Day 52 – Night Session: IoT – Arduino Programming: Digital Read/Write – ECET 2026

In ECET 2026 IoT section, Arduino programming is one of the most scoring topics. Questions often come from digital read and write functions, pin configurations, and basic code snippets.

📘 Concept Notes

🔌 What is Arduino?

• Arduino is an open-source microcontroller platform used in IoT projects.
• Provides digital pins (HIGH/LOW signals) and analog pins for sensors.
• Programs are written in Arduino IDE (C/C++ based).

⚙️ Digital Write in Arduino

• Used to send HIGH or LOW signal to a pin.
• Syntax:

digitalWrite(pin, value);

digitalWrite(pin, value);

Where:

• pin = pin number (e.g., 13).
• value = HIGH (5V) or LOW (0V).

👉 Example: LED ON/OFF

int led = 13;
void setup() {
  pinMode(led, OUTPUT);
}
void loop() {
  digitalWrite(led, HIGH); // LED ON
  delay(1000);
  digitalWrite(led, LOW);  // LED OFF
  delay(1000);
}

int led = 13;
void setup() {
  pinMode(led, OUTPUT);
}
void loop() {
  digitalWrite(led, HIGH); // LED ON
  delay(1000);
  digitalWrite(led, LOW);  // LED OFF
  delay(1000);
}

⚡ Digital Read in Arduino

• Used to read signal (HIGH/LOW) from input devices like switches, sensors.
• Syntax:

digitalRead(pin);

digitalRead(pin);

👉 Example: Button-controlled LED

int led = 13;
int button = 2;
int state = 0;

void setup() {
  pinMode(led, OUTPUT);
  pinMode(button, INPUT);
}
void loop() {
  state = digitalRead(button);
  if(state == HIGH) {
    digitalWrite(led, HIGH);
  } else {
    digitalWrite(led, LOW);
  }
}

int led = 13;
int button = 2;
int state = 0;

void setup() {
  pinMode(led, OUTPUT);
  pinMode(button, INPUT);
}
void loop() {
  state = digitalRead(button);
  if(state == HIGH) {
    digitalWrite(led, HIGH);
  } else {
    digitalWrite(led, LOW);
  }
}

🔋 Formula – Digital Logic Levels

• Logic HIGH = (for Arduino Uno)
• Logic LOW =

🛠 Applications of Digital Read/Write in IoT

• LED ON/OFF control.
• Button press detection.
• Motion detection using IR sensors.
• Home automation switches.
• Smart IoT devices (light, fan control).

🔟 10 Expected MCQs – ECET 2026

Q1. In Arduino, digitalWrite(pin, HIGH) means:
A) Send 0V to pin
B) Send 5V to pin
C) Read from pin
D) Reset pin

Q2. Default logic HIGH voltage in Arduino Uno is:
A) 0V
B) 3.3V
C) 5V
D) 12V

Q3. Which function is used to read digital input?
A) digitalWrite()
B) digitalRead()
C) analogRead()
D) pinMode()

Q4. Pin configured as INPUT is set using:
A) digitalRead()
B) pinMode(pin, INPUT)
C) digitalWrite()
D) None

Q5. If LED is connected to pin 13 and HIGH signal is written, LED will:
A) Blink
B) Stay ON
C) Stay OFF
D) Burn

Q6. digitalRead() returns:
A) Boolean (true/false)
B) Analog value (0–1023)
C) Either HIGH or LOW
D) None

Q7. A push button press corresponds to:
A) HIGH (5V)
B) LOW (0V)
C) Depends on circuit
D) Both A & B possible

Q8. Arduino code pinMode(5, OUTPUT); means:
A) Pin 5 used for input
B) Pin 5 used for output
C) Pin 5 disabled
D) Pin 5 analog input

Q9. For logic HIGH in Arduino Uno, voltage is:
A)
B)
C)
D)

Q10. Which is NOT an application of digital read/write?
A) LED control
B) Sensor interfacing
C) Data storage in EEPROM
D) Button press detection

✅ Answer Key

🧠 Explanations

• Q1 → B: HIGH = 5V output.
• Q2 → C: Arduino Uno works at 5V logic.
• Q3 → B: digitalRead() used for digital input.
• Q4 → B: pinMode sets pin as INPUT.
• Q5 → B: HIGH keeps LED ON.
• Q6 → C: digitalRead() returns HIGH or LOW.
• Q7 → C: Push button output depends on wiring.
• Q8 → B: pinMode(5, OUTPUT) → pin 5 as output.
• Q9 → C: Logic HIGH in Uno = 5V.
• Q10 → C: EEPROM storage is separate, not digital I/O.

🎯 Why Practice Matters

• Arduino questions are direct and code-based.
• Practicing syntax and examples ensures quick scoring.
• IoT section in ECET is a sure-shot scoring area if basics are clear.

📲 Join Our ECET Prep Community on WhatsApp

👉 Join WhatsApp Group – Click Here