enum for btn-pwm-ctrl

btn-pwm-ctrl/main.c

@@ -0,0 +1,85 @@
+/*
+ * Use the timers pwm to dim a light on demand.
+ * The light will change continously until you
+ * press the button to stop.
+ */
+#define F_CPU 16000000UL
+#define __AVR_ATmega328P__
+#include <avr/interrupt.h>
+#include <avr/io.h>
+#include <util/delay.h>
+
+#define PWM_LOW 0
+#define PWM_HIGH 96
+#define DELAY 25
+
+void change();
+
+typedef enum {
+  UP,
+  STOP,
+  DOWN
+} State;
+State state = UP;
+int brightness = PWM_HIGH;
+
+// code for INT0
+ISR(INT0_vect) {
+  PORTB |= (1 << PORTB5);
+  state = UP;
+}
+
+// code for INT1
+ISR(INT1_vect) {
+  PORTB &= ~(1 << PORTB5);
+  state = STOP;
+}
+
+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 = brightness;                    // max value for timer
+  TCCR0A |= (1 << COM0A1); // set non inverting mode, start initialized
+
+  TCCR0B |= (1 << CS02) | (1 << CS00); // enable with prescaler 1024
+
+  sei(); // magic interrupt macro
+  while (1) {
+    change();
+    _delay_ms(DELAY);
+  }
+}
+
+void change() {
+  // start looping through brightnesses
+  if (state == UP) {
+    OCR0A = brightness++;
+    if (brightness >= PWM_HIGH) {
+      state = DOWN;
+    }
+  }
+  if (state == DOWN) {
+    OCR0A = brightness--;
+    if (brightness <= PWM_LOW) {
+      state = UP;
+    }
+  }
+}