# STM32 Blue Pill (F103C8T6): specs and pinout

> A small development board built around the STM32F103C8T6 (Arm Cortex-M3, 72 MHz). There is no ST or maker document for the board itself; this page…

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A small development board built around the STM32F103C8T6 (Arm Cortex-M3, 72 MHz). There is no ST or maker document for the board itself; this page gives the chip facts only.

Every value cites its sourceChip-level pinout

[Buy on Compoden](https://compoden.com/products/stm32-blue-pill-f103c8t6)

## Specs

| Spec | Value | Source |
|---|---|---|
| MCU core | Arm 32-bit Cortex-M3, 72 MHz maximum | source DS5319 Rev 20, Features (p.1) |
| Memory (C8 variant) | 64 KB flash (the datasheet covers 64 or 128 KB), 20 KB SRAM | source Features (p.1); Table 1 Device summary |
| Supply (application and I/Os) | 2.0 V to 3.6 V | source Features (p.1) |
| 5 V tolerance | Almost all I/Os are 5 V tolerant (Features); the pin table marks 5 V tolerant pins FT and leaves the level blank for the others | source Features (p.1); Table 5 I/O level column |
| ADC | 2 x 12-bit, 1 us, up to 16 channels, conversion range 0 to 3.6 V | source Features (p.1) |
| Communication | Up to 2 I2C, 3 USART, 2 SPI, CAN 2.0B, USB 2.0 full-speed | source Features (p.1) |
| Ambient temperature | -40 to 85 C (suffix 6) or -40 to 105 C (suffix 7) | source Table 2 medium-density device features, Operating temperatures row; Table 9 General operating conditions |
| Debug | Serial wire debug (SWD) and JTAG | source Features (p.1) |

## Power

| | Value | Source |
|---|---|---|
| Supply | Chip VDD 2.0 V to 3.6 V; the board's own regulator and USB supply are not covered by a maker document | source Features (p.1) |

## Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.

Chip pin functions only (STM32F103C8 LQFP48 pin table). This is a selection of 18 chip pins, not a header map: the board itself (regulator, USB connector, crystals, header order, jumpers, LED) is not covered by an official document, and pins such as PA0, PA1, PB0, PB1 and PC13 are not listed. Match the rows to your board's silkscreen yourself.

| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| PA2 | USART2_TX (default); TIM2_CH3 | | No FT mark in the level column: not 5 V tolerant | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA3 | USART2_RX (default); TIM2_CH4 | | No FT mark in the level column: not 5 V tolerant | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA4 | SPI1_NSS; USART2_CK; ADC12_IN4 | | No FT mark in the level column: not 5 V tolerant | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA5 | SPI1_SCK; ADC12_IN5 | | No FT mark in the level column: not 5 V tolerant | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA6 | SPI1_MISO; ADC12_IN6; TIM3_CH1 | | No FT mark in the level column: not 5 V tolerant | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA7 | SPI1_MOSI; ADC12_IN7; TIM3_CH2 | | No FT mark in the level column: not 5 V tolerant | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA9 | USART1_TX; TIM1_CH2 | | FT (5 V tolerant) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA10 | USART1_RX; TIM1_CH3 | | FT (5 V tolerant) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA11 | USBDM; USART1_CTS; CANRX; TIM1_CH4 | | FT (5 V tolerant) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA12 | USBDP; USART1_RTS; CANTX; TIM1_ETR | | FT (5 V tolerant) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA13 | JTMS / SWDIO | | FT (5 V tolerant); debug pin after reset | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PA14 | JTCK / SWCLK | | FT (5 V tolerant); debug pin after reset | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PB6 | I2C1_SCL; TIM4_CH1 | | FT (5 V tolerant) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PB7 | I2C1_SDA; TIM4_CH2 | | FT (5 V tolerant) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PB10 | I2C2_SCL; USART3_TX; TIM2_CH3 | | FT (5 V tolerant) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| PB11 | I2C2_SDA; USART3_RX; TIM2_CH4 | | FT (5 V tolerant) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| BOOT0 | Boot mode select input | | Input pin; boot pin of the chip | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |
| NRST | Reset (input/output) | | Reset pin of the chip (input/output) | source Table 5 Medium-density STM32F103xx pin definitions (p.28-32) |

## Build with it
Project ideas for the STM32 Blue Pill (F103C8T6). Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.

- [A tilt angle readout over serial with an STM32 Blue Pill and an MPU6050 module](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20tilt%20angle%20readout%20over%20serial%20with%20an%20STM32%20Blue%20Pill%20and%20an%20MPU6050%20module): The chip I2C1 pins are PB6 (SCL) and PB7 (SDA) at 3.3 V logic; power the MPU6050 module from 3.3 V so both ends use the same level.
- [A pressure and temperature display with an STM32 Blue Pill, a BMP280 module and a 0.96 inch OLED](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20pressure%20and%20temperature%20display%20with%20an%20STM32%20Blue%20Pill%2C%20a%20BMP280%20module%20and%20a%200.96%20inch%20OLED): Both I2C modules can share PB6 and PB7 or use I2C2 on PB10 and PB11; use 3.3 V supply and check each module's address.
- [A knob controlled servo with an STM32 Blue Pill, a 10k potentiometer and an SG90 servo](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20knob%20controlled%20servo%20with%20an%20STM32%20Blue%20Pill%2C%20a%2010k%20potentiometer%20and%20an%20SG90%20servo): The potentiometer wiper goes to an ADC pin such as PA0 between 0 V and 3.3 V; the servo signal comes from a timer pin such as PA6 and the servo needs its own 5 V supply with grounds joined.
- [A serial data logger clock with an STM32 Blue Pill and a DS3231 module](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20serial%20data%20logger%20clock%20with%20an%20STM32%20Blue%20Pill%20and%20a%20DS3231%20module): The DS3231 talks I2C on PB6 and PB7 and keeps time on its own battery; timestamps are sent over USART1 on PA9 and PA10 to a USB-serial adapter.

## Common mistakes

- Putting 5 V on a pin that is not 5 V tolerant, or on VDD: the supply is 2.0 V to 3.6 V and only pins marked FT tolerate 5 V (source: [link](https://www.farnell.com/datasheets/4595259.pdf), Features p.1 and Table 5)
- Feeding more than 3.6 V to an ADC input: the conversion range is 0 to 3.6 V (source: [link](https://www.farnell.com/datasheets/4595259.pdf), Features p.1)
- Using PA11 and PA12 for GPIO while also using USB: those pins are the USB DM and DP lines of the chip (source: [link](https://www.farnell.com/datasheets/4595259.pdf), Table 5)

## Not covered by the official source

- No ST or maker document exists for the Blue Pill board itself (it is a third-party design), so supply, regulator, header and LED facts are not written.
- Only a subset of chip pins is listed, taken from the datasheet pin table.
- Electrical characteristics tables (current, ADC accuracy, I/O drive) are not given on this page.
- Values are from datasheet Rev 20 (Jul 2025), a hosted copy of the ST document.

## Sources

- [link](https://www.farnell.com/datasheets/4595259.pdf) (STM32F103x8/xB datasheet DS5319 Rev 20, Jul 2025)