Program Structure: declare ButtonState: Global variable holding status of button unsigned long
Button Time: Holds time to debounce Switch int Button NextState( input) function that is to be
called in loop to service the switch switch based on ButtonState Idle: State where nothing has
been happening. if input is low, Button Time millis0: Record time of high to low transition. set
ButtonState to Wait Move to Wait state. Wait: Button has gone low and we are waiting for it to
remain low for 5 milliseconds if input is high. l f button has gone high. set ButtonState to Idle
Reset back to Idle else if (millis0- Button Time 5 if 5 milliseconds has passed. set ButtonState to
Low Move to low state. return 1 indicating that button has been pressed Low Button is low and
has been so for 5 milliseconds. if input is high Once button released. set ButtonState to Idle: end
of switch return 0 By default return 0 indicating nothing is happening. setup: Function run at the
start of the program. Set pin as input Check Schematic in Lab 4 for pin number. Set ButtonState
to Idle Initialize state loop Function continuously called Check status of button. if
ButtonNextState( digitalRead( input)) Send serial message indicating button press Indicate
button has been pressed end of if
Solution
//initialize and declare variables
const int ledPin = 13; //led attached to this pin
const int buttonPin = 2; //push button attached to this pin
int buttonState = LOW; //this variable tracks the state of the button, low if not pressed, high if
pressed
int ledState = -1; //this variable tracks the state of the LED, negative if off, positive if on
long lastDebounceTime = 0; // the last time the output pin was toggled
long debounceDelay = 50; // the debounce time; increase if the output flickers
void setup() {
//set the mode of the pins...
pinMode(ledPin, OUTPUT);
pinMode(buttonPin, INPUT);
}//close void setup
void loop() {
//sample the state of the button - is it pressed or not?
buttonState = digitalRead(buttonPin);
//filter out any noise by setting a time buffer
if ( (millis() - lastDebounceTime) > debounceDelay) {
//if the button has been pressed, lets toggle the LED from \"off to on\" or \"on to off\"
if ( (buttonState == HIGH) && (ledState < 0) ) {
digitalWrite(ledPin, HIGH); //turn LED on
ledState = -ledState; //now the LED is on, we need to change the state
lastDebounceTime = millis(); //set the current time
}
else if ( (buttonState == HIGH) && (ledState > 0) ) {
digitalWrite(ledPin, LOW); //turn LED off
ledState = -ledState; //now the LED is off, we need to change the state
lastDebounceTime = millis(); //set the current time
}//close if/else
}//close if(time buffer)
}//close void loop.
Program Structure declare ButtonState Global variable holding statu.pdf
1. Program Structure: declare ButtonState: Global variable holding status of button unsigned long
Button Time: Holds time to debounce Switch int Button NextState( input) function that is to be
called in loop to service the switch switch based on ButtonState Idle: State where nothing has
been happening. if input is low, Button Time millis0: Record time of high to low transition. set
ButtonState to Wait Move to Wait state. Wait: Button has gone low and we are waiting for it to
remain low for 5 milliseconds if input is high. l f button has gone high. set ButtonState to Idle
Reset back to Idle else if (millis0- Button Time 5 if 5 milliseconds has passed. set ButtonState to
Low Move to low state. return 1 indicating that button has been pressed Low Button is low and
has been so for 5 milliseconds. if input is high Once button released. set ButtonState to Idle: end
of switch return 0 By default return 0 indicating nothing is happening. setup: Function run at the
start of the program. Set pin as input Check Schematic in Lab 4 for pin number. Set ButtonState
to Idle Initialize state loop Function continuously called Check status of button. if
ButtonNextState( digitalRead( input)) Send serial message indicating button press Indicate
button has been pressed end of if
Solution
//initialize and declare variables
const int ledPin = 13; //led attached to this pin
const int buttonPin = 2; //push button attached to this pin
int buttonState = LOW; //this variable tracks the state of the button, low if not pressed, high if
pressed
int ledState = -1; //this variable tracks the state of the LED, negative if off, positive if on
long lastDebounceTime = 0; // the last time the output pin was toggled
long debounceDelay = 50; // the debounce time; increase if the output flickers
void setup() {
//set the mode of the pins...
pinMode(ledPin, OUTPUT);
pinMode(buttonPin, INPUT);
}//close void setup
void loop() {
//sample the state of the button - is it pressed or not?
buttonState = digitalRead(buttonPin);
//filter out any noise by setting a time buffer
if ( (millis() - lastDebounceTime) > debounceDelay) {
//if the button has been pressed, lets toggle the LED from "off to on" or "on to off"
2. if ( (buttonState == HIGH) && (ledState < 0) ) {
digitalWrite(ledPin, HIGH); //turn LED on
ledState = -ledState; //now the LED is on, we need to change the state
lastDebounceTime = millis(); //set the current time
}
else if ( (buttonState == HIGH) && (ledState > 0) ) {
digitalWrite(ledPin, LOW); //turn LED off
ledState = -ledState; //now the LED is off, we need to change the state
lastDebounceTime = millis(); //set the current time
}//close if/else
}//close if(time buffer)
}//close void loop
