1. #define F_CPU 8000000UL
  2.  
  3. #include <avr/io.h>
  4. #include <avr/interrupt.h>
  5. #include <util/delay.h>
  6. #include <compat/deprecated.h>
  7.  
  8. void initialize(void);
  9.  
  10. //functions for left wheel
  11. void init_pwm_right(void);
  12. void start_pwm_right(void);
  13. void stop_pwm_right(void);
  14.  
  15. //functions for right wheel
  16. void init_pwm_left(void);
  17. void start_pwm_left(void);
  18. void stop_pwm_left(void);
  19.  
  20.  
  21. int main(void)
  22. {
  23.     volatile int i = 0, j = 0, k = 0;
  24.     initialize();  //call initialize routine, rest would be done by interrupts.
  25.  
  26.     while(1)       //main loop for LFR
  27.     {
  28.  
  29.         i = bit_is_set(PINB, PB0);
  30.         if(!i)
  31.         {
  32.             //Steer to left
  33.             stop_pwm_left();
  34.             stop_pwm_right();
  35.             start_pwm_right();
  36.         }
  37.         else
  38.         {
  39.             //Steer to right
  40.             stop_pwm_left();
  41.             stop_pwm_right();
  42.             start_pwm_left();
  43.         }  
  44.  
  45.         // Some delay
  46.         for(j=0;j<255;j++)
  47.         {
  48.             for(k=0;k<255;k++)
  49.             {
  50.             }
  51.         }
  52.     }  
  53. }
  54.  
  55. void initialize()
  56. {
  57.     init_pwm_left();
  58.     init_pwm_right();
  59.  
  60.     start_pwm_left();
  61.     start_pwm_right();
  62.  
  63.     DDRB |= (0 << DDB0);   //setting PORTB.0 as input
  64. }
  65.  
  66. void init_pwm_right(void)
  67. {
  68.     TCCR2 |= 1 << CS22;   //pre-scaler 256
  69.     TCCR2 |= 1 << CS21;   //pre-scaler 256
  70.     TCCR2 |= 0 << CS20;   //pre-scaler 256
  71.  
  72.     TCCR2 |= 1 << WGM20;  //fast pwm
  73.     TCCR2 |= 1 << WGM21;  //fast pwm
  74.  
  75.     TCCR2 |= 0 << COM20;  //non-inverting pwm
  76.     TCCR2 |= 1 << COM21;  //non-inverting pwm
  77.     OCR2 = 255;  //Initial value into OCR2
  78.     DDRD |= (1 << DDD7);  //setting PORTD.7 as output
  79. }
  80.  
  81. void init_pwm_left(void)
  82. {
  83.     TCCR0 |= 1 << CS02;   //pre-scaler 256
  84.     TCCR0 |= 0 << CS01;   //pre-scaler 256
  85.     TCCR0 |= 0 << CS00;   //pre-scaler 256
  86.  
  87.     TCCR0 |= 1 << WGM00;  //fast pwm
  88.     TCCR0 |= 1 << WGM01;  //fast pwm
  89.  
  90.     TCCR0 |= 0 << COM00;  //non-inverting pwm
  91.     TCCR0 |= 1 << COM01;  //non-inverting pwm
  92.     OCR0 = 255;  //Initial value into OCR0
  93.     DDRB |= (1 << DDB3);  //setting PORTB.3 as output
  94. }
  95.  
  96.  
  97.  
  98. void start_pwm_right(void)
  99. {
  100.     TCCR2 |= (1 << CS22);   //pre-scaler, 256
  101.     TCCR2 |= (1 << CS21);   //pre-scaler, 256 
  102.     TCCR2 |= (0 << CS20);   //pre-scaler, 256
  103. }
  104.  
  105.  
  106. void start_pwm_left(void)
  107. {
  108.     TCCR0 |= (1 << CS02);   //pre-scaler 256
  109.     TCCR0 |= (0 << CS01);   //pre-scaler 256
  110.     TCCR0 |= (0 << CS00);   //pre-scaler 256
  111. }
  112.  
  113.  
  114. void stop_pwm_right(void)
  115. {
  116.     TCCR2 &= ~(1 << CS22);   //NO pre-scaler, timer stopped
  117.     TCCR2 &= ~(1 << CS21);   //NO pre-scaler, timer stopped
  118.     TCCR2 &= ~(1 << CS20);   //NO pre-scaler, timer stopped
  119. }
  120.  
  121.  
  122. void stop_pwm_left(void)
  123. {
  124.     TCCR0 &= ~(1 << CS02);   //NO pre-scaler, timer stopped
  125.     TCCR0 &= ~(1 << CS01);   //NO pre-scaler, timer stopped
  126.     TCCR0 &= ~(1 << CS00);   //NO pre-scaler, timer stopped
  127. }
  128.