start synth implementation

firmware/Makefile

@@ -60,7 +60,7 @@ EXTRAINCDIRS =
 #  -Wall...:  warning level
 #  -Wa,...:   tell GCC to pass this to the assembler.
 #    -ahlms:  create assembler listing
-CFLAGS  = -O$(OPT)
+CFLAGS  = -O$(OPT) -g
 CFLAGS += -funsigned-char
 CFLAGS += -funsigned-bitfields
 CFLAGS += -fpack-struct

firmware/main.c

@@ -6,6 +6,55 @@
 
 #include "main.h"
 
+
+// sample rate is 8M / (5 * 64) = 25000
+
+enum {
+	synth_channel_count = 2
+};
+
+typedef struct {
+	uint16_t phase;
+	uint16_t speed;
+
+} synth_channel_t;
+
+typedef struct {
+	synth_channel_t channels[synth_channel_count];
+	uint16_t output;
+} synth_t;
+
+
+static synth_t synth;
+
+static void synth_init(void)
+{
+	// some test values
+	synth.channels[0].phase = 0;
+	synth.channels[0].speed = 1153;
+
+	synth.channels[1].phase = 0;
+	synth.channels[1].speed = 23456;
+}
+
+
+static inline void synth_mix(void)
+{
+	synth.output = 0;
+
+	for(int i = 0; i < synth_channel_count; i++) {
+		synth_channel_t* chan = &synth.channels[i];
+		chan->phase += chan->speed;
+
+		synth.output += (chan->phase >> 16) & 0xff;
+	}
+}
+
+
+
+
+
+
 static inline void init_pwm(void)
 {
 	//PB1 set to output:
@@ -46,13 +95,13 @@ static void stupid_pwmtest(void)
 {
 	uint8_t i, t, r;
 	ICR1 = 0xAA00;
-		r=1;
+	t = r = 1;
 	for (;;) {
 
 		t = (r) ? (t+1) : (t-1);
 
 		ICR1 = (t << 7);
-		if(t=0) r ^= 1;
+		if(t == 0) r ^= 1;
 		for(i = 1; i < 100; i++) __asm("nop");
 
 
@@ -70,9 +119,11 @@ int main(void)
 	init_motor();
 	init_pwm();
 
+	synth_init();
+
 	//just stupid test for now....
 	stupid_pwmtest();
 
 	//never get here
-	return;
+	return 0;
 }