How to Make and Program a Custom STM32F103 PCB (LED Blink Test)

Designing your own STM32F103 PCB gives you full control over hardware — compact, power-efficient, and ready for production.
This complete guide walks through how to design and flash your custom STM32F103 board, finishing with an LED blink test using STM32CubeIDE and ST-Link V2.

Required Tools and Components

Hardware

• STM32F103C8T6 (LQFP48 package)
• 8 MHz crystal + 20pF capacitors
• 3.3V regulator (RT9193-33GB or AMS1117-3.3)
• LED + 330Ω resistor
• 10kΩ resistors (BOOT0, RESET)
• SWD 4-pin header
• Breadboard wires or PCB connectors
• ST-Link V2 programmer
• USB-to-UART module (CH340, CP2102, or FTDI)
• Multimeter, soldering tools, USB cable

Software

• STM32CubeIDE – Create, edit, and compile STM32 firmware
  👉 Download STM32CubeIDE
• STM32CubeProgrammer – Flash firmware to MCU
  👉 Download STM32CubeProgrammer

Step 1: Design the Core STM32F103 Circuit

The minimum working system for STM32F103 includes:

Step 2: Power Supply and Voltage Regulation

Use RT9193-33GB LDO regulator (as in your circuit):

• Input: 5V (from DC adapter)
• Output: Stable 3.3V
• Capacitors:
  • Input: 1µF
  • Output: 10µF
• Connect 3.3V to all VDD and VDDA pins
• Connect GND to all ground pins and planes

Step 3: Add Programming Debug Interfaces

Add a 4-pin header to connect the ST-Link V2:

BOOT0 should be tied to GND for normal operation.
Keep the SWDIO and SWCLK traces short (under 5 cm).

UART (Debugging)

Add a 3-pin header for UART communication:

You can connect this header to a USB-to-UART adapter (like CH340 or FTDI) for serial debugging in tools like PuTTY or Tera Term.

Step 4: PCB Layout Guidelines

• Keep the crystal and capacitors close to the MCU pins
• Place decoupling capacitors near every VDD pin
• Maintain a solid GND plane on the bottom layer
• Keep SWD and UART headers accessible on the board edge
• Place BOOT0 jumper and RESET button in easy reach
• Route TX/RX traces short and avoid noisy areas

Recommended Components

• MCU: STM32F103C8T6 (LQFP48)
• Crystal: 8MHz ±20ppm
• Regulator: RT9193-33GB
• Capacitors: 0.1µF × 4, 1µF × 1, 10µF × 1
• Resistors: 10kΩ (Reset, Boot0), 330Ω (LED)

Step 5: Generate Gerber Files

When your schematic and layout are done:

1. Run DRC (Design Rule Check)
2. Generate Gerber files (Top/Bottom Copper, Silkscreen, Solder Mask, Drill)
3. Export BOM (Bill of Materials)
4. Upload to a PCB manufacturer such as:
   • JLCPCB
   • PCBWay
   • Seeed Fusion

Step 6: Flashing Firmware (LED Blink)

Open STM32CubeIDE → Create new STM32 project (STM32F103C8Tx) → Enable:

• PC13 as GPIO Output (LED)
• PA9 / PA10 as USART1 TX/RX (Asynchronous Mode, 9600 baud)

Replace main.c with this code:

#include "main.h"
#include "usart.h"
#include "gpio.h"
#include <stdio.h>

int _write(int file, char *ptr, int len) {
  HAL_UART_Transmit(&huart1, (uint8_t*)ptr, len, HAL_MAX_DELAY);
  return len;
}

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART1_UART_Init();

  printf("STM32F103 Custom PCB Initialized\r\n");

  while (1)
  {
    HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_13);
    printf("LED toggled\r\n");
    HAL_Delay(1000);
  }
}

You can view UART output by opening a serial terminal (115200 baud, 8-N-1).

Step 7: Build and Upload

1. Connect ST-Link and power up your board
2. Click Run ▶ in STM32CubeIDE
3. STM32CubeProgrammer flashes the firmware automatically
4. Open your UART terminal — you should see:

STM32F103 Custom PCB Initialized
LED toggled
LED toggled

And your LED on PC13 blinks every 1 second 🎉

Troubleshooting

Step 8: Final Notes

You now have:

• A custom STM32F103 PCB
• ST-Link SWD programming interface
• UART debug capability (PA9/PA10)
• Working LED blink firmware

This foundation allows expansion to:

• I²C, SPI, and ADC sensors
• LoRa, BLE, or Wi-Fi modules
• Battery power and deep-sleep IoT designs

Project files on GitHub:
All design files, source code, and firmware for this custom STM32F103 PCB are available at the GitHub repository: github.com/Haipk001/Custom-STM32F1
Please make sure to download the latest files from the “Circuit” and “Core” folders before building or programming the board.