Seven-segment display control in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output on the seven-segment display?

Consider this Arduino code snippet controlling a common cathode seven-segment display connected to pins 2 to 8. What digit will be shown on the display?

Arduino

const int segmentPins[] = {2, 3, 4, 5, 6, 7, 8};
// Segments a,b,c,d,e,f,g
const byte digit2Segments = 0b01011011; // segments to light for digit '2'

void setup() {
  for (int i = 0; i < 7; i++) {
    pinMode(segmentPins[i], OUTPUT);
  }
  for (int i = 0; i < 7; i++) {
    bool segmentOn = digit2Segments & (1 << i);
    digitalWrite(segmentPins[i], segmentOn ? HIGH : LOW);
  }
}

void loop() {
  // nothing here
}

A Digit '3' is displayed

B No segments light up

C Digit '5' is displayed

D Digit '2' is displayed

💡 Hint

Look at the binary pattern and which segments correspond to each bit.

The binary pattern 0b01011011 corresponds to segments a, b, d, e, and g lit, which forms the digit '2' on a common cathode display.

🧠 Conceptual

intermediate

Which pin controls the 'g' segment in this setup?

Given the array const int segmentPins[] = {2, 3, 4, 5, 6, 7, 8}; representing segments a to g respectively, which pin controls the 'g' segment?

A Pin 5

B Pin 8

C Pin 7

D Pin 2

💡 Hint

Remember the order is a, b, c, d, e, f, g in the array.

The array index 6 corresponds to segment 'g'. Since arrays start at 0, segment 'g' is at segmentPins[6], which is pin 8.

🔧 Debug

advanced

Why does the display show nothing?

This Arduino code is supposed to display digit '1' on a common cathode seven-segment display, but the display stays off. What is the cause?

Arduino

const int segmentPins[] = {2, 3, 4, 5, 6, 7, 8};
const byte digit1Segments = 0b00000110; // segments b and c

void setup() {
  for (int i = 0; i < 7; i++) {
    pinMode(segmentPins[i], OUTPUT);
  }
  for (int i = 0; i < 7; i++) {
    bool segmentOn = digit1Segments & (1 << i);
    digitalWrite(segmentPins[i], segmentOn ? HIGH : LOW);
  }
}

void loop() {
  // nothing
}

A Pins are set LOW to turn on segments, but it's a common cathode display needing HIGH

B Pins are set HIGH to turn on segments, but it's a common anode display needing LOW

C Pin modes are not set to OUTPUT

D The bitmask for digit '1' is incorrect

💡 Hint

Check how HIGH and LOW relate to turning on segments for common cathode vs anode.

For a common cathode display, segments turn on when the pin is set HIGH. The code sets pins LOW to turn on segments, so no segments light up.

📝 Syntax

advanced

Which option fixes the syntax error in this seven-segment control code?

Identify the option that fixes the syntax error in this Arduino code snippet:

for (int i = 0; i < 7; i++)
  digitalWrite(segmentPins[i], digitSegments & (1 << i) ? HIGH : LOW

A Remove the ternary operator and write digitalWrite(segmentPins[i], HIGH);

B Replace digitalWrite with digitalRead

C Add a closing parenthesis at the end: digitalWrite(segmentPins[i], digitSegments & (1 << i) ? HIGH : LOW);

D Add a semicolon after the for loop header

💡 Hint

Look carefully at parentheses and semicolons.

The original code misses a closing parenthesis for digitalWrite's arguments, causing a syntax error.

🚀 Application

expert

How many segments light up for digit '8' on a common cathode display?

Given the standard seven-segment display segments labeled a to g, how many segments must be lit to display the digit '8'?

A 7 segments

B 5 segments

C 6 segments

D 4 segments

💡 Hint

Digit '8' lights all segments on a seven-segment display.

The digit '8' lights all seven segments (a, b, c, d, e, f, g) on the display.