How to use Platformio to develop for generic STM32F103C8 board (a.k.a. BluePill) with Arduino framework

Courtecy of Hackaday.com

In case you'd like to learn how to program this board in C with debugging capability, thus completely purging Arduino ecosystem from your life, check my other blog post out.

This post describes a step in moving on from Arduino ecosystem for Arduino-addicted fellows out there. After completing this guide, you'll almost break your crippling Arduino dependency by replacing Arduino IDE with PlatformIO plugin for Github Atom IDE, and Arduino boards with generic mass-produced board with STM32 microcontroller.

I couldn't find a decent one-piece manual online on the topic, so here goes:

You'll need

• The Blue pill (can be procured on eBay, Aliexpress etc.).
  
  

  

  And at a reasonable price, as well!

  
• STLink v2 programmer clone (same place, almost the same price range).
  
  
  
  
  
  
• A computer that can run Atom IDE , hopefully without too much lagging.

Step-by-step manual

Okay, now that you've got everything on the list, we can start uploading some sample code to the blue pill.

First off, follow the MANUAL (steps I. Atom and, optionally, II. Clang for Intelligent Code Completion) to install Github's Atom IDE and Platformio, which is a plugin for Atom. Code completion will just assist you while you type your code and is not essential.

Then do the Setting Up the Project paragraph. As soon as you've copy-pasted the example code, you should define LED_BUILTIN as PC13 - that's where the blue pill has its blinky thing connected.
The complete mapping of physical pins to Arduino pins can be seen on this handy pic:

All that's left now is to configure the project to use Arduino framework and STLink to upload the resulting code. For that, your platformio.ini should look like this:

Your Blink project should be able to successfully build now:

Build and upload buttons are located on the vertical pane on the left corner.

Try to upload now! Connect STLink to BluePill's programming pin header as follows:

STLink pin	BluePill pin
GND (3 or 4)	GND
3.3V (7 or 8)	3.3
SWDIO (2)	DIO
SWCLK(6)	DCLK

Connections for in-circuit programming

Upload should be successful now and LED should blink. In some cases, you'll see this instead:
To fix that, short the BOOT0 pin to 3.3V with a jumper (consult the pinout diagram again) and reset the microcontroller. You'll be able to upload again after that.

The mode in which STM32 starts is determined by pins BOOT0 and BOOT1 :

BOOT1	BOOT0	Boot mode
X	0	User Flash memory
0	1	System memory (bootloader)
1	1	Embedded SRAM

You'll have to reset the board again in bootloader mode to be able to upload again. Therefore, my workflow with bluepill is like this:

1. Set Bluepill to bootloader mode with jumpers.
2. Upload my code, check if it works
3. If it doesn't, reset Bluepill, fix the code and go to step 2.
4. If everything is fine, Set Bluepill to run my code at startup with jumpers.

Libraries, serial monitor, and all the goodies we love in Arduino IDE

Blinking the LED isn't all we do with microcontrollers, and eventually you have to program more advanced peripherals that GPIO. That's where Arduino steps in with its huge ecosystem of libraries to every taste.

What do we have in Platformio? Turns out, almost as much libraries as in Arduino.

GUI interface in PlatformIO is available too!

Now, as for Serial ports, I decided to find which is which experimentally. First, I uploaded the following code to my Blue Pill: To get USB Serial working, I soldered a 1.5k resistor between 3.3V and PA12, while also desoldering R10 from PCB.

Then I got my USB to Serial converter and connected it to Blue Pill's Serial lines like so:

USB to Serial pin	BluePill pin
GND	GND
RX	A9 (TX)
TX	A10 (RX)

UART-to-Serial connected to BluePill

Now let's see if we can receive something in Putty:

Serial object works with pins A9 and A10

Aand USB serial on miniUSB connector where it should be.

The result of investigation is that there are two ways to use serial communication on Blue Pill:

Arduino object	Physical interface on BluePill
usb	microUSB connector
Serial	pins A9 and A10

That's all you'll need to get a jump start on using Arduino Framework on Bluepill! From now on, you can increase software complexity of your Bluepill prototypes much faster thanks to Arduino API.