Serial Wire Debug
PA13 is SWDIO and PA14 is SWCLK. The 3.3 V board rail is a reference for a compatible probe.
Blue Pill pinout
The documented blue PCB has two 20-contact headers, SWD and Micro USB. Its PC13 user LED is active low. The USB D+ pull-up varies across production boards.
STM32F103C8T6 Blue Pill
49 contacts Current packageSTM32F103C8T6 Blue Pill pinout
Header 1
Header 2
SWD header
USB connector
H4-3 · D+
USB data line. PCB net destination is PA12.
All 49 pins
| Pin | Signal | Direction | Function |
|---|---|---|---|
| H1-1 | VB Power | Power | Connects to VBAT. Use the specified board power connection. |
| H1-2 | C13 Configurable I/O | Configurable I/O | Routes to MCU PC13. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-3 | C14 Configurable I/O | Configurable I/O | Routes to MCU PC14. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-4 | C15 Configurable I/O | Configurable I/O | Routes to MCU PC15. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-5 | A0 Configurable I/O | Configurable I/O | Routes to MCU PA0. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-6 | A1 Configurable I/O | Configurable I/O | Routes to MCU PA1. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-7 | A2 Configurable I/O | Configurable I/O | Routes to MCU PA2. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-8 | A3 Configurable I/O | Configurable I/O | Routes to MCU PA3. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-9 | A4 Configurable I/O | Configurable I/O | Routes to MCU PA4. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-10 | A5 Configurable I/O | Configurable I/O | Routes to MCU PA5. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-11 | A6 Configurable I/O | Configurable I/O | Routes to MCU PA6. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-12 | A7 Configurable I/O | Configurable I/O | Routes to MCU PA7. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-13 | B0 Configurable I/O | Configurable I/O | Routes to MCU PB0. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-14 | B1 Configurable I/O | Configurable I/O | Routes to MCU PB1. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-15 | B10 Configurable I/O | Configurable I/O | Routes to MCU PB10. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-16 | B11 Configurable I/O | Configurable I/O | Routes to MCU PB11. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H1-17 | R Active-low reset | Active-low reset | Connects to MCU NRST. Use a compatible open-drain reset signal. |
| H1-18 | 3.3 Power | Power | Connects to 3V3. Use the specified board power connection. |
| H1-19 | G Return | Return | Connects to the board’s ground plane. |
| H1-20 | G Return | Return | Connects to the board’s ground plane. |
| H2-1 | 3.3 Power | Power | Connects to 3V3. Use the specified board power connection. |
| H2-2 | G Return | Return | Connects to the board’s ground plane. |
| H2-3 | 5V Power | Power | Connects to 5V. Use the specified board power connection. |
| H2-4 | B9 Configurable I/O | Configurable I/O | Routes to MCU PB9. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-5 | B8 Configurable I/O | Configurable I/O | Routes to MCU PB8. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-6 | B7 Configurable I/O | Configurable I/O | Routes to MCU PB7. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-7 | B6 Configurable I/O | Configurable I/O | Routes to MCU PB6. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-8 | B5 Configurable I/O | Configurable I/O | Routes to MCU PB5. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-9 | B4 Configurable I/O | Configurable I/O | Routes to MCU PB4. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-10 | B3 Configurable I/O | Configurable I/O | Routes to MCU PB3. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-11 | A15 Configurable I/O | Configurable I/O | Routes to MCU PA15. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-12 | A12 Configurable I/O | Configurable I/O | Routes to MCU PA12. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-13 | A11 Configurable I/O | Configurable I/O | Routes to MCU PA11. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-14 | A10 Configurable I/O | Configurable I/O | Routes to MCU PA10. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-15 | A9 Configurable I/O | Configurable I/O | Routes to MCU PA9. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-16 | A8 Configurable I/O | Configurable I/O | Routes to MCU PA8. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-17 | B15 Configurable I/O | Configurable I/O | Routes to MCU PB15. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-18 | B14 Configurable I/O | Configurable I/O | Routes to MCU PB14. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-19 | B13 Configurable I/O | Configurable I/O | Routes to MCU PB13. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H2-20 | B12 Configurable I/O | Configurable I/O | Routes to MCU PB12. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H3-1 | 3V3 Power | Power | Connects to 3V3. Use the specified board power connection. |
| H3-2 | DIO Configurable I/O | Configurable I/O | Routes to MCU PA13. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H3-3 | CLK Configurable I/O | Configurable I/O | Routes to MCU PA14. Choose the applicable GPIO or peripheral function in the MCU documentation. |
| H3-4 | GND Return | Return | Connects to the board’s ground plane. |
| H4-1 | VBUS Power | Power | Connects to 5V. Use the specified board power connection. |
| H4-2 | D- Bidirectional | Bidirectional | USB data line. PCB net destination is PA11. |
| H4-3 | D+ Bidirectional | Bidirectional | USB data line. PCB net destination is PA12. |
| H4-4 | ID Unconfirmed | Unconfirmed | The board source supplies no net for this position. Consult the schematic before use. |
| H4-5 | GND Return | Return | Connects to the board’s ground plane. |
Signal assignments
USART1 on PA9/PA10
PA9 is TX and PA10 is RX in the default USART1 mapping. Select the matching firmware configuration.
Electrical limits
| Parameter | Limit | Conditions and source |
|---|---|---|
| Board logic rail3.3 V nominal | 3.3 V nominal | Check the fitted regulator and MCU datasheet before attaching an external circuit. USB is the only supply used in the example. STM32F103C8T6 Blue Pill connector map |
| External high-speed oscillator8 MHz | 8 MHz | Use the correct HSE frequency in firmware clock calculations. STM32F103C8T6 Blue Pill connector map |
Models and documents
The maps follow the listed PCB variants. Match the board markings and connector positions to the referenced schematic before applying power.
- STM32F103C8T6 Blue Pill
- The documented blue PCB has two 20-contact headers, SWD and Micro USB. Its PC13 user LED is active low. The USB D+ pull-up varies across production boards.
- STM32-base · STM32F103C8T6 Blue Pill· Board identification, connector numbering and documented net destinations.
- STMicroelectronics MCU datasheet· MCU electrical specifications and package pin functions.
- STM32F103C8T6 Blue Pill schematic· PCB power, debug, connector and peripheral wiring.