diff --git a/firmware/Makefile b/firmware/Makefile
index f0bdf36..9a0f19f 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -35,7 +35,7 @@ OPT = s
 
 ##########################################################################################################
 # List C source files here. (C dependencies are automatically generated.)
-SRC	= main.c 
+SRC	= main.c synth.c
 ##########################################################################################################
 
 
diff --git a/firmware/synth.c b/firmware/synth.c
index de0970d..1d56611 100644
--- a/firmware/synth.c
+++ b/firmware/synth.c
@@ -4,13 +4,26 @@
 
 
 enum {
-	synth_channel_count = 2
+	synth_channel_count = 2,
 };
 
+enum {
+	WAVE_PULSE,
+	WAVE_SAW,
+};
+
+
 typedef struct {
+	uint8_t	wave;
+
 	uint16_t phase;
 	uint16_t speed;
 
+	uint32_t pulse_width;
+	uint8_t pulse_sweep;
+
+	uint8_t	level;			// envelop level
+
 } synth_channel_t;
 
 typedef struct {
@@ -20,24 +33,47 @@ typedef struct {
 static synth_t synth;
 
 
+
 void synth_init(void)
 {
 	// some test values
-	synth.channels[0].phase = 0;
+	synth.channels[0].wave = WAVE_PULSE;
 	synth.channels[0].speed = 1153;
+	synth.channels[0].pulse_sweep = 0;
+	synth.channels[0].pulse_width = 1 << 31;
 
-	synth.channels[1].phase = 0;
+	synth.channels[1].wave = WAVE_SAW;
 	synth.channels[1].speed = 1728;
+
 }
 
 uint16_t synth_mix(void)
 {
 	uint16_t output = 0;
 
-	for (int i = 0; i < synth_channel_count; i++) {
+	for(int i = 0; i < synth_channel_count; i++) {
 		synth_channel_t *chan = &synth.channels[i];
+
+
 		chan->phase += chan->speed;
-		output += ((chan->phase >> 8) & 0xff) / 2;
+		chan->pulse_width += chan->pulse_sweep << 8;
+
+		uint8_t amp;
+		switch(chan->wave) {
+		case WAVE_PULSE:
+			amp = -(chan->phase < (chan->pulse_width >> 16));
+			break;
+
+		case WAVE_SAW:
+			amp = (chan->phase >> 8);
+			break;
+
+		default:
+			amp = 0;
+			break;
+		}
+
+		output += (amp & 0xff) / 2;
 	}
 
 	return output;