diff --git a/src/Makefile b/src/Makefile
index 9510eb8..ac5ab0c 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -27,7 +27,8 @@ CC=avr-gcc -Wall -Wno-parentheses -MMD -std=c99 -O3 \
   -fpack-struct \
   -fshort-enums \
   -mtiny-stack \
-  -mint8
+  -mint8 \
+  -fverbose-asm
 
 SN = $(SN_$(PROJ))
 CFLAGS = $($*_CFLAGS) $(DEBUG) -I. -DSN="$(SN)"
diff --git a/src/blink.c b/src/blink.c
index 5970d8c..4e25198 100644
--- a/src/blink.c
+++ b/src/blink.c
@@ -9,77 +9,126 @@
 #include <avr/interrupt.h>
 #include <avr/sleep.h>
 
+#define Bit(x) (1<<(x))
+#define SetPORT(x) PORTB |= Bit(x)
+#define ClrPORT(x) PORTB &=~ Bit(x)
+#define GetPORT(x) (PINB & Bit(x))
+
 #define RES_PORT  0
 #define TRIG_PORT 1
 #define OUT_PORT  2
 #define LED2_PORT 3
 #define LED1_PORT 4
 
-uint8_t tick;
+#define START_PORT OUT_PORT
+
+// 9.6MHz/8/240 = 5kHz
+#define MAX_DC 240
+#define DC_EXP 12
+
+static uint32_t led1_dc;
+
+static inline
+uint8_t get_dc(uint32_t dc) {
+	return dc >> 24;
+}
+static inline
+uint32_t set_dc(uint8_t dc) {
+	return ((uint32_t)dc << 24) - 1;
+}
+static inline
+uint32_t fade(uint32_t dc)
+{
+	uint32_t diff = dc >> (8*((DC_EXP+4)>>3));
+	if (DC_EXP & 4)
+		diff <<= 8 - (DC_EXP&7);
+	else
+		diff >>= DC_EXP & 3;
+	return dc - diff;
+}
 
 ISR(TIM0_COMPB_vect)
 {
-	PORTB |= 1 << LED2_PORT;
+	SetPORT(LED1_PORT);
 }
 
 ISR(TIM0_COMPA_vect)
 {
-	PORTB &=~ (1 << LED2_PORT);
-	TIFR0 = (1<<OCF0B);
-	tick = 1;
+	TIFR0 = Bit(OCF0B);
+	ClrPORT(LED1_PORT);
+	OCR0B = MAX_DC + 1 - (uint8_t)(led1_dc >> 24);
 }
 
-void set_dc(uint8_t dc)
+static inline
+void pulse_led1(uint8_t dc)
 {
-	OCR0B = 255 - dc;
-}
-
-uint8_t get_dc()
-{
-	return 255 - OCR0B;
+	led1_dc = set_dc(dc);
+	OCR0B = MAX_DC + 1 - dc;
 }
 
 static inline
 void init_timer()
 {
-	DDRB = (1<<LED1_PORT) | (1<<LED2_PORT);
+	DDRB = Bit(LED1_PORT) | Bit(LED2_PORT);
+	ClrPORT(LED1_PORT);
 	TCCR0A = 0x02; // CTC TOP=OCRA TOV=MAX
 	TCCR0B = 0x02; // clk_IO/8
-	OCR0A  = 254;
-	set_dc(10);
-	TIMSK0 = (1<<OCIE0A) | (1<<OCIE0B);
+	OCR0A  = MAX_DC;
+	OCR0B  = 255;  // off
+	TIMSK0 = Bit(OCIE0A) | Bit(OCIE0B);
 }
 
-static const uint8_t nticks = 50;
+ISR(PCINT0_vect)
+{
+	SetPORT(LED2_PORT);
+	if (!GetPORT(START_PORT))
+		pulse_led1(MAX_DC);
+	ClrPORT(LED2_PORT);
+}
+
+static inline
+void init_trig()
+{
+	PCMSK = Bit(START_PORT);
+	GIMSK = Bit(PCIE);
+}
+
+
+void init_wdt(uint8_t wdt_period)
+{
+#ifdef WDT_TRIGGERED
+        uint8_t cr = Bit(WDE) | (wdt_period&7) << WDP0 | (wdt_period&8) << (WDP3-3);
+        __asm__("STS %[CSR], %[CE]"     "\n\t"
+                "STS %[CSR], %[WE]"     "\n"
+                ::[CSR] "n" (&WDTCR),
+                 [CE] "r" ((Bit(WDCE) | Bit(WDE))),
+                 [WE] "r" (cr)
+                );
+#endif // WDT_TRIGGERED
+}
 
 int main()
 {
 	init_timer();
+	init_trig();
+	pulse_led1(MAX_DC);
+	init_wdt(7);
 	set_sleep_mode(SLEEP_MODE_IDLE);
-	uint8_t n = 0;
+	uint16_t debug = 0;
 	while (1) {
+		if (!debug) { 
+			// debug = 0xff00L | OCR0B;
+			ClrPORT(LED2_PORT);
+		}
+		else {
+			if (debug&1)
+				SetPORT(LED2_PORT);
+			else
+				ClrPORT(LED2_PORT);
+			debug >>= 1;
+		}
 		sei();
 		sleep_mode();
-
-		if (PINB & (1 << TRIG_PORT))
-			PORTB &=~ (1 << LED1_PORT);
-		else
-			PORTB |= (1 << LED1_PORT);
-
-		uint8_t dc = get_dc();
-
-		if (dc == 0 && !(PINB & (1 << OUT_PORT)))
-			set_dc(255);
-
-		if (tick) {
-			tick = 0;
-			n = n - 1;
-			if (n == 0) {
-				n = nticks;
-				if (dc)
-					set_dc(dc-1);
-			}
-		}
-
+		led1_dc = fade(led1_dc);
 	}
 }