diff options
Diffstat (limited to 'src/disambiguator.c')
| -rw-r--r-- | src/disambiguator.c | 94 |
1 files changed, 81 insertions, 13 deletions
diff --git a/src/disambiguator.c b/src/disambiguator.c index f641834..b93639f 100644 --- a/src/disambiguator.c +++ b/src/disambiguator.c @@ -1,10 +1,54 @@ // (C) 2016 Julian Picht, MIT/x11 License. // -//All MIT/x11 Licensed Code in this file may be relicensed freely under the GPL or LGPL licenses. +// All MIT/x11 Licensed Code in this file may be relicensed freely under the GPL or LGPL licenses. + +// +// The theory behind this disambiguator is, that if we just track all pulses and if one could be a sync pulse, we look back in time, +// if we saw as sync pulse X samples ago than it is probably a sync pulse. +// +// If the skip flag is set, X is 20000 else X is 400000 +// #include "disambiguator.h" #include <stdlib.h> #include <string.h> +#include <stdio.h> + +typedef uint8_t pulse_data; + +/** + * Translate pulse length to pulse SKIP, DATA, AXIS + * @param length Length of the pulse in (1/48000000) seconds + * @return pulse data + */ +pulse_data get_pulse_data(uint32_t length) { + uint16_t temp = length - 2880; + +#if BETTER_SAFE_THAN_FAST + if (temp < 0 || length > 6525) { + return -1; + } +#endif + + if ((temp % 500) < 150) { + return temp / 500; + } + + return -1; +} + +const uint32_t pulse_types[] = { + 0, 1, 0, 1, + 2, 3, 2, 3, +}; + +#define PULSE_BIT_AXIS 0x1 +#define PULSE_BIT_DATA 0x2 +#define PULSE_BIT_SKIP 0x4 + +#define PULSE_DATA(D) ((D >> 1)&0x1) +#define PULSE_AXIS(D) (D&0x01) +#define PULSE_SKIP(D) ((D >> 2)&0x1) void disambiguator_init( struct disambiguator * d ) { memset(&(d->times), 0x0, sizeof(d->times)); @@ -14,9 +58,14 @@ void disambiguator_init( struct disambiguator * d ) { d->max_confidence = 0; } -inline void disambiguator_discard( struct disambiguator * d, long age ); +inline void disambiguator_discard( struct disambiguator * d, uint32_t age ); -void disambiguator_discard( struct disambiguator * d, long age ) +/** + * Drop all data that is outdated + * @param d + * @param age Maximum age of data we care to keep + */ +void disambiguator_discard( struct disambiguator * d, uint32_t age ) { int confidence = 0; for (unsigned int i = 0; i < DIS_NUM_VALUES; ++i) { @@ -32,9 +81,15 @@ void disambiguator_discard( struct disambiguator * d, long age ) d->max_confidence = confidence; } -inline int disambiguator_find_nearest( struct disambiguator * d, long time, int max_diff ); +/** + * Find the index that has the best likelyhood too match up with the timestamp given + * @param time Rising edge time, where we expect to find the last sync pulse + * @param max_diff Maximum difference we are prepared to accept + * @return index inside d->times, if we found something, -1 otherwise + */ +inline int disambiguator_find_nearest( struct disambiguator * d, uint32_t time, int max_diff ); -int disambiguator_find_nearest( struct disambiguator * d, long time, int max_diff ) +int disambiguator_find_nearest( struct disambiguator * d, uint32_t time, int max_diff ) { int diff = max_diff; // max allowed diff for a match int idx = -1; @@ -42,31 +97,44 @@ int disambiguator_find_nearest( struct disambiguator * d, long time, int max_dif if (d->times[i] == 0) continue; int a = abs(d->times[i] - time); + +// printf("T %d %d %d\n", time, i, a); if (a < diff) { idx = i; diff = a; } } + if (idx != -1) { +// printf("R %d %d %d\n", time, idx, d->scores[idx]); + } return idx; } -pulse_type disambiguator_step( struct disambiguator * d, long time, int length) +pulse_type disambiguator_step( struct disambiguator * d, uint32_t time, int length) { + // all smaller pulses are most probably sweeps + // TODO: check we are inside the time window of actual sweeps if (length < 2750) { return d->state == D_STATE_LOCKED ? P_SWEEP : P_UNKNOWN; } - //printf( "%d %d\n", time, length ); - //printf( "." ); - //time -= length/2; - disambiguator_discard(d, time - 10000000); - int idx = disambiguator_find_nearest(d, time - 400000, 100); - + // where to expect the corresponding pulse + uint32_t expected_diff = 400000; + + // we expected to see a sync pulse earlier ... if (time - d->last > 401000) { d->state = D_STATE_UNLOCKED; } + + // discard all data, that is so old, we don't care about it anymore + disambiguator_discard(d, time - 10000000); + + // find the best match for our timestamp and presumed offset + int idx = disambiguator_find_nearest(d, time - expected_diff, 100); + // We did not find a matching pulse, so try find a place to record the current + // one's time of arrival. if (idx == -1) { for (int i = 0; i < DIS_NUM_VALUES; ++i) { if (d->times[i] == 0) { @@ -78,7 +146,7 @@ pulse_type disambiguator_step( struct disambiguator * d, long time, int length) return d->state == D_STATE_LOCKED ? P_SWEEP : P_UNKNOWN; } else { d->scores[idx]++; - if (d->scores[idx] >= 30) { + if (d->scores[idx] >= DIS_NUM_PULSES_BEFORE_LOCK) { d->state = D_STATE_LOCKED; } |