Firmware libraries

Overview

Libraries are a central part of project development on the Particle platform leveraged by thousands of engineers in our community. Simply stated, a Particle library is a collection of reusable firmware code that can be easily added to one or many Particle projects.

Leveraging high quality libraries to build Internet-connected projects and applications can significantly reduce the risk, time, and cost associated with creating IoT product or device. Libraries also make it possible to easily maintain and reuse common code blocks, as well as incorporate and leverage existing third party libraries from the Particle ecosystem.

Most Arduino libraries are compatible with Particle. We've worked hard to ensure that our firmware API contains all of the most commonly used Arduino functions and firmware commands so that many Arduino libraries can be submitted into the Particle library ecosystem without modification or minimal modification. All of the most popular Arduino libraries are already available through our libraries system, and many others can be easily modified for compatibility.

Particle libraries can include and depend on other Particle libraries. If your library requires another external library as a dependency, it is easy to specify the particular library and even version of the library that your library depends on. A good example is our internet-button library, which depends on the popular neopixel library for controlling NeoPixel LEDs. You can learn more about libraries with dependencies in the Library file structure section below.

Search and browse libraries

Kinds of libraries

Public libraries

The vast majority of Particle libraries are developed and maintained by the Particle community and made available for broader use via the Particle libraries ecosystem. All public libraries are available for public consumption through our development tools and via our Libraries API. The availability of such a large number of libraries in a single place makes developing IoT products on the Particle platform fast and simple.

Note that a library may have its own associated open source license that limits or restricts redistribution or commercialization of the library.

Official libraries

Official libraries are libraries that were created by members of the Particle team and are designed to be used with Particle hardware.

All Particle libraries meet the same quality standards as Verified libraries, and appear in the library list with the Particle logo next to them.

Verified libraries

Verified libraries are community-contributed libraries that have been reviewed and confirmed by members of the Particle team to meet the following criteria:

The library is well documented. It contains in-line comments that document proper usage of the library and contains example applications that demonstrate how to use each of the included functions.
The library has been reviewed for quality. The library compiles on all relevant hardware platforms and performs as intended. The library includes testing instructions (verification.txt) that anyone can follow to independently verify that the library is working as expected.
The library has improved visibility. Verified libraries float to the top of library searches, improving the visibility of the library within the Particle ecosystem.

Private libraries

Private libraries are libraries that have been uploaded to the Particle Device Cloud for reuse with many projects, but are only visible to the individual who created and submitted the library. Private libraries can be published as public libraries at any time by the author of the library using the particle library publish command.

Workbench and CLI pseudo-libraries

If you are using Particle Workbench or the Particle CLI, you may also want to store shared code across firmware or products using pseuo-libraries in a source code control system like Github.

This allows private sharing of code between multiple users (unlike private libraries), along with robust change logging and version control.

This technique is not available in the Web IDE, however we also do not recommend the Web IDE for product development.

See Workbench pseudo-libraries, below, for more information.

Library file structure

Overview

Every Particle library complies with the following file structure that will be automatically generated when a new library is initialized:

MyLibrary/
  examples/
    usage/
      usage.ino
  src/
    MyLibrary.cpp
    MyLibrary.h
  library.properties
  README.md
  LICENSE

examples is the folder that contains the example applications that reference your library with one example per directory. If your library controls LEDs, for example, you should include an example called examples/control/control.ino that demonstrates how someone could use the library in a typical application.

src is the folder that contains the actual library files (.cpp and .h files) that define the library's behavior. Everything in the src folder will be compiled when a user adds the library to their project and compiles it. You can add subfolders to src if you have many files in your library.

library.properties includes descriptive information about your library (title, description, version, author, license), and also specifies any other libraries that your library depends on. Libraries dependencies can be tagged at a particular version in this file.

README.md provides instructions for library creators on creation and usage.

LICENSE or LICENSE.txt is the file that defines the license that the public library is distributed with. All libraries in Particle's library ecosystem must include an associated license.

library.properties fields

name Name of the library. The name must be unique, so there aren't 2 libraries with the same name. It will be the name of the directory as well as the name of main .cpp and .h file. Note that library names must be unique across both public and private libraries. Thus you can get an error uploading a library whose name you cannot see in the community libraries because someone else has created a private library with that name already.
version A Semantic Versioning version number like 1.0.0
author Your name and email like The Author <author@example.com>. If there are several authors, separate them with commas.
license The acronym for the license this library is released under, such as GPL, MIT, Apache-2.
sentence A one sentence description of the library that will be shown in the library browser.
paragraph A longer description to be shown in the details page of the library. This is always shown after sentence so start with the second sentence of the description.
url The web page that a user wanting more information would visit like a GitHub URL.
repository The git repository like http://github.com/user/project.git, if available.
architectures A comma-separated list of supported hardware boards that are compatible with your library. If missing or set to *, the library will be available for all architectures.
dependencies. Other library that this library depends on, one line per library dependency. The value is the desired version number of the library dependency.
whitelist Additional files to include when publishing a library. By default these files are included in a library when publishing: *.ino, *.pde, *.cpp, *.c, *.c++, *.h, *.h++, *.hpp, *.ipp, *.properties, *.md, *.txt, *.S, *.a and LICENSE.

Project file structure

The extended structure expands on the simple structure, placing all application sources in the src folder.

myapp/
  project.properties
  src/
    myapp.cpp

An extended project has full support for libraries, supporting both library add and copied libraries.

An extended project can be created by using the CLI particle project create command.

Your main application file can be a .cpp or a .ino file.

Projects with pseudo-libraries

It's also possible to include library-like files in the lib directory. See Workbench pseudo-libraries, below, for more information.

myapp/
  project.properties
  src/
    myapp.cpp
  lib/
    library1/
      src/
        library1.cpp
    SharedCode/
      src/
        SharedCode.cpp

particle.include and particle.ignore

The particle.include and particle.ignore files provide a way to include or exclude additional files from the cloud compiler. Please note that these files are only for special extras and the default files like the source and header files are handled separately and are not affected by the patterns specified in these two files. The include and ignore files can be located either in the project's root directory or in any of its subdirectories.

When the particle.include file is placed in the root directory, files matching the specified patterns are searched recursively from the root directory. On the other hand, if the particle.include file is placed in a subdirectory, the search for matching files is performed recursively starting from that subdirectory as the base. The system automatically handles duplicates, so there is no need to worry about them.

Similarly, the particle.ignore file follows the same behavior, but instead of including files, it excludes files that match the specified patterns from being sent to the cloud compiler.

Example particle.include file that includes all .def files:

**/*.def

Example particle.ignore file to not upload the test and docs directories in a library.

test/**
docs/**

Asset OTA

Particle Workbench and the Particle CLI will automatically generated bundled assets when the project.properties file contains an assetOtaFolder key and a value containing a valid directory.

assetOtaFolder=assets

For example:

myapp/
  project.properties
  src/
    myapp.cpp
  assets/
    coprocessor.bin

Older file structures

These file structures are currently still supported, but may be deprecated in the future. We recommend using the structure above, with the src directory and a project.properties file, for all projects.

Show older file structures

Legacy structure

The legacy project structure stores files in the root of the project. There is no project definition file. This is the structure used by all projects prior to libraries v2.

myapp/
  application.ino

A legacy project does not support using libraries.

Simple structure

The simple project structure is similar to the legacy structure - the project sources are stored in the root. However, the project also includes a project definition file project.properties. Even saving a blank project.properties file is enough to make a simple project.

myapp/
  myapp.ino
  project.properties

A simple project has standard support for libraries; libraries can be added to the project via the CLI library add command.

Using libraries

Libraries consumption is supported in each of our three primary development tools. Instructions for using libraries can be found in the documentation for each of those tools, linked below:

Contributing libraries

The main steps for contributing a library are preparing the structure, writing the code, testing the examples, uploading a private version and publishing to the public.

Library contribution is currently supported via our Command Line Interface (CLI).

Contributing libraries with the Command Line Interface (CLI)

Preparing the structure

There are several ways to start contributing a Particle library.

You can start a brand new library by generating the file structure with the Command Line Interface (CLI) using the particle library create or downloading the example library and editing it.

If you made a library in the past, you can migrate it to the new format with particle library migrate.

You can modify an existing library by forking the code from GitHub. You can also download an existing library through the CLI with particle library view <library_name>. Make sure you move the library to a new folder before modifying it in that case.

You can also start with an existing Arduino library from GitHub. Particle libraries have the same structure as Arduino libraries.

Writing the code

The main sources of the library go into src/lib_name.cpp and src/lib_name.h. More complex libraries may use a nested structure within the src/ directory. For example src/subFolder/subhHeader.h and referenced as #include <subFolder/subHeader.h>.

Create at least one example .ino file inside a subfolder of examples to show people how to use the library.

If your library depends on other libraries you can add those dependencies to library.properties with particle library add. For example, since the Internet Button contains NeoPixel LEDs, the InternetButton library has the line dependencies.neopixel=0.0.10 in library.properties to indicate this.

List the hardware platforms supported by your library supports to the architectures field in library.properties, or use * for all current platforms.

Review the library.properties and README.md and fill in as much information as possible.

If you wish to develop libraries using Particle Workbench, see Developing Particle Libraries with Workbench.

Testing the examples

The best way to ensure people will use your library is to provide good examples.

Once you've written the first draft of the library you can test the examples on hardware you own in the CLI with particle flash <my_device> examples/<example_name> from the library folder.

Uploading a private version

Once your library is ready to go, you can upload it to Particle in the CLI with particle library upload from the library folder.

When you upload a new private version you can use the library as usual from your own account in the Web IDE, Particle Workbench, or CLI.

If you find issues, you can upload another private version with the same version number.

When you want to modify an existing library for your own projects only, you can stop after uploading a private version. However if you want other people to be able to use the library go on to publishing it.

Publish to the public

When a version is ready for prime time, simply type particle library publish <my_lib> in the CLI and it will make the latest private version available to the public.

After this, anybody with a Particle account will be able to use your library! Thank you!

Migrating libraries

On January 23, 2017, Particle introduced a new version of our firmware library manager, requiring that libraries be migrated from the old library structure (v1) to our new library structure (v2).

With our original firmware library manager, libraries could only be contributed and consumed through our Web IDE. We’ve now upgraded the library manager behind the Web IDE, and made those libraries accessible in Particle Workbench and the Particle CLI.

Libraries under the new library format have the following features:

Every library now has a library.properties file that can be used to specify external library dependencies, library version number, description, and associated open-source license
Libraries are now accessible via our firmware libraries API
Libraries can now be added to projects in Particle Workbench and the Particle CLI

All existing Particle applications that included a v1 library have been preserved and will continue to function as before. However, all new library includes will pull from our migrated v2 library list, so all new Particle projects that include a library will use the updated library structure.

For that reason, it may be necessary to migrate a library to the new library structure if the library was originally created as a v1 library.

Instructions for migrating v1 libraries to the new library format using the Particle CLI are included below.

Using the CLI

Follow these steps to migrate a v1 Particle library to the new v2 structure using the Particle CLI:

Install the Particle CLI version 1.19 or later.
- If you do not have the Particle CLI installed on your machine, you can download and install it using our OS-specific instructions, here
- If you already have the Particle CLI installed, you can update it to the latest version by running npm update -g particle-cli
Run particle library migrate in your library directory
Edit the newly created library.properties file to add a GitHub URL to the url field (like https://github.com/particle-iot/internetbutton) and the git remote to the repository field (like https://github.com/particle-iot/internetbutton.git)
If your library depends on another library, run particle library add dependency in your library directory and remove the source files of the other library from your own repository
Ensure that the example applications for your library compile by running particle compile photon examples/<name> in your library directory
Refresh the README.md file for your library with detailed information and instructions for using and interacting with the library. The README.md file will be used as the "home page" for your library.
- See https://github.com/particle-iot/PowerShield for a good example.
Upload a private version of your library by running particle library upload
Try adding the library to a project using the Web IDE
Publish the new public version of the library by running particle library publish MyLibrary in the CLI
Push to GitHub, and go celebrate!

Common issues with porting libraries

If you have a library MyLibrary be sure to have the file src/MyLibrary.h. This should exist, even if it only includes other header files. The Web IDE will automatically add #include "MyLibrary.h" to the project .ino file when adding the library.
When uploading a new version of a library, all files in the library directory are uploaded. Be careful in case you have files in there you don’t want to upload like test binaries and large PDFs.
You can upload a private version multiple times with the same version number, but once you publish a version to the public you won’t be able to upload with the same version number. If you make a small mistake just increase the version number and upload again.
When porting a library, the library itself must have the source in the src directory. If it has files in the top level of the library project, they must be moved into a new src directory.
When porting a library, the name field in library.properties must match the directory name. This is not enforced on Arduino, so some libraries have a different name here.
You cannot set #define variables outside the project, such as using a -D in a Makefile. These external defines will need to be moved into header file instead.
You also cannot set an alternate search path in a library (equivalent to a -I in a Makefile). However, the src directory is added recursively, so any files within src will be found during compilation.
It is not possible to include a pre-compiled binary library (.a or .so) within a Particle library.
Beware of libraries that contain code for other non-Particle hardware platforms. This code can be picked up in the published library and, if large, can cause a timeout while attempting to compile the library, if not an error.
If you are porting code that you want to contribute back upstream, you can surround Particle-specific code with #ifdef PARTICLE.
If you need to modify a public library for private modifications or to fix a bug, see also Workbench pseudo-libraries, below.
Beware of libraries with LGPL licensing. Due to the way the Particle libraries system works, statically linking the library to the application, the library exception in LGPL licensing does not apply! This means that LGPL (or GPL) licensed libraries cannot be used in closed-source commercial projects.

If you're having additional issues with library migration or contribution, please feel free to post a message in the community forums.

Workbench pseudo-libraries

Using source control

We highly recommend using a source code control system like Github to manage your projects. This assures that you can see all of the changes made over history, who made them, and also provide secure sharing of code. Github provides private repositories in the free plan; Github private repositories can also grant access to a specific list of Github users.

You will generally commit your entire project, with the following notes:

target/ should not be committed, as it contains built binaries and is very large. Include it in your .gitignore file.
.vscode/ is normally committed as it contains project settings, but in some cases you may want to commit the base settings once and avoid updating it so your team members won't have any of their private settings overwritten in the future.

This technique can also be used to share a complete project publicly, by making your Github repository public.

Working with public libraries

When you add a library in Workbench using Particle: Install Library it does two things:

Adds to project.properties as a dependency.
Copies the library source into the lib/ directory at the top of your project.

The local copy in the lib directory is used when you compile locally. However, if you remove the dependency from project.properties, then the local copy will also be used for cloud compiles.

We recommend that you:

Include the public library source in your project lib directory and store it in source control like Github.
Remove the dependency entry from project.properties so the behavior will be consistent between local and cloud compiles.

Modifying public libraries

Sometimes you will need to make a small modification to a public library to make it suit your needs, or fix a minor compilation error caused in a new version of the compiler or Device OS. This is easy to do with pseudo-libraries.

Install the library using Particle: Install Library
Remove the dependency entry for the library from project.properties

Now you are free to make modifications to the library in the lib directory and these changes will used for local, cloud, and CLI cloud compiles.

Using a 3rd-party library not in the community libraries

Sometimes you will encounter a library that is available in Github, but not in the Particle libraries system. In this case, download or clone the repo into the lib directory of your project.

Make sure all of the .cpp and .h files are in a src directory; they cannot be in the top level of the library directory within lib or in other directories.

Firmware libraries

Overview

Kinds of libraries

Public libraries

Official libraries

Verified libraries

Private libraries

Workbench and CLI pseudo-libraries

Library file structure

Overview

library.properties fields

Project file structure

Projects with pseudo-libraries

particle.include and particle.ignore

Asset OTA

Older file structures

Using libraries

Contributing libraries

Preparing the structure

Writing the code

Testing the examples

Uploading a private version

Publish to the public

Migrating libraries

Using the CLI

Common issues with porting libraries

Workbench pseudo-libraries

Using source control

Working with public libraries

Modifying public libraries

Using a 3rd-party library not in the community libraries

Sharing code