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Mark Qvist 2014-04-03 23:02:57 +02:00
parent 73b8a6ed0b
commit 428e9a0a92
2 changed files with 33 additions and 56 deletions
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87
Modem/afsk.c
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@ -17,28 +17,8 @@
#include <string.h> /* memset */ #include <string.h> /* memset */
#define PHASE_BIT 8 // Sine table for DAC DDS
#define PHASE_INC 1 #define SIN_LEN 512 // Length of a full wave. Table is 1/4 wave.
#define PHASE_MAX (SAMPLESPERBIT * PHASE_BIT)
#define PHASE_THRES (PHASE_MAX / 2)
// Modulator constants
#define MARK_FREQ 1200
#define MARK_INC (uint16_t)(DIV_ROUND(SIN_LEN * (uint32_t)MARK_FREQ, CONFIG_AFSK_DAC_SAMPLERATE))
#define SPACE_FREQ 2200
#define SPACE_INC (uint16_t)(DIV_ROUND(SIN_LEN * (uint32_t)SPACE_FREQ, CONFIG_AFSK_DAC_SAMPLERATE))
//Ensure sample rate is a multiple of bit rate
STATIC_ASSERT(!(CONFIG_AFSK_DAC_SAMPLERATE % BITRATE));
#define DAC_SAMPLESPERBIT (CONFIG_AFSK_DAC_SAMPLERATE / BITRATE)
/**
* Sine table for the first quarter of wave.
* The rest of the wave is computed from this first quarter.
* This table is used to generate the modulated data.
*/
static const uint8_t PROGMEM sin_table[] = static const uint8_t PROGMEM sin_table[] =
{ {
128, 129, 131, 132, 134, 135, 137, 138, 140, 142, 143, 145, 146, 148, 149, 151, 128, 129, 131, 132, 134, 135, 137, 138, 140, 142, 143, 145, 146, 148, 149, 151,
@ -49,43 +29,40 @@ static const uint8_t PROGMEM sin_table[] =
234, 234, 235, 236, 237, 238, 238, 239, 240, 241, 241, 242, 243, 243, 244, 245, 234, 234, 235, 236, 237, 238, 238, 239, 240, 241, 241, 242, 243, 243, 244, 245,
245, 246, 246, 247, 248, 248, 249, 249, 250, 250, 250, 251, 251, 252, 252, 252, 245, 246, 246, 247, 248, 248, 249, 249, 250, 250, 250, 251, 251, 252, 252, 252,
253, 253, 253, 253, 254, 254, 254, 254, 254, 255, 255, 255, 255, 255, 255, 255, 253, 253, 253, 253, 254, 254, 254, 254, 254, 255, 255, 255, 255, 255, 255, 255,
}; }; STATIC_ASSERT(sizeof(sin_table) == SIN_LEN / 4);
#define SIN_LEN 512 ///< Full wave length
STATIC_ASSERT(sizeof(sin_table) == SIN_LEN / 4);
/** // Calculate Sine value from quarter sine table
* Given the index, this function computes the correct sine sample INLINE uint8_t sinSample(uint16_t i) {
* based only on the first quarter of wave. ASSERT(i < SIN_LEN);
*/ uint16_t newI = i % (SIN_LEN/2);
INLINE uint8_t sin_sample(uint16_t idx) newI = (newI >= (SIN_LEN/4)) ? (SIN_LEN/2 - newI -1) : newI;
{ uint8_t sine = pgm_read8(&sin_table[newI]);
ASSERT(idx < SIN_LEN); return (i >= (SIN_LEN/2)) ? (255 - sine) : sine;
uint16_t new_idx = idx % (SIN_LEN / 2);
new_idx = (new_idx >= (SIN_LEN / 4)) ? (SIN_LEN / 2 - new_idx - 1) : new_idx;
uint8_t data = pgm_read8(&sin_table[new_idx]);
return (idx >= (SIN_LEN / 2)) ? (255 - data) : data;
} }
// Look for signal transition. Used for phase sync.
#define BITS_DIFFER(bits1, bits2) (((bits1)^(bits2)) & 0x01)
#define EDGE_FOUND(bits) BITS_DIFFER((bits), (bits) >> 1)
#define BIT_DIFFER(bitline1, bitline2) (((bitline1) ^ (bitline2)) & 0x01) // Phase sync constants
#define EDGE_FOUND(bitline) BIT_DIFFER((bitline), (bitline) >> 1) #define PHASE_BIT 8
#define PHASE_INC 1
#define PHASE_MAX (SAMPLESPERBIT * PHASE_BIT)
#define PHASE_THRES (PHASE_MAX / 2)
/** // Modulation constants
* High-Level Data Link Control parsing function. #define MARK_FREQ 1200
* Parse bitstream in order to find characters. #define MARK_INC (uint16_t)(DIV_ROUND(SIN_LEN * (uint32_t)MARK_FREQ, CONFIG_AFSK_DAC_SAMPLERATE))
* #define SPACE_FREQ 2200
* \param hdlc HDLC context. #define SPACE_INC (uint16_t)(DIV_ROUND(SIN_LEN * (uint32_t)SPACE_FREQ, CONFIG_AFSK_DAC_SAMPLERATE))
* \param bit current bit to be parsed.
* \param fifo FIFO buffer used to push characters. // Check that sample rate is divisible by bitrate
* STATIC_ASSERT(!(CONFIG_AFSK_DAC_SAMPLERATE % BITRATE));
* \return true if all is ok, false if the fifo is full.
*/ #define DAC_SAMPLESPERBIT (CONFIG_AFSK_DAC_SAMPLERATE / BITRATE)
static bool hdlc_parse(Hdlc *hdlc, bool bit, FIFOBuffer *fifo)
static bool hdlcParse(Hdlc *hdlc, bool bit, FIFOBuffer *fifo)
{ {
bool ret = true; bool ret = true;
@ -265,7 +242,7 @@ void afsk_adc_isr(Afsk *af, int8_t curr_sample)
* NRZI coding: if 2 consecutive bits have the same value * NRZI coding: if 2 consecutive bits have the same value
* a 1 is received, otherwise it's a 0. * a 1 is received, otherwise it's a 0.
*/ */
if (!hdlc_parse(&af->hdlc, !EDGE_FOUND(af->found_bits), &af->rx_fifo)) if (!hdlcParse(&af->hdlc, !EDGE_FOUND(af->found_bits), &af->rx_fifo))
af->status |= AFSK_RXFIFO_OVERRUN; af->status |= AFSK_RXFIFO_OVERRUN;
} }
@ -414,7 +391,7 @@ uint8_t afsk_dac_isr(Afsk *af)
af->sample_count--; af->sample_count--;
AFSK_STROBE_OFF(); AFSK_STROBE_OFF();
return sin_sample(af->phase_acc); return sinSample(af->phase_acc);
} }

2
buildrev.h
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@ -1,2 +1,2 @@
#define VERS_BUILD 38 #define VERS_BUILD 45
#define VERS_HOST "vixen" #define VERS_HOST "vixen"