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Implemented selectable data rates

This commit is contained in:
Mark Qvist 2015-04-26 18:15:05 +02:00
parent 8d9da446a4
commit b3fb6cc35e
2 changed files with 35 additions and 12 deletions
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20
hardware/AFSK.c
View File

@ -340,8 +340,16 @@ void AFSK_adc_isr(Afsk *afsk, int8_t currentSample) {
afsk->iirX[1] = ((int8_t)fifo_pop(&afsk->delayFifo) * currentSample) >> 2;
// The above is a simplification of:
// afsk->iirX[1] = ((int8_t)fifo_pop(&afsk->delayFifo) * currentSample) / 2.899043379;
#elif FILTER_CUTOFF == 1200
afsk->iirX[1] = ((int8_t)fifo_pop(&afsk->delayFifo) * currentSample) >> 1;
// The above is a simplification of:
// afsk->iirX[1] = ((int8_t)fifo_pop(&afsk->delayFifo) * currentSample) / 2.228465666;
#elif FILTER_CUTOFF == 1600
afsk->iirX[1] = ((int8_t)fifo_pop(&afsk->delayFifo) * currentSample) >> 1;
// The above is a simplification of:
// afsk->iirX[1] = ((int8_t)fifo_pop(&afsk->delayFifo) * currentSample) / 1.881349100;
#else
#error Unsupported bitrate!
#error Unsupported filter cutoff!
#endif
afsk->iirY[0] = afsk->iirY[1];
@ -354,8 +362,16 @@ void AFSK_adc_isr(Afsk *afsk, int8_t currentSample) {
afsk->iirY[1] = afsk->iirX[0] + afsk->iirX[1] + (afsk->iirY[0] / 3);
// The above is a simplification of a first-order 800Hz chebyshev filter:
// afsk->iirY[1] = afsk->iirX[0] + afsk->iirX[1] + (afsk->iirY[0] * 0.3101172565);
#elif FILTER_CUTOFF == 1200
afsk->iirY[1] = afsk->iirX[0] + afsk->iirX[1] + (afsk->iirY[0] / 10);
// The above is a simplification of a first-order 800Hz chebyshev filter:
// afsk->iirY[1] = afsk->iirX[0] + afsk->iirX[1] + (afsk->iirY[0] * 0.1025215106);
#elif FILTER_CUTOFF == 1600
afsk->iirY[1] = afsk->iirX[0] + afsk->iirX[1] + -1*(afsk->iirY[0] / 17);
// The above is a simplification of a first-order 800Hz chebyshev filter:
// afsk->iirY[1] = afsk->iirX[0] + afsk->iirX[1] + (afsk->iirY[0] * -0.0630669239);
#else
#error Unsupported bitrate!
#error Unsupported filter cutoff!
#endif

27
hardware/AFSK.h
View File

@ -44,15 +44,20 @@ inline static uint8_t sinSample(uint16_t i) {
#define CONFIG_AFSK_RXTIMEOUT 0
#define CONFIG_AFSK_PREAMBLE_LEN 150UL
#define CONFIG_AFSK_TRAILER_LEN 50UL
#define BIT_STUFF_LEN 5
#define SAMPLERATE 9600
#define BITRATE 1600
#define BITRATE 1200
#define SAMPLESPERBIT (SAMPLERATE / BITRATE)
#define PHASE_INC 1 // Nudge by an eigth of a sample each adjustment
#if BITRATE == 960
#define FILTER_CUTOFF 600
#define MARK_FREQ 1300
#define SPACE_FREQ 2100
#define PHASE_BITS 8 // How much to increment phase counter each sample
#if BITRATE == 1200
#define MARK_FREQ 960
#define SPACE_FREQ 1600
#define PHASE_BITS 10 // How much to increment phase counter each sample
#elif BITRATE == 1200
#define FILTER_CUTOFF 600
#define MARK_FREQ 1200
#define SPACE_FREQ 2200
@ -60,15 +65,17 @@ inline static uint8_t sinSample(uint16_t i) {
#elif BITRATE == 1600
#define FILTER_CUTOFF 800
#define MARK_FREQ 1600
#define SPACE_FREQ 2800
#define PHASE_BITS 6
#define SPACE_FREQ 2600
#define PHASE_BITS 8
#elif BITRATE == 2400
#define FILTER_CUTOFF 1600
#define MARK_FREQ 2400
#define SPACE_FREQ 4200
#define PHASE_BITS 4
#else
#error Unsupported bitrate!
#endif
#define SAMPLESPERBIT (SAMPLERATE / BITRATE)
#define BIT_STUFF_LEN 5
#define PHASE_INC 1 // Nudge by an eigth of a sample each adjustment
#define PHASE_MAX (SAMPLESPERBIT * PHASE_BITS) // Resolution of our phase counter = 64
#define PHASE_THRESHOLD (PHASE_MAX / 2) // Target transition point of our phase window