mirror of
https://github.com/radio95-rnt/rds95.git
synced 2026-02-27 04:43:52 +01:00
72 lines
1.8 KiB
C
72 lines
1.8 KiB
C
#include "common.h"
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#include "rds.h"
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#include "waveforms.h"
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#include "modulator.h"
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static struct rds_t rds;
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static float waveform[2][FILTER_SIZE];
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static float level;
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void init_rds_objects() {
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level = 1.0f;
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memset(&rds, 0, sizeof(rds));
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for (uint8_t i = 0; i < 2; i++) {
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// This is the bpsk, so waveform[0] is 0 degrees out of phase but waveform[1] is 180 degrees, bpsk
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for (uint16_t j = 0; j < FILTER_SIZE; j++) {
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waveform[i][j] = i ?
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+waveform_biphase[j] : -waveform_biphase[j];
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}
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}
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}
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void set_rds_level(float _level) {
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level = fminf(1.0f, fmaxf(0.0f, _level));
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}
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/* Get an RDS sample. This generates the envelope of the waveform using
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* pre-generated elementary waveform samples.
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*/
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float get_rds_sample() {
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uint16_t idx;
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float *cur_waveform;
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float sample;
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if (rds.sample_count == SAMPLES_PER_BIT) {
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// New Sample
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if (rds.bit_pos == BITS_PER_GROUP) {
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// New bit stream
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get_rds_bits(rds.bit_buffer);
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rds.bit_pos = 0;
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}
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// Differentially encode, so 1111 becomes 1000 and 0001 becomes 0001
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rds.cur_bit = rds.bit_buffer[rds.bit_pos++];
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rds.prev_output = rds.cur_output;
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rds.cur_output = rds.prev_output ^ rds.cur_bit;
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idx = rds.in_sample_index;
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cur_waveform = waveform[rds.cur_output]; // get the waveform, this is the biphase in a 0/180 degree phase shift
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for (uint16_t i = 0; i < FILTER_SIZE; i++) {
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rds.sample_buffer[idx++] += *cur_waveform++;
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if (idx == SAMPLE_BUFFER_SIZE) idx = 0;
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}
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rds.in_sample_index += SAMPLES_PER_BIT;
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if (rds.in_sample_index == SAMPLE_BUFFER_SIZE)
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rds.in_sample_index = 0;
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rds.sample_count = 0;
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}
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rds.sample_count++;
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sample = rds.sample_buffer[rds.out_sample_index];
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rds.sample_buffer[rds.out_sample_index++] = 0;
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if (rds.out_sample_index == SAMPLE_BUFFER_SIZE)
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rds.out_sample_index = 0;
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return sample*level;
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}
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