boostconv.c

/*
Code adapted from http://reibot.org/2011/08/07/intro-to-boost-converter/.
Tested with an Arduino Pro Mini.
*/
const int pwm_pin = 0;
const int fb_pin = 24;
const int manual = 0;

void setup(){
   DDRD |= (1<<PD6);
   TCNT0 = 0;
   TCCR0A=0;
   TCCR0B=0;
   
   TCCR0A |= (1<<COM0A1);                  // Timer0 in toggle mode Table 11-2
   TCCR0A |= (1 << WGM02) | (1 << WGM00);  // phase-correct PWM (Table 15-8)
   TCCR0B |= (1 << CS00);                  // undivised clock
   OCR0A=104;                              // Default compare value for Timer 0
}

void loop(){
  
  if (manual) { 
    double multiplier = analogRead(fb_pin) / 1023.;
    OCR0A = (255. * multiplier);
  } else {
    /*
    The setup is this:
    
    Vin ---R1---o---R2---GND
                |
              fb_pin
     
     R1/R2 is chosen so that voltage at fb_pin
     does not exceed 5V. Vin is voltage from boost conv.
     */
    double targetVoltage = 34;
    double R2 = 98.8e3;
    double R1 = 1070e3;
    double voltage = (analogRead(fb_pin)/1023.)*4.9*(R2+R1)/R2;
    
    if(voltage < targetVoltage){
      // Tune this value depending on your inductor.
      // Use manual mode to estimate the right PWM frequency
      // that yields the best results, then use it here.
      OCR0A = 100; // turn transistor mostly off
    }
    if(voltage > targetVoltage){
      OCR0A = 0;   // turn transistor always on
    }
  }
}