Article by:
Date Published:
Last Modified:


PlatformIO is a cross-platform CLI tool and IDE extension (primarily for Visual Studio Code) that allows you to build and upload firmware to embedded devices. Unlike other tools such as Arduino, mbed or Zephyr, it is purely a build tool and does not provide it’s own API (framework) that you can call when writing firmware. Instead, it supports a number of frameworks including Arduino, mbed and Zephyr. It is designed to automatically pull down, install and run the toolchains/compilers required to compile your firmware for the target architecture so that you don’t have to manage these yourself.

The logo for PlatformIO. Retrieved from on 2021-03-10.

The logo for PlatformIO. Retrieved from on 2021-03-10.

PlatformIO Core is the command-line tool that contains most of PlatformIO’s core logic (the IDE makes calls to this). PlatformIO IDE is an extension to Visual Studio Code which provides GUI access to the functions provided by PlatformIO Core, as well as the usual text editing and syntax highlighting.


  • board: A physical PCB containing a microcontroller that code can be built for and programmed.
  • platform: Examples of platforms include atmelavr, atmelsam, and ststm32. A platform uses packages. Default install directory for platforms is core_dir/platforms.
  • package: A package is a tool of framework that can be used when compiling one or more platforms. Default install directory for packages is core_dir/packages.
  • framework: A firmware “framework” providing an API to call from your application to interface with hardware peripherals and device drivers (a HAL). Available options include arduino, mbed, zephyr.


You can install the PlatformIO core via pip:

$ pip install -U platformio

You can install PlatformIO as an Extension in Visual Studio Code. If you do this, you do not need to install the CLI tool separately as it is bundled with the extension. However, you will only be able to call pio via the command line through a special “PlatformIO” terminal instance. If you want to call pio from any command-line instance, add:


to your PATH. For example, on Windows you would add something similar to C:\Users\<username>\.platformio\penv\Scripts to your system PATH.

Library Dependency Finder (LDF)

For more info on the LDF, see

Local libraries can be stored in the lib/ directory.

How To Create A PlatformIO Project

Create a new project in the current directory:

pio project init --board uno

Build the project:

pio run

PlatformIO Project Directory Structure

lib/   This is intended for project specific libraries. PlatformIO will automatically compile all projects in this directory as static libraries and then link them into the main executable. git submodules is a good way on managing libraries in this directory.
|--my_lib_1/    // Example of a simple standalon lib which is not itself a PlatformIO project
   |--main.cpp  // Source code directory in library root dir
|--my_lib_2/    // Example of a lib which is it's own self-contained PlatformIO project
test                // Directory which contains test files
  |--test_main.cpp  // Contains the main() for running the tests
platformio.ini      // PlatformIO project configuration file. Defines environments, platforms, build flags, e.t.c

The PlatformIO Config File

Data not specific to any one environment goes under the [platformio] section in the platformio.ini file.

Want to use a private package for a particular project? The good news is that PlatformIO supports SSH-style Git URLs and will use your default SSH key to attempt to git clone the package. You can specify a URL to a private package repo in platformio.ini with the following line:

platform_packages = framework-arduino-samd-privatepackage @

A specific branch or tag can be specified by appending a # and then the name of the branch/tag (note that # denotes the start of a comment in an INI file, but this tag name is processed by the parser…it feels a little strange to be doing this):

platform_packages = framework-arduino-samd-privatepackage @

Enabling Floating-Point printf() Support When Using The mbed Platform

If you are trying to print a floating point number using printf() (or other functions in the same family such as snprintf()) like so:

printf("%f\n", 2.3);

but are just getting the string %f, it could be because floating-point printf() support is disabled. To enable it, create a file (if it doesn’t already exist) called mbed_app.json in the root directory of your PlatformIO project, and add the following lines:

    "target_overrides": {
      "*": {
        "platform.minimal-printf-enable-floating-point": true

The native Build Environment

Note that none of the standard header files you rely on (<Arduino.h>, <mbed.h>) will be available when compiling for your native host. You will have to “stub” any functions/types that are platform specific before compilation will be successful.

In platformio.ini:

platform = native

Installtion On Windows

When trying to compile on Windows you may get the following error:

'g++' is not recognized as an internal or external command,

PlatformIO does not install gcc or g++ executables for you autmatically, you have to provide them yourself. One way to do this on Windows is to install MinGW:

  1. Download MinGW from
  2. Install MinGW using the following settings:
    • Architecture: x86_64
    • Thread model: posix
  3. Add the bin directory of the MinGW installation to your system PATH. When I installed it the path to the bin directory was C:\Program Files\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin.


PlatformIO supports unit testing both on real hardware and on native (host) machines. It also supports testing via remote connection (e.g. the internet) to another device which has the target hardware connected to it (which is suitable for cloud-based CICD and cloud-based IDE development).

To write some unit tests, first create a test_main.cpp in the test/ directory of your PlatformIO project. Then include <unity.h>. Testing is started with UNITY_BEGIN() and finished with UNITY_END():

#include <unity.h>

int main() {
    // Test functions goes here

RUN_TEST() takes in a function pointer to the test you want to run. It accepts a C-style function pointer, so one unfortunate limiation is you cannot pass in member functions. The best workaround for this is to not use classes to define your test suite.

Output of pio test (with one test intentionally failing for demonstration purposes):

PS C:\Users\gbmhunter\pio-test> pio test
Verbose mode can be enabled via `-v, --verbose` option
Collected 1 items

Processing * in testing environment
If you don't see any output for the first 10 secs, please reset board (press reset button)

test\test_main.cpp:17:test_led_builtin_pin_number:FAIL: Expected 13 Was 32      [FAILED]
test\test_main.cpp:85:test_led_state_high       [PASSED]
test\test_main.cpp:87:test_led_state_low        [PASSED]
test\test_main.cpp:85:test_led_state_high       [PASSED]
test\test_main.cpp:87:test_led_state_low        [PASSED]
test\test_main.cpp:85:test_led_state_high       [PASSED]
test\test_main.cpp:87:test_led_state_low        [PASSED]
test\test_main.cpp:85:test_led_state_high       [PASSED]
test\test_main.cpp:87:test_led_state_low        [PASSED]
test\test_main.cpp:85:test_led_state_high       [PASSED]
test\test_main.cpp:87:test_led_state_low        [PASSED]
11 Tests 1 Failures 0 Ignored
=========================================================================================== [FAILED] Took 14.40 seconds ===========================================================================================
Test    Environment    Status    Duration
------  -------------  --------  ------------
*       testing        FAILED    00:00:14.400
====================================================================================== 1 failed, 0 succeeded in 00:00:14.400 ======================================================================================

Building The Code In The src/ Directory

To build the code in src/ when pio test is run, add test_build_project_src = true to the environment in your file, e.g.:

platform = ...
test_build_project_src = true



Related Content:


comments powered by Disqus