//Declare port where read potentiometer value
#define inpot A0
char key; //Declare variable to store key
int period; //T o periodo dell'onda QUADRATA
float perc_dc; //Percentuale duty cycle
void dc(); //Declare DC generator as void

void setup(){
    Serial.begin(9600);
    pinMode(AO, INPUT);
    DDRD= DDRD | B00111100; //Pin 2-5 OUTPUT
    period= 100;
}

void loop(){
    key= Serial.Read(); //Reading keyboard char on Serial
    perc_dc= AnalogRead(AO)/1023 //Convertion potentiometer in duty cycle
    if (key=='c') PORTD= B00111100; //PINs 2-5 ON
    else if (key=='a') dc(); //Use DC generator
    else PORTD= B00000000; //All PINs OFF
}

void dc(){
    PORTD= B00111100; //Set all led ON
    delaymicroseconds(period/perc_dc); //Waiting first part of wave
    PORTD= B00000000; //Set all led OF
    delaymicroseconds(period/(1-perc_dc)); //Waiting second part of ware
}