Question

I have a program for Arduino written such that when I hold a button down, it will turn an LED off. I want to be able to print to the serial monitor how long the button was pressed for after I let go of the button. Does anybody have any ideas? Below is the code I have written thus far:

/I constants won't change. They're used here to // set pin numbers: define LED RED LED define buttonPIN PUSH2 const int buttonPin = PUSH2; const int ledPin GREEN LED; // the number of the pushbutton pin // the number of the LED pin /I variables will change: int buttonstate = 0; // variable for reading the pushbutton status void setup) // initialize the LED pin as an output: pinMode (ledPin, OUTPUT) // initialize the pushbutton pin as an input: pinMode (buttonPin, INPUT_PULLUP) void loop ) // read the state of the pushbutton value: buttonState digita!Read (buttonPin) ; // check if the pushbutton is pressed // if it is, the buttonState is HIGH: if (buttonStateHIGH) I turn LED on: digitalWrite (ledPin, HIGH) else /I turn LED off: digitalWrite (ledPin, LOW)

Text of Code:

#define LED RED_LED
#define buttonPIN PUSH2

const int buttonPin = PUSH2; // the number of the pushbutton pin
const int ledPin = GREEN_LED; // the number of the LED pin

// variables will change:
int buttonState = 0; // variable for reading the pushbutton status

void setup() {
// initialize the LED pin as an output:
pinMode(ledPin, OUTPUT);   
// initialize the pushbutton pin as an input:
pinMode(buttonPin, INPUT_PULLUP);
}

void loop(){
// read the state of the pushbutton value:
buttonState = digitalRead(buttonPin);

// check if the pushbutton is pressed.
// if it is, the buttonState is HIGH:
if (buttonState == HIGH) {
// turn LED on:   
digitalWrite(ledPin, HIGH);  
}
else {
// turn LED off:
digitalWrite(ledPin, LOW);
}
}

Answer 1

One way to work around this is using millis() function. When called at a point in the program, this counts elapsed miliseconds since the arduino begins the execution of the current program. (Please refer to the arduino reference on the same function)

To count the total time of holding the button in pushed state, it should be the difference of the timestamps of:

When buttonState == HIGH resulted TRUE and the led state was turned to HIGH by digitalWrite(ledPin, HIGH) upto when the led state was turned to low by digitalWrite(ledPin, LOW)

i.e. we need to place the timers at the following places in the codes:

1) First Timestamp

if (buttonState == HIGH) {
check_time_1=millis();
digitalWrite(ledPin, HIGH);

}

2) Second Timestamp

else {
digitalWrite(ledPin, LOW);
check_time_2=millis(); }

We can now take the different between check_time_2 and check_time_1 to output the desired time spent in holding the button.

NOTE: There are issues with the overflow of the timer count in millis() if the program execution goes beyond certain limit. But, in the given case, it is highly unlikely as holding a button, at maximum, will span few minutes. Though, if required, overflow can also be worked around. Please explore on the techinques for properly measuring time intervals with overflow possibilities in arduino, if required.

Hope it helps! If it works please thumbs up!