FREE SIMULATOR EXAMPLE · BEGINNER

STM32: 7-Segment Counter

This example counts from 0 to 9 on a 7-segment display driven by seven GPIO pins (PA0-PA6) of the STM32 Blue Pill. Each digit is a bitmask written to the segment pins, with the current digit printed to the Serial Monitor every 800 ms.

Board	STM32 Blue Pill (STM32F103C8, Cortex-M3, 72 MHz)
Difficulty	beginner
Category	basics
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

// STM32 Blue Pill (F103) — 7-segment counter 0-9
// Segments A..G on PA0..PA6, common cathode (COM -> GND).
const int seg[7] = { PA0, PA1, PA2, PA3, PA4, PA5, PA6 }; // A B C D E F G
// Bit i (i=0..6) maps to segment seg[i]. 1 = segment lit.
const uint8_t pattern[10] = {
  0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F
};

void setup() {
  Serial.begin(115200);
  for (int i = 0; i < 7; i++) pinMode(seg[i], OUTPUT);
}

void loop() {
  for (int d = 0; d < 10; d++) {
    uint8_t p = pattern[d];
    for (int i = 0; i < 7; i++) digitalWrite(seg[i], (p >> i) & 1);
    Serial.print("digit = "); Serial.println(d);
    delay(800);
  }
}

How it works

Seven pins PA0-PA6 map to segments A-G, and a pattern array stores one bitmask per digit: 0x3F for 0, 0x06 for 1, and so on through 0x6F for 9. The loop walks digits 0-9, and for each one shifts the mask out bit by bit with (p >> i) & 1 to drive the seven segment pins.

The digitalWrite() per segment makes the code longer than an LCD sketch would be, but it shows exactly what a 7-segment driver does under the hood. The Serial print confirms the digit on the canvas matches the code’s intention, and the 800 ms delay gives each digit a readable pause.

Before you build it for real

Get the parts

Related examples

FAQ

How do the hex pattern values encode digits?

Each byte is a bitmask where bit i controls segment i (A..G on PA0..PA6). For example 0x3F = 0b0111111 lights segments A-F which spells 0, and 0x06 lights B and C which spells 1. The hex table is compact and standard — the same pattern arrays appear in Arduino, PIC and AVR libraries.

Why only 10 digits instead of 16?

The pattern table could easily include A-F for hex counting — the array just stops at 9. Extending it is a one-line table addition. The example keeps decimal counting to match the beginner level, but the display hardware itself does not care.