Arduino Example using two simple user-defined functions

The sketch below is used to alternately flash a pair of green and red LEDs whenever a potentiometer is turned pass a threshold position. The "trick" to this type of action is to only call the flash lights function once. The idea here is to flash the lights once - in order to flash them again, the user needs to "reset" the system by turning the potentiometer down pass a second lower threshold value and then again turning it up pas the upper threshold setting.

There a many different ways to accomplish this. The method shown below sets a "flag" whenever the pot value goes high. The flag is then reset when the pot goes low.

The flash lights() function is only called when the potValue goes above the threshold and the flag is set. Once the lights() function is called the flag is changed and needs to be reset before the function can be called again.

Here is a video of the circuit and the sketch is below...

VIDEO


SKETCH

	/* Shows the use of a user-defined function call from loop().
	The sketch also uses a flag variable to keep track of the
	current position state of the potentiometer.
	The potentiometer is used to provide and analog signal to pin
	A0. When the value of the analog read variable potVal goes
	from a value that is below 400 to a value that is above
	the threshold value of 600 the function lights() is called to
	flash the green and red LEDs. The function is not called again
	until the pot is again cycle below 400 and then above 600. This
	check is made using the variable flag.
	The initial state of the potentiometer and thus the flag value is
	determine in the setup() by calling the user-defined function
	potState() which returns the boolean value of the flag. */
	// LED pins
	const int ledGreen = 2;
	const int ledRed = 3;
	// Potentiometer
	const int potPin = A0;
	int potVal = 0;
	// Variable to hold state of potentiometer
	boolean flag = 0;
	void setup(){
	// Set led pins as outputs
	pinMode(ledGreen, OUTPUT);
	pinMode(ledRed, OUTPUT);
	// Turn leds off
	digitalWrite(ledGreen, LOW);
	digitalWrite(ledRed, LOW);
	// Initialize serial communication for debugging
	Serial.begin(9600);
	// Call user defined function potState() to
	// read initial state of potentiometer and set flag
	flag = potState();
	}
	void loop(){
	// Read value of potentiometer
	potVal = analogRead(potPin);
	// Check if potentiometer has correct value and that
	// the flag has changed state, if TRUE, call user-
	// defined function lights().
	if (potVal > 600 && flag == 0){
	lights();
	flag = 1;
	}
	// Flag gets reset to FALSE (0) when the potentiometer
	// is turned low.
	// The 50 units between 500 and 550 provides a buffer
	// that prevents unintended resets of flag.
	if (potVal < 500){
	flag = 0;
	}
	}
	// user-defined function to check the state of the potentiometer
	boolean potState(){
	boolean check = 0;
	potVal = analogRead(potPin);
	if (potVal > 512){
	check = 1;
	}
	else{
	check = 0;
	}
	return check;
	}
	// user-defined function to flash the LED's
	void lights(){
	for (int i = 0; i < 10; i++){
	digitalWrite(ledGreen, HIGH);
	delay(50);
	digitalWrite(ledGreen, LOW);
	delay(50);
	digitalWrite(ledRed, HIGH);
	delay(50);
	digitalWrite(ledRed, LOW);
	delay(50);
	}
	}

view raw functions2 hosted with ❤ by GitHub