library.json

library.json is a manifest file of a library package. It allows developers to keep a project in its own structure and define:

  • compatible frameworks and platforms
  • external dependencies
  • advanced build settings.

A data in library.json should be represented in JSON-style via associative array (name/value pairs). An order doesn’t matter. The allowable fields (names from pairs) are described below.

You can validate library.json manifest file using pio package pack command.

name

Required | Type: String | Max. Length: 50

A name of a library.

  • Must be unique
  • Should be slug style for simplicity, consistency, and compatibility. Example: HelloWorld
  • Can contain a-z, digits, and dashes (but not start/end with them)
  • Consecutive dashes and [:;/,@<>] chars are not allowed.

version

Required | Type: String | Max. Length: 20

A version of a current library source code. Can contain a-z, digits, dots or dash and should be Semantic Versioning compatible.

Example:

"name": "Bar",
"version": "1.0.0",
"repository":
{
    "type": "git",
    "url": "https://github.com/foo/bar.git"
}

description

Required | Type: String | Max. Length: 255

The field helps users to identify and search for your library with a brief description. Describe the hardware devices (sensors, boards and etc.) which are suitable with it.

keywords

Required | Type: String or Array | Max. Length: 255

Used for search by keyword. Helps to make your library easier to discover without people needing to know its name.

The keyword should be lowercased, can contain a-z, digits and dash (but not start/end with them). A list from the keywords can be specified with separator , or declared as Array.

repository

Optional | Type: Object

The repository in which the source code can be found. The field consists of the next items:

  • type the only “git”, “hg” or “svn” are supported
  • url
  • branch if is not specified, default branch will be used. This field will be ignored if tag/release exists with the value of version.

Example:

"repository":
{
    "type": "git",
    "url": "https://github.com/foo/bar.git"
}

authors

Optional | Type: Object or Array

An author contact information

  • name Full name (Required)
  • email
  • url An author’s contact page
  • maintainer Specify “maintainer” status

Examples:

"authors":
{
    "name": "John Smith",
    "email": "me@john-smith.com",
    "url": "https://www.john-smith/contact"
}

...

"authors":
[
    {
        "name": "John Smith",
        "email": "me@john-smith.com",
        "url": "https://www.john-smith/contact"
    },
    {
        "name": "Andrew Smith",
        "email": "me@andrew-smith.com",
        "url": "https://www.andrew-smith/contact",
        "maintainer": true
    }
]

Note

If authors field is not defined, PlatformIO will try to fetch data from VCS provider (Github, Gitlab, etc) if repository is declared.

license

Optional | Type: String

A SPDX license ID of the library. You can check the full list of SPDX license IDs (see “Identifier” column).

"license": "Apache-2.0"

homepage

Optional | Type: String | Max. Length: 255

Home page of a library (if is different from repository url).

export

Optional | Type: Object

This option is useful if you need to exclude extra data (test code, docs, images, PDFs, etc). It allows one to reduce the size of the final archive.

To check which files will be included in the final packages, please use pio package pack command.

Possible options:

include

Optional | Type: Array | Glob Pattern

Export only files that matched declared patterns.

Pattern Meaning

Pattern Meaning
* matches everything
? matches any single character
[seq] matches any character in seq
[!seq] matches any character not in seq

Example:

"export": {
    "include":
    [
        "dir/*.[ch]pp",
        "dir/examples/*",
        "*/*/*.h"
    ]
}

exclude

Optional | Type: Array | Glob Pattern

Exclude the directories and files which match with exclude patterns.

frameworks

Optional | Type: String or Array

A list with compatible frameworks. The available framework names are defined in the Frameworks section.

Example:

"frameworks": ["espidf", "freertos"]

If the library is compatible with the all frameworks, then do not declare this field or you use * symbol:

"frameworks": "*"

platforms

Optional | Type: String or Array

A list with compatible development platforms. The available platform name are defined in Development Platforms section.

Example:

"frameworks": ["atmelavr", "espressif8266"]

If the library is compatible with the all platforms, then do not declare this field or use * symbol:

"platforms": "*"

dependencies

Optional | Type: Array or Object

A list of dependent libraries. They will be installed automatically with pio lib install command.

Allowed requirements for dependent library:

  • owner | Type: String – an owner name (username) from the PlatformIO Registry
  • name | Type: String – library name
  • version | Type: String – version or version range in SemVer format
  • frameworks | Type: String or Array – project compatible Frameworks
  • platforms | Type: String or Array – project compatible Development Platforms

The version supports Semantic Versioning ( <major>.<minor>.<patch>) and can take any of the following forms:

  • 1.2.3 - an exact version number. Use only this exact version
  • ^1.2.3 - any compatible version (exact version for 1.x.x versions
  • ~1.2.3 - any version with the same major and minor versions, and an equal or greater patch version
  • >1.2.3 - any version greater than 1.2.3. >=, <, and <= are also possible
  • >0.1.0,!=0.2.0,<0.3.0 - any version greater than 0.1.0, not equal to 0.2.0 and less than 0.3.0

The rest possible values including VCS repository URLs are documented in pio lib install command.

Example:

"dependencies":
[
    {
        "owner": "bblanchon",
        "name": "ArduinoJson",
        "version": "^6.16.1"
    },
    {
        "owner": "me-no-dev",
        "name": "AsyncTCP",
        "version": "*",
        "platforms": ["espressif32"]
    },
    {
        "name": "external-repo",
        "version": "https://github.com/user/package.git#1.2.3"
    },
    {
        "name": "external-zip",
        "version": "https://github.com/me-no-dev/AsyncTCP/archive/master.zip"
    }
]

A short definition of dependencies is allowed:

"dependencies":
{
    "bblanchon/ArduinoJson": "^6.16.1",
    "me-no-dev/AsyncTCP": "*",
    "external-repo": "https://github.com/user/package.git#1.2.3",
    "external-zip": "https://github.com/me-no-dev/AsyncTCP/archive/master.zip"
}

examples

Optional | Type: Array | Glob Pattern

A list of example patterns. This field is predefined with default value:

"examples": [
    {
        "name": "Hello",
        "base": "examples/world",
        "files": [
            "platformio.ini",
            "include/world.h",
            "src/world.c",
            "README",
            "extra.py"
        ]
    },
    {
        "name": "Blink",
        "base": "examples/blink",
        "files": ["blink.cpp", "blink.h"]
    }
]

build

Optional | Type: Object

Specify advanced settings, options and flags for the build system. Possible options:

flags

Optional | Type: String or Array

Extra flags to control preprocessing, compilation, assembly and linking processes. More details build_flags.

unflags

Optional | Type: String or Array

Remove base/initial flags which were set by development platform. More details build_unflags.

includeDir

Optional | Type: String

Custom location of library header files. A default value is include and means that folder is located in the root of a library.

srcDir

Optional | Type: String

Custom location of library source code. A default value is src and means that folder is located in the root of a library.

srcFilter

Optional | Type: String or Array

Specify which source files should be included/excluded from build process. The path in filter should be relative to the srcDir option of a library.

See syntax in src_filter.

Please note that you can generate source filter “on-the-fly” using extraScript (see below)

extraScript

Optional | Type: String

Launch extra script before build process. More details extra_scripts.

Example (HAL-based library)

This example demonstrates how to build HAL-dependent source files and exclude other source files from a build process.

Project structure

├── lib
│   ├── README
│   └── SomeLib
│       ├── extra_script.py
│       ├── hal
│       │   ├── bar
│       │   │   ├── hal.c
│       │   │   └── hal.h
│       │   ├── foo
│       │       ├── hal.c
│       │       └── hal.h
│       ├── library.json
│       ├── SomeLib.c
│       └── SomeLib.h
├── platformio.ini
└── src
    └── test.c

platformio.ini

[env:foo]
platform = native
build_flags = -DHAL=foo

[env:bar]
platform = native
build_flags = -DHAL=bar

library.json

{
    "name": "SomeLib",
    "version": "0.0.0",
    "build": {
        "extraScript": "extra_script.py"
    }
}

extra_script.py

Import('env')
from os.path import join, realpath

# private library flags
for item in env.get("CPPDEFINES", []):
    if isinstance(item, tuple) and item[0] == "HAL":
        env.Append(CPPPATH=[realpath(join("hal", item[1]))])
        env.Replace(SRC_FILTER=["+<*>", "-<hal>", "+<%s>" % join("hal", item[1])])
        break

# pass flags to a global build environment (for all libraries, etc)
global_env = DefaultEnvironment()
global_env.Append(
    CPPDEFINES=[
        ("MQTT_MAX_PACKET_SIZE", 512),
        "ARDUINOJSON_ENABLE_STD_STRING",
        ("BUFFER_LENGTH", 32)
    ]
)

libArchive

Optional | Type: Boolean

Create an archive (*.a, static library) from the object files and link it into a firmware (program). This is default behavior of PlatformIO Build System ("libArchive": true).

Setting "libArchive": false will instruct PlatformIO Build System to link object files directly (in-line). This could be useful if you need to override weak symbols defined in framework or other libraries.

You can disable library archiving globally using lib_archive option in “platformio.ini” (Project Configuration File).

libLDFMode

Optional | Type: String

Specify Library Dependency Finder Mode. See Dependency Finder Mode for details.

libCompatMode

Optional | Type: String

Specify Library Compatibility Mode. See Compatibility Mode for details.

Examples

  1. Custom macros/defines
"build": {
    "flags": "-D MYLIB_REV=1.2.3 -DRELEASE"
}
  1. Extra includes for C preprocessor
"build": {
    "flags": [
        "-I inc",
        "-I inc/target_x13"
    ]
}
  1. Force to use C99 standard instead of C11
"build": {
    "unflags": "-std=gnu++11",
    "flags": "-std=c99"
}
  1. Build source files (c, cpp, h) at the top level of the library
"build": {
    "srcFilter": [
        "+<*.c>",
        "+<*.cpp>",
        "+<*.h>"
    ]
}
  1. Extend PlatformIO Build System with own extra script
"build": {
    "extraScript": "generate_headers.py"
}

generate_headers.py

Import('env')
# print(env.Dump())
env.Append(
    CPPDEFINES=["HELLO=WORLD", "TAG=1.2.3", "DEBUG"],
    CPPPATH=["inc", "inc/devices"]
)

# some python code that generates header files "on-the-fly"