FREE SIMULATOR EXAMPLE · BEGINNER

ESP32: 7-Segment Counter

This example counts 0 to 9 on a single 7-segment display, stepping every 700 ms, with seven GPIOs driving the seven segments directly — a=12, b=13, c=14, d=25, e=26, f=27, g=32. No driver chip, no library: just a lookup table and digitalWrite. The Serial Monitor prints each digit as it lights.

Board	ESP32 DevKit (Xtensa LX6, 240 MHz)
Difficulty	beginner
Category	displays
Libraries	None — just the Arduino core
Runs in	Sensbench browser simulator — free, no account

The exact circuit you get when you open this example — already wired, ready to run.

The sketch

// ESP32 — 7-Segment Display Counter 0-9
// Segments: a=12, b=13, c=14, d=25, e=26, f=27, g=32


const int SEG[7] = {12, 13, 14, 25, 26, 27, 32};

const bool DIGITS[10][7] = {
  {1,1,1,1,1,1,0}, // 0
  {0,1,1,0,0,0,0}, // 1
  {1,1,0,1,1,0,1}, // 2
  {1,1,1,1,0,0,1}, // 3
  {0,1,1,0,0,1,1}, // 4
  {1,0,1,1,0,1,1}, // 5
  {1,0,1,1,1,1,1}, // 6
  {1,1,1,0,0,0,0}, // 7
  {1,1,1,1,1,1,1}, // 8
  {1,1,1,1,0,1,1}, // 9
};


void showDigit(int d) {
  for (int i = 0; i < 7; i++)
    digitalWrite(SEG[i], DIGITS[d][i] ? HIGH : LOW);
}

void setup() {
  for (int i = 0; i < 7; i++) pinMode(SEG[i], OUTPUT);
  Serial.begin(115200);
  Serial.println("ESP32 7-Segment Counter");
}

void loop() {
  for (int d = 0; d <= 9; d++) {
    showDigit(d);
    Serial.print("Digit: "); Serial.println(d);
    delay(700);
  }
}

How it works

The whole driver is a truth table. DIGITS[10][7] holds one row per digit and one column per segment — 1 means lit — and showDigit() walks the SEG[] pin array writing each bit with digitalWrite(). Want a custom character, like the letter E? Add the row; the code does not care whether the pattern is a digit.

The pin choices are deliberate. Every pin in SEG[] — 12, 13, 14, 25, 26, 27, 32 — is a fully output-capable GPIO on the ESP32, and they are ordered so the wiring on the canvas runs neatly around the display. The sketch spends seven pins to avoid needing any external hardware at all.

Timing is a plain blocking delay(700) inside a for loop in loop(). Crude, but honest: with nothing else to do, blocking code is the simplest correct option, and the Serial.print() pair mirrors each digit so you can verify the table against what you see lit.

Before you build it for real

Get the parts

Related examples

FAQ

Is this a common-cathode or common-anode display?

Common cathode: the shared pin goes to GND and writing a segment HIGH lights it, which matches the 1s in the DIGITS table. If your real module is common anode, the logic inverts — write !DIGITS[d][i] in showDigit() and tie the common pin to 3V3.

How do I drive a multi-digit display?

By multiplexing: all digits share the same seven segment lines, and you switch each digit’s common pin on one at a time, fast enough that persistence of vision merges them into a steady readout. You need one extra GPIO per digit and a timer instead of delay(). It is the standard next step after this example.