implement synth structure; some test bleeps
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twobit
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34f3aa9e36
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6308e1fe85
241
firmware/synth.c
241
firmware/synth.c
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@ -1,98 +1,245 @@
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#include <inttypes.h>
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#include "freq_table.h"
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// sample rate is 8M / (3 * 64)
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enum { WAVE_PULSE, WAVE_SAW, WAVE_NOISE };
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enum { WAVE_OFF, WAVE_PULSE, WAVE_SAW, WAVE_NOISE };
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enum {
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channel_count = 3,
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tick_length = 600,
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row_length = 4,
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pattern_length = 16
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};
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typedef struct {
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uint8_t wave;
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uint8_t note;
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uint8_t inst_nr;
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uint8_t pos;
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uint16_t phase;
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uint16_t speed;
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uint32_t pulse_width;
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uint8_t pulse_sweep;
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uint16_t pulse_width;
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uint8_t level; // envelop level
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} synth_channel_t;
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typedef struct {
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uint16_t pulse_width;
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uint8_t pulse_sweep;
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uint8_t wave_table_pos;
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uint8_t decay;
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enum {
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synth_channel_count = 2,
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tick_length = 500,
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row_length = 6,
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pattern_length = 16
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} synth_instrument_t;
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static const synth_instrument_t instruments[] = {
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{ 1<<15, 255, 8 },
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{ 0, 255, 8 },
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{ 0, 0, 5 },
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{ 1<<14, 0, 0, 3 },
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{ 1<<14, 0, 10, 3 },
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};
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typedef struct {
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synth_channel_t channels[synth_channel_count];
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static const uint8_t wave_table[][2] = {
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{ 0, WAVE_PULSE },
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{ 3, WAVE_PULSE },
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{ 7, WAVE_PULSE },
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{ 12, WAVE_PULSE },
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{ 256 - 4, 0xff },
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int16_t sample;
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int8_t tick;
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int8_t row;
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int8_t seq;
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{ 0, WAVE_NOISE },
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{ 0, WAVE_SAW },
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{ 0xff, 0xff },
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} synth_t;
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{ 0, WAVE_PULSE },
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{ 0xff, 0xff },
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static synth_t synth;
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{ 0, WAVE_PULSE },
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{ 2, WAVE_PULSE },
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{ 7, WAVE_PULSE },
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{ 10, WAVE_PULSE },
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{ 256 - 4, 0xff },
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};
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static const uint8_t patterns[][pattern_length][2] = {
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{
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{ 33 - 12, 0 },
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{ 0xff, 1 },
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{ 33 - 12, 1 },
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{ 0xff, 1 },
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{ 33, 1 },
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{ 0xff, 1 },
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{ 33, 1 },
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{ 0xff, 1 },
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{ 33, 1 },
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{ 0xff, 1 },
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{ 33 - 12, 1 },
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{ 0xff, 1 },
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{ 33 - 12, 1 },
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{ 0xff, 1 },
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{ 33, 1 },
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{ 0xff, 1 },
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},
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{
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{ 28 - 12, 0 },
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{ 0xff, 1 },
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{ 28 - 12, 1 },
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{ 0xff, 1 },
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{ 28, 1 },
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{ 0xff, 1 },
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{ 28, 1 },
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{ 0xff, 1 },
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{ 28, 1 },
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{ 0xff, 1 },
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{ 28 - 12, 1 },
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{ 0xff, 1 },
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{ 28 - 12, 1 },
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{ 0xff, 1 },
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{ 28, 1 },
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{ 0xff, 1 },
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},
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{
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{ 69, 2 },
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{ 0, 0 },
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{ 57 - 24, 2 },
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{ 0, 0 },
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{ 0xff, 0 },
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{ 45, 2 },
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{ 0, 0 },
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{ 0xff, 0 },
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{ 45+3, 2 },
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{ 0, 0 },
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{ 45+7, 2 },
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{ 0, 0 },
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{ 0xff, 0 },
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},
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{
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{ 0, 0 },
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{ 0, 0 },
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{ 0, 0 },
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{ 0, 0 },
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{ 57, 3 },
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},
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{
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{ 0, 0 },
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{ 0, 0 },
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{ 0, 0 },
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{ 0, 0 },
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{ 57, 4 },
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}
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};
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static const uint8_t pattern_table[][channel_count] = {
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{ 0, 2, 3 },
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{ 0, 2, 3 },
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{ 0, 2, 3 },
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{ 0, 2, 3 },
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{ 1, 2, 4 },
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{ 1, 2, 4 },
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{ 1, 2, 4 },
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{ 1, 2, 4 },
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};
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enum {
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pattern_table_length = sizeof(pattern_table) / sizeof(pattern_table[0])
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};
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static synth_channel_t channels[channel_count];
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static int16_t sample;
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static int8_t tick;
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static int8_t row;
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static int8_t seq;
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void synth_init(void)
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{
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// some test values
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synth.channels[0].wave = WAVE_PULSE;
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synth.channels[0].speed = 1153;
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synth.channels[0].pulse_sweep = 0;
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synth.channels[0].pulse_width = 1 << 31;
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sample = 0;
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tick = 0;
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row = 0;
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seq = 0;
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synth.channels[1].wave = WAVE_SAW;
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synth.channels[1].speed = 1728;
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/*
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// some test values
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channels[0].wave = WAVE_PULSE;
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channels[0].pulse_width = 1 << 15;
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channels[1].wave = WAVE_SAW;
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*/
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}
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uint16_t synth_mix(void)
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{
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if(synth.sample == 0) {
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// new tick
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if(synth.tick == 0) {
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// new row
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if(synth.row == 0) {
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// new pattern
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if(sample == 0) { // new tick
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for(int i = 0; i < channel_count; i++) {
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synth_channel_t* chan = &channels[i];
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const synth_instrument_t* inst = &instruments[chan->inst_nr];
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if(chan->level > inst->decay) chan->level -= inst->decay;
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else chan->level = 0;
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chan->pulse_width += inst->pulse_sweep;
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chan->pos++;
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if(wave_table[chan->pos][1] == 0xff) chan->pos += wave_table[chan->pos][0];
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// enter new row
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if(tick == 0) {
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uint8_t pattern_nr = pattern_table[seq][i];
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uint8_t note = patterns[pattern_nr][row][0];
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if(note) { // new note, maybe?
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if(note == 0xff) {
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chan->level = 0;
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} else {
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chan->level = 100;
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chan->note = note;
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chan->inst_nr = patterns[pattern_nr][row][1];
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inst = &instruments[chan->inst_nr];
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chan->pos = inst->wave_table_pos;
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if(inst->pulse_width) chan->pulse_width = inst->pulse_width;
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}
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}
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}
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}
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}
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if(++synth.sample == tick_length) {
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synth.sample = 0;
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if(++synth.tick == row_length) {
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synth.tick = 0;
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if(++synth.row == pattern_length) {
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synth.row = 0;
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if(++sample == tick_length) {
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sample = 0;
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if(++tick == row_length) {
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tick = 0;
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if(++row == pattern_length) {
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row = 0;
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if(++seq == pattern_table_length) {
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seq = 0;
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}
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}
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}
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}
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uint16_t output = 0;
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for(int i = 0; i < synth_channel_count; i++) {
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synth_channel_t *chan = &synth.channels[i];
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for(int i = 0; i < channel_count; i++) {
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synth_channel_t* chan = &channels[i];
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const synth_instrument_t* inst = &instruments[chan->inst_nr];
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chan->phase += chan->speed;
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chan->pulse_width += chan->pulse_sweep << 8;
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chan->phase += freq_table[chan->note + wave_table[chan->pos][0]];
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uint8_t amp;
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switch(chan->wave) {
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switch(wave_table[chan->pos][1]) {
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case WAVE_PULSE:
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amp = -(chan->phase < (chan->pulse_width >> 16));
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amp = -(chan->phase < chan->pulse_width);
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break;
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case WAVE_SAW:
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amp = (chan->phase >> 8);
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break;
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case WAVE_NOISE: // shitty noise
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case WAVE_NOISE: // shitty noise
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chan->phase = (chan->phase >> 1) ^ (-(chan->phase & 1) & 0xb400);
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amp = (chan->phase >> 8);
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break;
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@ -102,7 +249,7 @@ uint16_t synth_mix(void)
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break;
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}
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output += (amp & 0xff) / 2;
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output += ((amp & 0xff) * chan->level) >> 8;
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}
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return output;
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