Hi, i'm new to programming, I want to use a PIR sensor to switch an LED output with the function of an override using bluetooth module (from android app). The bluetooth controller will manually bypass the PIR if I want to switch it on. Appreciate any help with this 
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int a = 12;
int b = 11;
int c = 10;
int d = 9;
int pirPin = 13;
int pirState = LOW;
int val = 0;
String readString;
void setup() {
 Serial.begin(9600);
 pinMode(a, OUTPUT);
 pinMode(b, OUTPUT);
 pinMode(c, OUTPUT);
 pinMode(d, OUTPUT);
 pinMode(pirPin, INPUT);
}
void loop() {
val = digitalRead(pirPin);
if (val == HIGH){
digitalWrite(a, HIGH);
if (pirState == LOW){
 Serial.println("Motion detected!");
 pirState = HIGH;
}
}else {
 digitalWrite(a, LOW);
 if(pirState == HIGH){
  Serial.println("Motion ended!");
  pirState = LOW;
 }
}
while (Serial.available()) {
delay(3);
char c = Serial.read();
readString += c;
}
if (readString.length() >0) {
Serial.println(readString);
if (readString == "on1")
{
digitalWrite(a, HIGH);
}
if (readString == "off1")
{
digitalWrite(a, LOW);
}
if (readString == "on2")
{
digitalWrite(b, HIGH);
}
if (readString == "off2")
{
digitalWrite(b, LOW);
}
if (readString == "on3")
{
digitalWrite(c, HIGH);
}
if (readString == "off3")
{
digitalWrite(c, LOW);
}
if (readString == "on4")
{
digitalWrite(d, HIGH);
}
if (readString == "off4")
{
digitalWrite(d, LOW);
}
if (readString == "af")
{
digitalWrite(a, LOW);
digitalWrite(b, LOW);
digitalWrite(c, LOW);
digitalWrite(d, LOW);
}
readString="";
}
}