implement synth structure; some test bleeps

firmware/synth.c

@@ -1,91 +1,238 @@
 #include <inttypes.h>
+#include "freq_table.h"
 // sample rate is 8M / (3 * 64)
 
 
-enum { WAVE_PULSE, WAVE_SAW, WAVE_NOISE };
+enum {  WAVE_OFF, WAVE_PULSE, WAVE_SAW, WAVE_NOISE };
+enum {
+	channel_count = 3,
+	tick_length = 600,
+	row_length = 4,
+	pattern_length = 16
+};
 
 typedef struct {
-	uint8_t	wave;
+	uint8_t	note;
+	uint8_t	inst_nr;
+	uint8_t pos;
 
 	uint16_t phase;
-	uint16_t speed;
+	uint16_t pulse_width;
-
-	uint32_t pulse_width;
-	uint8_t pulse_sweep;
 
 	uint8_t	level;			// envelop level
 
 } synth_channel_t;
 
 
+typedef struct {
+	uint16_t	pulse_width;
+	uint8_t		pulse_sweep;
+	uint8_t		wave_table_pos;
+	uint8_t		decay;
 
-enum {
+} synth_instrument_t;
-	synth_channel_count = 2,
+
-	tick_length = 500,
+
-	row_length = 6,
+static const synth_instrument_t instruments[] = {
-	pattern_length = 16
+	{ 1<<15, 255, 8 },
+	{ 0, 255, 8 },
+	{ 0, 0, 5 },
+	{ 1<<14, 0, 0, 3 },
+	{ 1<<14, 0, 10, 3 },
 };
 
-typedef struct {
+static const uint8_t wave_table[][2] = {
-	synth_channel_t channels[synth_channel_count];
+	{  0, WAVE_PULSE },
+	{  3, WAVE_PULSE },
+	{  7, WAVE_PULSE },
+	{  12, WAVE_PULSE },
+	{  256 - 4, 0xff },
 
-	int16_t sample;
+	{  0, WAVE_NOISE },
-	int8_t tick;
+	{  0, WAVE_SAW },
-	int8_t row;
+	{  0xff, 0xff },
-	int8_t seq;
 
-} synth_t;
+	{  0, WAVE_PULSE },
+	{  0xff, 0xff },
 
-static synth_t synth;
+	{  0, WAVE_PULSE },
+	{  2, WAVE_PULSE },
+	{  7, WAVE_PULSE },
+	{  10, WAVE_PULSE },
+	{  256 - 4, 0xff },
+};
 
 
+static const uint8_t patterns[][pattern_length][2] = {
+	{
+		{   33 - 12, 0 },
+		{ 0xff, 1 },
+		{   33 - 12, 1 },
+		{ 0xff, 1 },
+		{   33, 1 },
+		{ 0xff, 1 },
+		{   33, 1 },
+		{ 0xff, 1 },
+		{   33, 1 },
+		{ 0xff, 1 },
+		{   33 - 12, 1 },
+		{ 0xff, 1 },
+		{   33 - 12, 1 },
+		{ 0xff, 1 },
+		{   33, 1 },
+		{ 0xff, 1 },
+	},
+	{
+		{   28 - 12, 0 },
+		{ 0xff, 1 },
+		{   28 - 12, 1 },
+		{ 0xff, 1 },
+		{   28, 1 },
+		{ 0xff, 1 },
+		{   28, 1 },
+		{ 0xff, 1 },
+		{   28, 1 },
+		{ 0xff, 1 },
+		{   28 - 12, 1 },
+		{ 0xff, 1 },
+		{   28 - 12, 1 },
+		{ 0xff, 1 },
+		{   28, 1 },
+		{ 0xff, 1 },
+	},
+	{
+		{   69, 2 },
+		{    0, 0 },
+		{   57 - 24, 2 },
+		{    0, 0 },
+		{ 0xff, 0 },
+		{   45, 2 },
+		{    0, 0 },
+		{ 0xff, 0 },
+		{   45+3, 2 },
+		{    0, 0 },
+		{   45+7, 2 },
+		{    0, 0 },
+		{ 0xff, 0 },
+	},
+	{
+		{   0, 0 },
+		{   0, 0 },
+		{   0, 0 },
+		{   0, 0 },
+		{   57, 3 },
+	},
+	{
+		{   0, 0 },
+		{   0, 0 },
+		{   0, 0 },
+		{   0, 0 },
+		{   57, 4 },
+	}
+
+};
+
+static const uint8_t pattern_table[][channel_count] = {
+	{ 0, 2, 3 },
+	{ 0, 2, 3 },
+	{ 0, 2, 3 },
+	{ 0, 2, 3 },
+	{ 1, 2, 4 },
+	{ 1, 2, 4 },
+	{ 1, 2, 4 },
+	{ 1, 2, 4 },
+};
+enum {
+	pattern_table_length = sizeof(pattern_table) / sizeof(pattern_table[0])
+};
+
+
+static synth_channel_t channels[channel_count];
+static int16_t sample;
+static int8_t tick;
+static int8_t row;
+static int8_t seq;
+
 
 void synth_init(void)
 {
-	// some test values
+	sample = 0;
-	synth.channels[0].wave = WAVE_PULSE;
+	tick = 0;
-	synth.channels[0].speed = 1153;
+	row = 0;
-	synth.channels[0].pulse_sweep = 0;
+	seq = 0;
-	synth.channels[0].pulse_width = 1 << 31;
 
-	synth.channels[1].wave = WAVE_SAW;
+/*
-	synth.channels[1].speed = 1728;
+	// some test values
+	channels[0].wave = WAVE_PULSE;
+	channels[0].pulse_width = 1 << 15;
+
+	channels[1].wave = WAVE_SAW;
+*/
 }
 
 uint16_t synth_mix(void)
 {
-	if(synth.sample == 0) {
+	if(sample == 0) { // new tick
-		// new tick
+		for(int i = 0; i < channel_count; i++) {
-		if(synth.tick == 0) {
+			synth_channel_t* chan = &channels[i];
-			// new row
+
-			if(synth.row == 0) {
+			const synth_instrument_t* inst = &instruments[chan->inst_nr];
-				// new pattern
+
+			if(chan->level > inst->decay) chan->level -= inst->decay;
+			else chan->level = 0;
+
+			chan->pulse_width += inst->pulse_sweep;
+
+
+			chan->pos++;
+			if(wave_table[chan->pos][1] == 0xff) chan->pos += wave_table[chan->pos][0];
+
+
+			// enter new row
+			if(tick == 0) {
+				uint8_t pattern_nr = pattern_table[seq][i];
+				uint8_t note = patterns[pattern_nr][row][0];
+
+				if(note) { // new note, maybe?
+					if(note == 0xff) {
+						chan->level = 0;
+					} else {
+						chan->level = 100;
+						chan->note = note;
+						chan->inst_nr = patterns[pattern_nr][row][1];
+						inst = &instruments[chan->inst_nr];
+						chan->pos = inst->wave_table_pos;
+						if(inst->pulse_width) chan->pulse_width = inst->pulse_width;
 					}
 				}
 			}
-	if(++synth.sample == tick_length) {
+		}
-		synth.sample = 0;
+	}
-		if(++synth.tick == row_length) {
+	if(++sample == tick_length) {
-			synth.tick = 0;
+		sample = 0;
-			if(++synth.row == pattern_length) {
+		if(++tick == row_length) {
-				synth.row = 0;
+			tick = 0;
+			if(++row == pattern_length) {
+				row = 0;
+				if(++seq == pattern_table_length) {
+					seq = 0;
+				}
 			}
 		}
 	}
 
 
 	uint16_t output = 0;
-	for(int i = 0; i < synth_channel_count; i++) {
+	for(int i = 0; i < channel_count; i++) {
-		synth_channel_t *chan = &synth.channels[i];
+		synth_channel_t* chan = &channels[i];
+		const synth_instrument_t* inst = &instruments[chan->inst_nr];
 
-
+		chan->phase += freq_table[chan->note + wave_table[chan->pos][0]];
-		chan->phase += chan->speed;
-		chan->pulse_width += chan->pulse_sweep << 8;
 
 		uint8_t amp;
-		switch(chan->wave) {
+		switch(wave_table[chan->pos][1]) {
 		case WAVE_PULSE:
-			amp = -(chan->phase < (chan->pulse_width >> 16));
+			amp = -(chan->phase < chan->pulse_width);
 			break;
 
 		case WAVE_SAW:
@@ -102,7 +249,7 @@ uint16_t synth_mix(void)
 			break;
 		}
 
-		output += (amp & 0xff) / 2;
+		output += ((amp & 0xff) * chan->level) >> 8;
 	}
 
 	return output;