Documentation

// STM32 Blue Pill - Blink on-board LED (PC13, active LOW)
// Install: Boards Manager -> "STM32 MCU based boards" by STMicroelectronics
// Select Board: "Generic STM32F1 series" -> Board part number "BluePill F103C8"
// Upload Method: "STM32CubeProgrammer (SWD)" if using ST-LINK
//                "STM32CubeProgrammer (Serial)" if using USB-TTL

void setup() {
  pinMode(PC13, OUTPUT);
}

void loop() {
  digitalWrite(PC13, LOW);   // LED on (active LOW)
  delay(500);
  digitalWrite(PC13, HIGH);  // LED off
  delay(500);
}

// STM32 Blue Pill - read a 10k potentiometer on PA0 (ADC channel 0)
// Wire pot ends to 3V3 and GND, wiper to PA0

const int potPin = PA0;

void setup() {
  Serial.begin(115200);
  pinMode(potPin, INPUT_ANALOG);
  analogReadResolution(12);   // 0 - 4095
}

void loop() {
  int raw = analogRead(potPin);
  float voltage = raw * 3.3 / 4095.0;
  Serial.print("Raw=");  Serial.print(raw);
  Serial.print("  V="); Serial.println(voltage, 3);
  delay(200);
}

// STM32 Blue Pill - scan I2C1 bus (SDA=PB7, SCL=PB6)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin();   // I2C1 on default pins PB6/PB7
  delay(500);
  Serial.println("STM32 Blue Pill I2C Scanner");
}

void loop() {
  byte found = 0;
  for (byte addr = 1; addr < 127; addr++) {
    Wire.beginTransmission(addr);
    if (Wire.endTransmission() == 0) {
      Serial.print("  Found device at 0x");
      if (addr < 16) Serial.print('0');
      Serial.println(addr, HEX);
      found++;
    }
  }
  if (found == 0) Serial.println("  No I2C devices found");
  Serial.println("---");
  delay(3000);
}

/* STM32CubeIDE auto-generates main.c when you make a project for STM32F103C8.
 * Configure PC13 as GPIO_Output in the .ioc file, then drop this in the loop. */

#include "main.h"

int main(void) {
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();

  while (1) {
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_RESET); // LED on
    HAL_Delay(500);
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_SET);   // LED off
    HAL_Delay(500);
  }
}