Arduino Sketch for DTMF Password Recognition

#include <Password.h>

/* Ths sketch will monitor 5 pin
  conected to a MT8870DE DTMF decoder
  chip and send the key pressed to the
  computer by serial comunication.
  In addition, a certain combinaison
  of number will trigger a "unlock"
  or "boot" signal. The pwd in this case will
  be "8413".

*/

int Q1 = 2; /*Q1 bit*/
int Q2 = 3; /*Q2 bit*/
int Q3 = 4; /*Q3 bit*/
int Q4 = 5; /*Q4 bit*/
int StD = 6; /*Delayed Steering; will read high when tone is pressed*/
int keypressed ;
char result ; /*the number presser stored as a character
int pwdlvl = 0 ; /*Number of appended digits*/
Password password = Password( "8413" );

void setup() {

 Serial.begin(9600); /* Open serial com*/
 /*Pins settings*/
 pinMode(Q1, INPUT);
 pinMode(Q2, INPUT);
 pinMode(Q3, INPUT);
 pinMode(Q4, INPUT);
 pinMode(StD, INPUT);

}

void loop() {

 int toneHeard = digitalRead(StD);
 if (toneHeard == HIGH) {
   delay(250);
   keypressed = interpret() ; /* Go to the interpret function to get the keypressed*/
   Serial.write(keypressed);
   password.append(keypressed);
   pwdlvl++;
   if (pwdlvl == 4){
     Serial.println();
     Serial.print("Guessing password... "); /*debuging purposes*/
     delay(500); /*debuging purposes*/
     if (password.evaluate()){ /*evaluate password*/
         Serial.println("Valid Password");
         Serial.print("Sending 5V signal for 3...");
         delay(1000);
         Serial.print("2...");
         delay(1000);
         Serial.print("1...");
         delay(1000);
         Serial.println("0...");
         password.reset(); /*Reset appended password*/
         pwdlvl = 0; /*Reset the number of appended digits to 0*/
         }
       else {
         Serial.println("Invalid Password");
          password.reset(); /*Reset appended password*/
          pwdlvl = 0; /*Reset the number of appended digits to 0*/
          }
   }
 }
 delay(1);
}

int interpret() {

  int Q1State = digitalRead(Q1);
  int Q2State = digitalRead(Q2);
  int Q3State = digitalRead(Q3);
  int Q4State = digitalRead(Q4);

  if (Q1State == HIGH && Q2State == LOW && Q3State == LOW && Q4State == LOW){result = '1' ;}
  if (Q1State == LOW && Q2State == HIGH && Q3State == LOW && Q4State == LOW){result = '2' ;}
  if (Q1State == HIGH && Q2State == HIGH && Q3State == LOW && Q4State == LOW){result = '3' ;}
  if (Q1State == LOW && Q2State == LOW && Q3State == HIGH && Q4State == LOW){result = '4' ;}
  if (Q1State == HIGH && Q2State == LOW && Q3State == HIGH && Q4State == LOW){result = '5' ;}
  if (Q1State == LOW && Q2State == HIGH && Q3State == HIGH && Q4State == LOW){result = '6' ;}
  if (Q1State == HIGH && Q2State == HIGH && Q3State == HIGH && Q4State == LOW){result = '7' ;}
  if (Q1State == LOW && Q2State == LOW && Q3State == LOW && Q4State == HIGH){result = '8' ;}
  if (Q1State == HIGH && Q2State == LOW && Q3State == LOW && Q4State == HIGH){result = '9' ;}
  if (Q1State == LOW && Q2State == HIGH && Q3State == LOW && Q4State == HIGH){result = '0' ;}

  return result;
}