#define output(directions,pin) (directions |= pin) // set port direction for output
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin
#define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
#define position_delay() _delay_ms(1000)

#define PWM_port PORTB
#define PWM_direction DDRB
#define PWM_pin_0 (1 << PB0)

#define loop_count 40

uint8_t i;

void setup() {
   //
   // set clock divider to /1
   //
   CLKPR = (1 << CLKPCE);
   CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
   //
   // set PWM pins to output
   //
   clear(PWM_port, PWM_pin_0);
   output(PWM_direction, PWM_pin_0);

}

void loop() {
      //
      // 1 ms on time, -90°
      //
      for (i = 0; i < loop_count; ++i) {
         set(PWM_port,PWM_pin_0);
         _delay_us(650);
         clear(PWM_port,PWM_pin_0);
         _delay_us(19250);
         }
      //
      // 1.5 ms on time, 0°
      //
      for (i = 0; i < loop_count; ++i) {
         set(PWM_port,PWM_pin_0);
         _delay_us(1400);
         clear(PWM_port,PWM_pin_0);
         _delay_us(18600);
         }
      //
      // 2 ms on time, +90°
      //
      for (i = 0; i < loop_count; ++i) {
         set(PWM_port,PWM_pin_0);
         _delay_us(2550);
         clear(PWM_port,PWM_pin_0);
         _delay_us(17450);
         }
      //
      // 1.5 ms on time, 0°
      //
      for (i = 0; i < loop_count; ++i) {
         set(PWM_port,PWM_pin_0);
         _delay_us(1450);
         clear(PWM_port,PWM_pin_0);
         _delay_us(18550);
         }

}