DIY car steering wheel controller with volume control

 /* Read Quadrature Encoder
  * Connect Encoder to Pins encoder0PinA, encoder0PinB, and +5V.
  *
  * www.setnfix.com
  * 
  *
  */  


 int val; 
 int encoder0PinA = 0; 
 int encoder0PinB = 1; 
 int test = A2;
 int testdata=0;
 int volP = A3; // Volume control +
 int volM = A1;// Volume control -
 int encoder0Pos = 0;
 int encoder0PinALast = LOW;
 int n = LOW;
// int BOOT = 3; //boot up set
// int ampoff = 11;
/// int AMP=2;
 //int POWER = 5;

 // Variables will change :
//int ledState = LOW;             // ledState used to set the LED

// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0;        // will store last time LED was updated

// constants won't change :
const long interval = 1800000;           // interval at which to blink (milliseconds)

 void setup() { 
   pinMode (encoder0PinA,INPUT);
   pinMode (encoder0PinB,INPUT);
   pinMode (test,INPUT);
   //pinMode (BOOT,OUTPUT);
   pinMode (volP,OUTPUT);
   pinMode (volM,OUTPUT);
 } 

 void loop() { 



testdata = analogRead(test);

    
   n = digitalRead(encoder0PinA);
   if ((encoder0PinALast == LOW) && (n == HIGH)) {
     if (digitalRead(encoder0PinB) == LOW) {
       VolumeUP();
       //delay(200);
     } else {
      VolumeDOWN();
      //delay(200);
     }
     //Serial.print (encoder0Pos);
    // Serial.print ("/");
   } 
   encoder0PinALast = n;
   
   
   //POWERON/OFF switch

     unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // set the LED with the ledState of the variable:
    //digitalWrite(POWER, ledState);
  }
   
   
   
   }

   void VolumeUP(){
    digitalWrite(volP,HIGH);
    delay(500);
    digitalWrite(volP,LOW);
   }

   void VolumeDOWN(){
    digitalWrite(volM,HIGH);
    delay(500);
    digitalWrite(volM,LOW);
   }