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@defgroup boards_common_blxxxpill Blackpill and Bluepill common code @ingroup boards_common @brief Support for cheap stm32f103c8 based boards such as bluepill and blackpill.

Overview

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.

Pinout

MCU

MCU	STM32F103C8 / STM32F103CB
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
UART	3
SPI	2
I2C	2
CAN	1
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

Flashing

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-stm32f103c8 flash

Or for the blackpill with:

$ make BOARD=blackpill-stm32f103c8 flash

Additional Flash

Typically, the STM32F103C8 does actually have 128 KiB flash. To make use of this, just flash with

$ make BOARD=bluepill-stm32f103cb flash

Or for the blackpill with:

$ make BOARD=blackpill-stm32f103cb 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.

In order to flash the *cb variant onto *c8 hardware requires OpenOCD in version 0.11 or later.

Connecting via Serial

The default UART port used is UART1, which uses pins A9 (TX) and A10 (RX). To use it, configure your UART to operate at a symbol rate of 115200 baud, 1 stop bit and no parity (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
SWDIO	DIO
SWCLK	DCLK
NRST	R
GND	GND
VDD (3.3V) (*)	3.3
Target VCC (**)	3.3

(*) Most debuggers have a 3.3V supply voltage to power the board. You can alternatively power the board using the TTL-Adapter or via Micro-USB.
(**) Some debuggers monitor the voltage of the target MCU. Their target VCC pin needs to be connected to one of the 3.3V pins of the boards.

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.