Documentation

Overview

The STM32F103C8T6 "Blue Pill" is a 32-bit ARM Cortex-M3 development board built around ST Microelectronics' STM32F103C8T6 chip. Running at 72 MHz with 64 KB of Flash and 20 KB of SRAM, it is significantly more powerful than a classic ATmega328 Arduino while staying in a breadboard-friendly form factor. It is an excellent step up when your Arduino projects start running out of speed, memory, or peripherals.

This pre-soldered version comes with headers and a Micro-USB connector already installed so you can plug it in, program it, and start prototyping. The chip exposes up to 37 GPIO, multiple UART / SPI / I2C / CAN peripherals, 10 channels of 12-bit ADC, and PWM on nearly every pin. Onboard hardware includes a user LED on PC13, reset button, BOOT0 / BOOT1 jumpers for selecting the boot mode, an 8 MHz main crystal, and a 32.768 kHz RTC crystal.

This manual covers the full pinout, Boot mode configuration, programming via ST-Link / USB DFU / UART, wiring against Arduino / ESP32 / Raspberry Pi as an external programmer, a working "blink + serial" Arduino example, and FAQs about the Arduino IDE setup and common first-time issues.

At a Glance

Specifications

Pinout Diagram

Wiring Guide

The Blue Pill can be programmed three main ways: via an ST-Link V2 through its 4-pin SWD header (most reliable), via USB DFU after flashing a bootloader, or via a USB-to-TTL adapter on UART1 (PA9 / PA10) using the factory ROM bootloader. The tables below show each option.

Code Examples

Most users program the Blue Pill with the Arduino IDE plus the official STM32 core. Below is a full "blink + serial" example that toggles the PC13 LED and prints a counter over Serial1 (the USART that maps to PA9 TX / PA10 RX). Open the Serial Monitor at 9600 baud to see output.

Arduino (STM32duino Core)

// Blue Pill blink + serial counter.
// Board in Arduino IDE: "Generic STM32F1 series" -> "BluePill F103C8"
// Upload method: STM32CubeProgrammer (Serial) or ST-Link.

#define LED_PIN PC13  // Onboard LED (active LOW)

void setup() {
  pinMode(LED_PIN, OUTPUT);
  Serial1.begin(9600);   // PA9 TX / PA10 RX
  Serial1.println("Blue Pill awake");
}

uint32_t counter = 0;

void loop() {
  digitalWrite(LED_PIN, LOW);   // LED on
  delay(500);
  digitalWrite(LED_PIN, HIGH);  // LED off
  delay(500);

  Serial1.print("Blink #");
  Serial1.println(counter++);
}

Reading an Analog Pin (ADC)

// Read a potentiometer (or any 0-3.3V signal) on PA0.
// The STM32 ADC is 12-bit (0-4095), unlike Arduino's 10-bit.

const int POT_PIN = PA0;

void setup() {
  analogReadResolution(12);  // Use the full 12 bits
  pinMode(POT_PIN, INPUT_ANALOG);
  Serial1.begin(9600);
}

void loop() {
  int raw = analogRead(POT_PIN);
  float volts = raw * (3.3f / 4095.0f);

  Serial1.print("Raw: "); Serial1.print(raw);
  Serial1.print(" | V: "); Serial1.println(volts, 3);
  delay(200);
}

Flashing with stm32flash (Raspberry Pi / Linux)

# 1. Install stm32flash:
sudo apt update
sudo apt install stm32flash

# 2. Wire Pi UART to STM32 PA9/PA10 as shown in the wiring table.
# 3. Move BOOT0 jumper to 1 and press RESET on the Blue Pill.

# 4. Write firmware.bin starting at the Flash base address:
sudo stm32flash -w firmware.bin -v -g 0x8000000 /dev/serial0

# 5. Move BOOT0 jumper back to 0 and press RESET to run your firmware.

Frequently Asked Questions

Related Tutorials