Some error in coding a proximity Sensor.. Anyone can help me?

Using Arduino Programming Questions
#1

Hello everyone!! I would like to know what is my error in my code… So first, I should tell what I’m doing/ what I have… I have a Gizduino Plus 644 ( a copy of Arduino with ATmega 644 here in the Philippines…), a IR Proximity Sensor (Digital - 0 or 1), LED and some resistor.

In this code, everything is working perfectly…
If the proximity sense something, the LED will turn on.

int PROX = 12;
int SENSOR = 2;
int SENSOR_LED = 7;

void setup()
{
  pinMode(PROX, OUTPUT);
  pinMode(SENSOR, INPUT_PULLUP);
  pinMode(SENSOR_LED, OUTPUT);
}

void loop()
{
  digitalWrite(PROX, HIGH);
  digitalWrite(SENSOR_LED, LOW);
  
  int VAL = digitalRead(SENSOR);
  
  if (VAL > 0)
  {
    digitalWrite(SENSOR_LED, HIGH);
  }
}

But when I try it to this code… There’s some error… If I run the program (upload it), and type “QRIN” the LED is already ON even if the Proximity doesn’t sense anything… And if I type “QROUT”, the LED is still on… In which it should not.

int LOCK = 13;
int PROX = 12;
int SENSOR = 2;
int PROX_SENSOR_LED = 7;

void setup()
{
  Serial.begin(9600);
  pinMode(LOCK, OUTPUT);
  pinMode(PROX, OUTPUT);
  pinMode(SENSOR, INPUT_PULLUP);
  pinMode(PROX_SENSOR_LED, OUTPUT);
}

void loop()
{ 
  char data = Serial.read();
  
  switch (data)
  {
    case 'QRIN':
                digitalWrite(PROX, HIGH);
                digitalWrite(LOCK, HIGH);
                digitalWrite(PROX_SENSOR_LED, HIGH);
                SENSOR_LED();
                break;
    case 'QROUT':
                digitalWrite(PROX, LOW);
                LED_OFF();
                digitalWrite(LOCK, HIGH);
                delay(10000);
                digitalWrite(LOCK, LOW);
                break;
  }
}

void SENSOR_LED()
{
  int VAL = digitalRead(SENSOR);
  if (VAL > 0)
  {
    digitalWrite(PROX_SENSOR_LED, HIGH);
  }
}

void LED_OFF()
{
  int VAL = digitalRead(SENSOR);
  if (VAL > 0)
  {
    digitalWrite(PROX_SENSOR_LED, LOW);
  }
}

I’m doing this because I need this for a project… I have a c# program that if the QR that my Webcam reads is correct, the “QRIN” will execute and if the other Webcam reads the QR is correct, it will execute “QROUT”… ← this is already working… The only problem is my code in Arduino IDE…

I’m really sorry for the long post… Please bear with me… I’m really new to Arduino…

#2

Single quote marks define only a single byte. Therefore it can not contain you sequence. A Serial.read reads only a single byte therefore it can not hold your sequence of key presses.

You should put your serial input into a char array and compare then with an if statement.

#3

You should put your serial input into a char array and compare then with an if statement.

The if statement needs to contain a call to strcmp(), too.

Serial Input Basics - updated is a good place to start.

#4