Assignment 01: LED Counter

Assignment Details

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This assignment’s objectives / guidelines were, ++for the circuit++:

1. Connect two LEDs to your Arduino using a breadboard
2. Connect one switch to your Arduino using a breadboard

And ++for the code++:

1. Read a momentary switch being pressed
2. When the program starts, both LEDs are off
3. When the switch is pressed once, the first LED turns on
4. When the switch is pressed the second time, the second LED turns on (the first one should also still be on)
5. When the switch is pressed the third time, both LEDs turn off
6. Repeat this same cycle of LEDs turning on and off in sequence (off, one LED, two LEDs, off…)

My process

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The first thing I wanted to figure out was what kind of signal was read by pressing the button switch.

const int buttonPin = 6;

void setup() {
Serial.begin(4800);
pinMode(buttonPin, INPUT);
}

void loop() {
int button digitalRead(buttonPin);
Serial.println(button);
}

This helped me realize the button signal ranged from 0 to 1:

• 1 meant the button was pressed
• 0 meant the button was released

By understanding this logic I now knew I needed a way to detect a change in the signal. I needed three “states” for the LED’s:

1. LED 1 is ++OFF++, LED 2 is ++OFF++
2. LED 1 is ++ON++, LED 2 is ++OFF++
3. LED 1 is ++ON++, LED 2 is ++ON++

For this to work I decided to create a simple if/else logic that increments a variable “count” every time the signal sent by the button changes from 0 to 1 (pressed). This variable increments until it reaches 3, resetting every time that value is reached.

This code is made to detect a click, not a button press/button release. For that reason I am tracking the button’s previous state using bPrevState and its current state using pCurrentState. As an additional helper, I also created buttonWasPressed as a way to track if the button is currently being pressed.

My main challenge

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As a way to exercise good coding practices, I have the habit of printing information to the console every few lines of code when I am still building it. Because of this I realized the Serial.println() commands I added in setup() weren’t being printed. This confused me, and it’s where I spent the longest amount of time in for this Assignment. I ended up understanding that the Serial Port simply took a few ms longer to boot up than the information took to be sent out, and the issue was solved through the addition of a simple delay(2000).

Assignment Results

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This is the final code I produced for this assigment:

const int buttonPin = 6;
const int redLEDPin = 14;
const int orangeLEDPin = 15;

//for tracking the button state changes
bool bPrevState = HIGH;  //HIGH = not pressed
bool buttonWasPressed = false;

bool serialStarted = false;  //added due to delay(2000) in setup

int count = 0;  //count for states 1, 2 and 3. initialized at 0

void setup() {
  Serial.begin(4800);
  delay(2000);  //needed! serial monitor takes a bit to open, 2000 delay seems to work to print everything correctly.
  serialStarted = true;

  pinMode(buttonPin, INPUT);
  pinMode(redLEDPin, OUTPUT);
  pinMode(orangeLEDPin, OUTPUT);

  Serial.print("initial count value: ");
  Serial.println(count);
}

void loop() {
  if (serialStarted) {
    delay(10);
    bool pCurrentState = digitalRead(buttonPin);

    //detecting the press
    if (bPrevState == LOW && pCurrentState == HIGH) {
      buttonWasPressed = true;
    }

    //detecting release
    if (bPrevState == HIGH && pCurrentState == LOW) {
      if (buttonWasPressed) {
        count += 1;                //increment count
        buttonWasPressed = false;  //reset for next click

        Serial.print("count = ");
        Serial.println(count);

        //the LED on/off logic
        if (count == 1) {
          digitalWrite(redLEDPin, HIGH);
          digitalWrite(orangeLEDPin, LOW);
        } else if (count == 2) {
          digitalWrite(redLEDPin, HIGH);
          digitalWrite(orangeLEDPin, HIGH);
        } else if (count == 0 || count == 3) {
          digitalWrite(redLEDPin, LOW);
          digitalWrite(orangeLEDPin, LOW);
          count = 0;
        }
      }
    }

    bPrevState = pCurrentState;
  }
}

And these are some pictures I took of the circuit working. Respectively:

• Only the first LED on
• Both LEDs on
• Both LEDs off