Button holding function

Projects Programming
1 
const int controlPin1 = 2; // connected to pin 7 on the H-bridge
const int controlPin2 = 3; // connected to pin 2 on the H-bridge
const int enablePin = 9;   // connected to pin 1 on the H-bridge
const int directionSwitchPin = 4;  // connected to the switch for direction
const int onOffSwitchStateSwitchPin = 5; // connected to the switch for turning the motor on and off
const int potPin = A0;  // connected to the potentiometer's output

// create some variables to hold values from your inputs
int onOffSwitchState = 0;  // current state of the on/off switch
int previousOnOffSwitchState = 0; // previous position of the on/off switch
int directionSwitchState = 0;  // current state of the direction switch
int previousDirectionSwitchState = 0;  // previous state of the direction switch

int motorEnabled = 0; // Turns the motor on/off
int motorSpeed = 0; // speed of the motor
int motorDirection = 1; // current direction of the motor

void setup() {
  // initialize the inputs and outputs
  pinMode(directionSwitchPin, INPUT);
  pinMode(onOffSwitchStateSwitchPin, INPUT);
  pinMode(controlPin1, OUTPUT);
  pinMode(controlPin2, OUTPUT);
  pinMode(enablePin, OUTPUT);

  // pull the enable pin LOW to start
  digitalWrite(enablePin, LOW);
}

void loop() {
  // read the value of the on/off switch
  onOffSwitchState = digitalRead(onOffSwitchStateSwitchPin);
  delay(1);

  // read the value of the direction switch
  directionSwitchState = digitalRead(directionSwitchPin);

  // read the value of the pot and divide by 4 to get a value that can be
  // used for PWM
  motorSpeed = analogRead(potPin) / 4;

  // if the on/off button changed state since the last loop()
  if (onOffSwitchState != previousOnOffSwitchState) {
    // change the value of motorEnabled if pressed
    if (onOffSwitchState == HIGH) {
      motorEnabled = !motorEnabled;
    }
  }

  // if the direction button changed state since the last loop()
  if (directionSwitchState != previousDirectionSwitchState) {
    // change the value of motorDirection if pressed
    if (directionSwitchState == HIGH) {
      motorDirection = !motorDirection;
    }
  }

  // change the direction the motor spins by talking to the control pins
  // on the H-Bridge
  if (motorDirection == 1) {
    digitalWrite(controlPin1, HIGH);
    digitalWrite(controlPin2, LOW);
  } else {
    digitalWrite(controlPin1, LOW);
    digitalWrite(controlPin2, HIGH);
  }

  // if the motor is supposed to be on
  if (motorEnabled == 1) {
    // PWM the enable pin to vary the speed
    analogWrite(enablePin, motorSpeed);
  } else { // if the motor is not supposed to be on
    //turn the motor off
    analogWrite(enablePin, 0);
  }
  // save the current on/off switch state as the previous
  previousDirectionSwitchState = directionSwitchState;
  // save the current switch state as the previous
  previousOnOffSwitchState = onOffSwitchState;
}

I’m currently learning Arduino from the starter kit. I’m stuck at starter kit project 10. .
What I do not understand is the button toggle function. How does pressing the button once and the motor will turn until I press the button again to stop it(toggle). I’m confuse with the “onOffSwitchState != previousOnOffSwitchState” how does it help with the toggle. Can anyone help explain in simple to understand format?

2

I'm confuse with the "onOffSwitchState != previousOnOffSwitchState" how does it help with the toggle.

You have not posted the whole program but what the snippet that you posted does is to check whether the switch state has changed (HIGH to LOW or LOW to HIGH. Either way not in its previous state) and if so whether it is now HIGH (presumably pressed). If so then motorEnabled is changed from true to false or vice versa

Look at the StateChangeDetection example in the IDE. The code is detecting when the button becomes pressed rather than when it is pressed.