button pwm

btn-pwm/main.c

@@ -0,0 +1,57 @@
+/*
+ * Use the timers pwm to dim a light on demand.
+ */
+#define F_CPU 16000000UL
+#define __AVR_ATmega328P__
+#include <avr/interrupt.h>
+#include <avr/io.h>
+#include <util/delay.h>
+
+#define PWM_LOW 24
+#define PWM_HIGH 192
+
+int state = 0;
+
+// code for INT0
+ISR(INT0_vect) {
+  OCR0A = PWM_HIGH;              // max value for timer
+  PORTB |= (1<<PORTB5);
+}
+
+// code for INT1
+ISR(INT1_vect) {
+  OCR0A = PWM_LOW;              // max value for timer
+  PORTB &= ~(1<<PORTB5);
+}
+
+int main(void) {
+
+  // read from D2 and D3, write to D6
+  DDRD |= (1 << PORTD6);
+  DDRB = 0xff; // used for internal led only
+
+  PORTD |= (1 << PORTD2) | (1 << PORTD3); // pull up D2 and D3
+
+  // enable external interruprs
+  EIMSK |= (1 << INT0);
+  EIMSK |= (1 << INT1);
+
+  // trigger when anything changes
+  EICRA |= (1 << ISC00); // for INT0
+  EICRA |= (1 << ISC10); // for INT1
+
+  // Timer 0
+  // Mode: Fast PWM
+  // Prescaler: /8
+  // max: dynamic depending on pushed button
+  TCCR0A |= (1 << WGM01) | (1 << WGM00);  // Fast PWM Mode
+  OCR0A = PWM_HIGH;   // max value for timer
+  TCCR0A |= (1 << COM0A1); // set non inverting mode, start initialized
+
+  TCCR0B |= (1 << CS01); // enable with prescaler 8
+
+  sei(); // magic interrupt macro
+  while (1) {
+    // do nothing
+  }
+}

buttons/main.c

@@ -18,7 +18,6 @@ int main(void) {
   DDRD = 0;    // read from D
 
   PORTD |= (1 << PORTD2) | (1 << PORTD3); // pull up D2 and D3
-
   PORTB = 0;
 
   // enable external interruprs