Blackpill and Bluepill common code

Support for cheap stm32f103c8 based boards such as bluepill and blackpill. More...

Detailed Description

Support for cheap stm32f103c8 based boards such as bluepill and blackpill.


The bluepill and the blackpill are STM32F103 based board which can be bought for around 2€ on sides like AliExpress, eBay and others. Although the STM32F130C8 MCU nominally has 64 KiB flash, most actually have 128 KiB flash.

There are also versions that only report to have 32 KiB, but actually have 64 KiB.




Family ARM Cortex-M3
Vendor STMicroelectronics
RAM 20 KiB
Flash 32 KiB/ 64 KiB / 128 KiB
Frequency up to 72 MHz
Timer 3x 16-Bit
ADC 2x 12-bit, 10 channels
I2C 2
Vcc 2.0 to 3.6 V
Datasheet Datasheet

Implementation Status

ID Supported
GPIO yes
PWM yes
UART yes
ADC yes
I2C yes
SPI yes
USB no
Timer yes
CAN no


To program and debug the board you need a SWD capable debugger. The easiest way is using OpenOCD. By default RIOT uses the hardware reset signal and connects to the chip under reset for flashing. This is required to reliably connect to the device even when the MCU is in a low power mode. Therefore not only SWDIO and SWCLK, but also the RST pin of your debugger need to be connected to the board. Once the device is connected to the debugger and OpenOCD is installed, you can flash the device with:

$ make BOARD=bluepill flash

Or for the blackpill with:

$ make BOARD=blackpill flash

Additional Flash

To make use of the entire 128 KiB flash, compile and flash your application with:

$ make BOARD=bluepill-128kib flash

Or for the blackpill with:

$ make BOARD=blackpill-128kib flash

This sets the CPU_MODEL make variable to stm32f103cb, the default value is stm32f103c8. These two CPU models basically only have one major difference, the former has 128 KiB flash while the latter has 64 KiB.

Flashing for the 128KiB version currently (as of September 2019) requires the development version of OpenOCD.

Connecting via Serial

The default UART port used is UART2, which uses pins A2 (TX) and A3 (RX). To use it, configure your UART to operate at a baudrate of 115200/8N1.

Using PWM

PWM is available at pins A8 to A11.

Known Issues

USB connector

The Micro-USB port is sometimes not soldered properly. Also, it is usually equipped with an incorrect resistor. This can be fixed multiple ways.

Flashing fails

Please check whether the debugger is properly connected, including the hardware reset signal pin.

Pin on Debugger Pin on Blue Pill
VDD (3.3V) (*) 3.3
Target VCC (**) 3.3

Most very cheap SWD debuggers (especially those imported for about 2€ from far east) do not have a Target VCC pin; they will still work just fine. On these cheap debuggers the pin to send the reset signal to the board is often either not present or defunct. You can work around this by pressing the reset button when OpenOCD wants to connect to the Blue Pill. Hit the reset button again after flashing in order to boot the newly flashed image.

Where to buy

The board is sold under different names. On some sites it is called bluepill or blue pill. On others you might find it by searching for stm32f103c8 or stm32f103c8t6.

Try eBay or AliExpress.

Further reading


file  board_common.h
 Peripheral MCU configuration for the bluepill/blackpill board.
file  gpio_params.h
 Board specific configuration of direct mapped GPIOs.
file  periph_conf.h
 Peripheral MCU configuration for the bluepill/blackpill boards.