atusb/fw: implemented ATUSB_RESET

- board.c (board_init): disable the watchdog timer (tricky !)
- board.h (reset_cpu), board.c: enable the watchdog timer to cause a
  CPU reset
- ep0.c (my_setup): uncommented and updated ATUSB_RESET handler

atusb/fw/board.c

@@ -61,6 +61,12 @@ void reset_rf(void)
 }
 
 
+void reset_cpu(void)
+{
+	WDTCSR = 1 << WDE;
+}
+
+
 uint8_t read_irq(void)
 {
 	return PIN(IRQ_RF);
@@ -90,6 +96,13 @@ void panic(void)
 
 void board_init(void)
 {
+	/* Disable the watchdog timer */
+
+	MCUSR = 0;		/* Remove override */
+	WDTCSR |= 1 << WDCE;	/* Enable change */
+	WDTCSR = 1 << WDCE;	/* Disable watchdog while still enabling
+				   change */
+
 	/* We start with a 1 MHz/8 clock. Disable the prescaler. */
 
 	CLKPR = 1 << CLKPCE;

atusb/fw/board.h

@@ -63,6 +63,7 @@
 
 
 void reset_rf(void);
+void reset_cpu(void);
 uint8_t read_irq(void);
 
 void led(int on);

atusb/fw/ep0.c

@@ -82,12 +82,10 @@ static int my_setup(const struct setup_request *setup)
 		usb_send(&eps[0], buf+i, size, NULL, NULL);
 		return 1;
 
-#ifdef NOTYET
 	case ATUSB_TO_DEV(ATUSB_RESET):
 		debug("ATUSB_RESET\n");
-		RSTSRC = SWRSF;
+		reset_cpu();
 		while (1);
-#endif
 
 	case ATUSB_TO_DEV(ATUSB_RF_RESET):
 		debug("ATUSB_RF_RESET\n");