AVR ExamplePWMgenerator.c

/* ******************************************************** */
/* Example 10.1. Timer counter 1 as a PWM generator         */
/* Modulates LED connected on PB5, SW1 and SW2 changes duty */
/* SW3 and 4 control the red LED                            */
/* Warning: The values are NOT CORRECT, they should be re-  */
/*          placed by students themselves!!!                */
/* ******************************************************** */

#include <avr\io.h>

#define SW1 0
#define SW2 1
#define SW3 2
#define SW4 3

#define RedLED 5

int main(void) {

  /* *********************** Init device MiniMEXLE ******************************** */

    DDRB = 0b00000000;       // PORTB: PWM - PB1, PB2 (LED)  is output, PB6, 7 IN!!!
   PORTB = 0b00000000;       // LED Active low, LED off, No pull-ups

    DDRC = 0b00000000;       // PORTC LED on PC5  is output, SW1-4 are inputs
   PORTC = 0b0000000;       // LED Active high, LED off, pull-ups ON

  /* *********************** Init T1 as a PWM generator *************************** */

  TCCR1A = 0b00000000;       // Mode: PWM, Phase Correct, 9-bit
  TCCR1B = 0b00000000;       // Prescaler 1:1024
   OCR1A = 000;              // Initialization values          
   OCR1B = 000;              // for 1:1 duty cycle
   TCNT1 = 0;           
              

for (;;) {
	      if( bit_is_clear(PINC, SW1)) {  // Switch 1
              OCR1A += 32;                    // Increment OCR
              OCR1B += 32;
              loop_until_bit_is_set(PINC, SW1);
                }
        
	      if(bit_is_clear(PINC, SW2)){   // Switch 2
              OCR1A -= 32;                   // Decrement OCR
  	      OCR1B -= 32;
              loop_until_bit_is_set(PINC, SW2);
                }

              if(bit_is_clear(PINC, SW3)){   // Switch 3
              PORTC |= (1<<RedLED);          // Red LED ON
              loop_until_bit_is_set(PINC, SW3);
                }

              if(bit_is_clear(PINC, SW4)) {  // Switch 4
              PORTC &= ~(1<<RedLED);         // Red LED OFF
 	      loop_until_bit_is_set(PINC, SW4);
                }
          }

}

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