Work in Progress

tinyhacks-007-sleep/main.c

@@ -1,4 +1,4 @@
-// Blink2313 - Blink a LED on PD5 of a ATTiny 2313
+// tinyhacks-007-sleep/main.c
 
 #include <avr/io.h>
 #include <avr/delay.h>
@@ -9,34 +9,37 @@ volatile uint8_t count = 0;
 
 ISR(INT0_vect)
 {
+    // Disable the INT0 interrupt to prevent it from firing before we are ready to handle it again
     GIMSK &= ~(1 << INT0);
+    // Increment our interrupt counter
     count++;
 }
 
 int main(void)
 {
+    // PB0 is connected to a LED
     DDRB |= (1 << PB0);
-    MCUCR &= ~(1 << ISC00);
-    MCUCR &= ~(1 << ISC01);
+
+    // Disable all internal systems during power down mode
     PRR = (1 << PRTIM1) | (1 << PRTIM0) | (1 << PRUSI) | (1 << PRADC);
 
     sei();
 
     while (1)
     {
-        // Sleep
+        GIMSK |= (1 << INT0); // This needs to be before the sleep instruction
+
+        // Sleep in power down mode. Before we sleep we enable the INT0 interrupt.
 
         set_sleep_mode(SLEEP_MODE_PWR_DOWN);
         sleep_enable();
-        GIMSK |= (1 << INT0);
         sleep_cpu();
 
         // If we have been woken up 4 times then it is time to do 'work'
 
-        if (count == 4)
+        if (count >= 4)
         {
             // Flash the led three times
-
             for (uint8_t i = 0; i < 3; i++) {
                 PORTB |= (1 << PB0);
                 _delay_ms(50);
@@ -45,7 +48,6 @@ int main(void)
             }
 
             // Reset the counter
-
             count = 0;
         }