Turn on LED while the button is pressed

Homework 4.5   Turn on LED while the button is pressed

 

    const int LED = 13;  // Arduino digital pin 13 is the pin for the LED

    const int BUTTON = 7;  // Arduino digital pin 13 the input pin where the push-button is connected

    int val = 0;  // val will be used to store the state of the input pin

    int old_val = 0;  // this variable stores the previous // value of "val"

    int state = 0;  // 0 = LED off and 1 = LED on

void setup() 

{

     pinMode(LED, OUTPUT);  // tell Arduino LED is an output

     pinMode(BUTTON, INPUT);  // tell Arduino BUTTON is an input

}

void loop()

{

    val = digitalRead(BUTTON);  // read input value and store it

    if ((val == HIGH) && (old_val == LOW)){

     state = 1 - state;

     delay(10);

}

    old_val = val; 

if (state == 1) 

{

     digitalWrite(LED, HIGH); 

} 

else 

{

     digitalWrite(LED, LOW);

}

}

////////////////////////////////////////////////////////

//Explain

val = 0

old-val = 0

state = 0

// HIGH = 1,LOW = 0

+When a push button is pressed

val = 1

old-val = 0

state = 0

if((val == HIGH)&&(old-val==LOW)) //true

state = 1-0 = 1

old-val = val = 1

if(state == 1) //true

(LED,HIGH) = Bright

+When a push button is released

val = 0

old-val = 1

state = 1

if((val == HIGH)&&(old-val==LOW)) //false : no action

old-val = val = 0

if(state == 1) //true

(LED,HIGH) = Bright

+When a push button is pressed again

val = 1

old-val = 0

state = 1

if((val == HIGH)&&(old-val==LOW)) //true

state = 1-1 = 0

old-val = val = 1

if(state == 1) //false no : action

(LED,LOW) = Dark

+When a push button is released

val = 0

old-val = 1

state = 0

if((val == HIGH)&&(old-val==LOW)) //false :​​ no action

old-val = val = 0

if(state == 1) //false no : action

(LED,LOW) = Dark

+Picture

​