STM32 “blue pill” easy development with Mbed

The "blue pill" is an STM32F103 based development board. Although it is less popular, the board is cheaper than an Arduino Nano. More than that, STM32F103 is a device with Cortex-M3 ARM CPU that runs at 72 MHz, 20 kB of RAM and 64 or 128 kB of flash memory. The microcontroller (MCU) has USB port, two serial ports, 16 bit PWM pins and 12 bit ADC pins. It runs at 3.3V, but some of its pins are 5V tolerant.

I tried to program this development board using both Arduino IDE and STM32 HAL, but I wasn’t quite satisfied. Arduino framework is simplified and does not take advantage of platform’s features, while HAL was quite difficult for me. Using HAL in Eclipse come with another disadvantage: direct uploading of the binary in flash didn’t work, so I had to use ST-Link tools to upload it, outside of Eclipse. Recently I heard of PlatformIO IDE. This is a development environment supplied as Visual Studio Code or Atom plugin. One of its great advantages is the support for more than 500 development boards! Although VS Code and Atom are cross platform software, they are not at all lightweight, so you’ll need rather good hardware to run them smoothly.

Another great feature of PlatformIO is that for a development board you have multiple framework options. You can program the bluepill using Arduino API, just as you would do in Arduino IDE. Or you can program it using STM32Cube API. But, there is also Mbed OS framework, which I found it to be quite easy to develop.