel */
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int max_idx; /* position of above peak counted from start of group */
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int max_ch; /* channel (gold sequence index) of above peak */
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} group;
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struct group group;
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struct group group_cache[DSSS_GROUP_CACHE_SIZE];
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};
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#ifdef SIMULATION
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void dsss_demod_step(struct dsss_demod_state *st, float new_value, size_t sim_pos, int record_channel);
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void dsss_demod_step(struct dsss_demod_state *st, float new_value, uint64_t ts, int record_channel);
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#else /* SIMULATION */
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void dsss_demod_step(struct dsss_demod_state *st, float new_value);
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void dsss_demod_step(struct dsss_demod_state *st, float new_value, uint64_t ts);
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#endif /* SIMULATION */
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#endif /* __DSSS_DEMOD_H__ */
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@ -18,11 +18,21 @@ def wrap(left='{', right='}', file=None, end=''):
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def print_include_guards(macro_name):
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print(f'#ifndef {macro_name}')
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print(f'#define {macro_name}')
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print()
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yield
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print()
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print(f'#endif /* {macro_name} */')
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macro_float = lambda f: f'{f}'.replace('.', 'F').replace('-', 'N').replace('+', 'P')
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ordinal = lambda n: "%d%s" % (n,"tsnrhtdd"[(n//10%10!=1)*(n%10<4)*n%10::4])
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SI_TABLE = {-18: 'a', -15: 'f', -12: 'p', -9: 'n', -6: 'µ', -3: 'm', 0: '', 3: 'k', 6: 'M', 9: 'G', 12: 'T', 15: 'P', 18: 'E'}
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def siprefix(x, space=' ', unit=''):
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l = math.log10(x)//3*3
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if l in SI_TABLE:
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return f'{x/10**l}{space}{SI_TABLE[l]}{unit}'
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return f'{x}{space}{unit}'
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if __name__ == '__main__':
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import argparse
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@ -36,10 +46,17 @@ if __name__ == '__main__':
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sos = sig.butter(args.n, args.fc, fs=args.fs, output='sos')
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print('/* THIS IS A GENERATED FILE. DO NOT EDIT! */')
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print()
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with print_include_guards(f'__BUTTER_FILTER_GENERATED_{args.n}_{macro_float(args.fc)}_{macro_float(args.fs)}__'):
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print(f'/* {ordinal(args.n)} order Butterworth IIR filter coefficients')
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print(f' *')
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print(f' * corner frequency f_c = {siprefix(args.fc)}Hz')
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print(f' * sampling rate f_s = {siprefix(args.fs)}Hz')
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print(f' */')
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print()
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print(f'#define {args.macro_name.upper()}_ORDER {args.n}')
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print(f'#define {args.macro_name.upper()}_CLEN {(args.n+1)//2}')
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print(f'#define {args.macro_name.upper()}_COEFF ', end='')
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# scipy.signal.butter by default returns extremely small bs for the first biquad and large ones for subsequent
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# sections. Balance magnitudes to reduce possible rounding errors.
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@ -48,10 +65,14 @@ if __name__ == '__main__':
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mags = [approx_mag // len(sos)] * len(sos)
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mags[0] += approx_mag - sum(mags)
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sos[0][:3] /= 10**approx_mag
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sos = np.array([ sec * np.array([10**mag, 10**mag, 10**mag, 1, 1, 1]) for mag, sec in zip(mags, sos) ])
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for mag, sec in zip(mags, sos):
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ones = np.ones([100000])
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_, steady_state = sig.sosfilt(sos, ones, zi=np.zeros([(args.n+1)//2, 2]))
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print(f'#define {args.macro_name.upper()}_COEFF ', end='')
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for sec in sos:
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bs, ases = sec[:3], sec[4:6]
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bs *= 10**mag
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with wrap():
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print('.b=', end='')
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@ -62,3 +83,11 @@ if __name__ == '__main__':
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print(', '.join(f'{v}' for v in ases), end='')
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print(', ', end='')
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print()
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print(f'#define {args.macro_name.upper()}_STEADY_STATE ', end='')
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for sec in steady_state:
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with wrap():
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print(', '.join(f'{v}' for v in sec), end='')
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print(', ', end='')
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print()
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@ -1178,9 +1178,9 @@
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],
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"metadata": {
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"kernelspec": {
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"display_name": "winlabenv",
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"display_name": "labenv",
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"language": "python",
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"name": "winlabenv"
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"name": "labenv"
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},
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"language_info": {
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"codemirror_mode": {
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@ -1192,7 +1192,7 @@
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.7.6"
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"version": "3.8.1"
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}
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},
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"nbformat": 4,
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