STM32 Blue Pill & STM32F103

Digital GPIO Pins (PA0 - PB15, PC13 - PC15)

37 GPIO pins operating at 3.3V logic. Most pins accept up to 5V inputs without damage.

• Pins marked FT (Five-volt Tolerant) include PA8–PA15, PB3, PB4, PB6–PB9, PB12–PB15
• Pin PC13 connects to the onboard green/blue user LED (active LOW)
• Pins PA9 and PA10 serve as the primary USART1 serial programming interface

Dual 12-bit ADCs (ADC1 & ADC2)

10 external analog channels capable of synchronized dual-ADC simultaneous conversions.

• Channels ADC0 to ADC9 located on pins PA0 through PA7 and PB0, PB1
• Full 12-bit conversion delivers 0–4095 digital counts across 0V to 3.3V
• Direct connection to multi-channel DMA for autonomous analog sensor streaming

Hardware Communication & Debug

Multi-channel serial controllers, automotive CAN bus, and debug ports.

• 3 hardware USARTs, 2 SPI interfaces (up to 18 MHz), and 2 I2C interfaces (up to 400 kHz)
• Hardware CAN 2.0B bus on pins PB8 (RX) and PB9 (TX)
• SWD header pins: PA13 (SWDIO) and PA14 (SWCLK) for ST-Link programming

Hardware USART (x3)

PA9/PA10, PA2/PA3, PB10/PB11

Three independent serial ports supporting baud rates up to 4.5 Mbps with hardware RTS/CTS flow control.

Hardware SPI (x2)

SPI1 (18 MHz) & SPI2 (9 MHz)

High-speed SPI buses with DMA support for driving graphical LCD screens, high-speed ADCs, and SD cards.

Hardware I2C (x2)

I2C1 (PB6/PB7) & I2C2 (PB10/PB11)

Dual I2C buses supporting Standard and Fast (400 kHz) modes with SMBus and PMBus protocol compliance.

CAN 2.0B Controller

PB8 (CAN_RX) & PB9 (CAN_TX)

Automotive Controller Area Network peripheral with 14 filter banks, supporting 11-bit standard and 29-bit extended frames.

USB 2.0 Full Speed

PA11 (USB D-) & PA12 (USB D+)

12 Mbps on-chip USB peripheral for emulating virtual COM ports, USB MIDI keyboards, or mass storage devices.

SWD Debug Port

PA13 (SWDIO) & PA14 (SWCLK)

Two-pin ARM Serial Wire Debug protocol interface providing full hardware breakpoints and register stepping.

Connect 4 wires (3.3V, GND, SWDIO, SWCLK) from an ST-Link V2 programmer to the Blue Pill header. Flash firmware instantly in VS Code or STM32CubeProgrammer.

Pro tip: SWD flashing bypasses the USB bootloader completely and allows setting live hardware breakpoints in GDB.

Stream ADC conversions or UART buffers directly into SRAM without any CPU execution intervention using the 7-channel DMA controller.

Pro tip: Using DMA with ADC eliminates sampling jitter and frees 100% of CPU cycles for real-time control algorithms.

Many budget clone Blue Pill boards feature an incorrect 10kΩ or 4.7kΩ pull-up resistor on the USB D+ line (R10) instead of the required 1.5kΩ resistor.

Pro tip: If your computer fails to recognize the Blue Pill USB device, replace R10 or solder a 1.5k–1.8k resistor between PA12 and 3.3V.

The Cortex-M3 NVIC supports 16 programmable priority levels and sub-priorities, delivering ultra-low interrupt latency down to 12 clock cycles.

Pro tip: Higher priority interrupts can preempt lower priority ISRs, guaranteeing deterministic timing for motor shutoffs.

Pair the Blue Pill’s onboard CAN controller with an inexpensive MCP2551 or TJA1050 5V transceiver to read vehicle OBD-II diagnostics frames.

Pro tip: Remember to terminate both ends of the CAN bus with 120Ω resistors between CAN-H and CAN-L.

Although labeled as STM32F103C8 (rated for 64 KB), the overwhelming majority of genuine ST silicon contains 128 KB of working physical Flash memory.

Pro tip: You can safely modify your linker script from 64K to 128K on almost all Blue Pill boards.

High-Speed Motor & Inverter Control

Advanced timer 1 generates complementary 3-phase PWM signals with programmable dead-time insertion for brushless DC (BLDC) motor drivers.

Automotive & CAN Bus Nodes

Built-in CAN 2.0B active controller interfaces directly with vehicle onboard diagnostics (OBD-II) networks and automotive telemetry.

USB Audio & MIDI Devices

Native USB 2.0 Full-Speed device controller enables low-latency USB MIDI keyboards, synthesized tone generators, and custom HID devices.

High-Precision Oscilloscopes & DAQs

Dual 12-bit 1 MSPS ADCs paired with circular DMA buffers sample analog signals at high frequencies without consuming CPU execution cycles.

// STM32 Blue Pill - Multi-channel 12-bit ADC Reading
const int sensorPin1 = PA0;
const int sensorPin2 = PA1;
const int ledPin = PC13; // Onboard LED (Active LOW)

void setup() {
  Serial.begin(115200);
  pinMode(ledPin, OUTPUT);
  
  // Set 12-bit ADC resolution (0 - 4095)
  analogReadResolution(12);
  Serial.println("STM32 Blue Pill 12-bit ADC Ready");
}

void loop() {
  int raw1 = analogRead(sensorPin1);
  int raw2 = analogRead(sensorPin2);

  float volt1 = raw1 * (3.3 / 4095.0);
  float volt2 = raw2 * (3.3 / 4095.0);

  Serial.printf("PA0: %d (%.3fV) | PA1: %d (%.3fV)\n", raw1, volt1, raw2, volt2);

  digitalWrite(ledPin, LOW);  // Turn ON LED
  delay(100);
  digitalWrite(ledPin, HIGH); // Turn OFF LED
  delay(900);
}

// STM32F103 - Direct Register Access Blink (Zero HAL Overhead)
#include "stm32f10x.h"

void delay_cycles(volatile uint32_t count) {
  while (count--) { __NOP(); }
}

int main(void) {
  // 1. Enable GPIOC clock in RCC APB2ENR register
  RCC->APB2ENR |= RCC_APB2ENR_IOPCEN;

  // 2. Configure PC13 as Output Push-Pull @ 2 MHz
  GPIOC->CRH &= ~(0xF << 20); // Clear CNF13 & MODE13
  GPIOC->CRH |= (0x2 << 20);  // Output 2MHz, Push-Pull

  while (1) {
    GPIOC->BSRR = (1 << 13);  // Turn OFF PC13 LED (Active LOW)
    delay_cycles(1000000);
    GPIOC->BRR  = (1 << 13);  // Turn ON PC13 LED
    delay_cycles(1000000);
  }
}