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Customizing the Build

Table of contents

Rust configuration flags

The following are flags passed to rustc that influence the build.

  • --cfg espidf_time64

    This is a flag for the libc crate that uses 64-bits (instead of 32-bits) for time_t. This must be set for ESP-IDF 5.0 and above and must be unset for lesser versions.

  • -Zbuild-std=std,panic_abort

    Required for std support. Rust does not provide std libraries for ESP32 targets since they are tier-2/-3.

Features

  • native

    This is the default feature for downloading all tools and building the ESP-IDF framework using the framework's "native" (own) tooling. It relies on build and installation utilities available in the embuild crate.

    The native builder installs all needed tools to compile this crate as well as the ESP-IDF framework itself.

  • pio

    This is a backup feature for installing all build tools and building the ESP-IDF framework. It uses PlatformIO via the embuild crate.

    Similarly to the native builder, the pio builder also automatically installs all needed tools (PlatformIO packages and frameworks in this case) to compile this crate as well as the ESP-IDF framework itself.

    [!WARNING] The pio builder is less flexible than the default native builder in that it can work with only one, specific version of ESP-IDF. At the time of writing, this is V4.3.2.

  • binstart

    Defines the esp-idf entry-point for when the root crate is a binary crate that defines a main function.

  • libstart

    Defines the esp-idf entry-point for when the root crate is a library crate. the root crate is expected to provide a

    #[no_mangle]
fn main() {}

    function.

sdkconfig

The esp-idf makes use of an sdkconfig file for its compile-time component configuration (see the esp-idf docs for more information). This config is separate from the build configuration.

(native builder only) Using cargo-idf to interactively modify ESP-IDF's sdkconfig file

TBD: Upcoming

(pio builder only) Using cargo-pio to interactively modify ESP-IDF's sdkconfig file

To enable Bluetooth, or do other configurations to the ESP-IDF sdkconfig you might take advantage of the cargo-pio Cargo subcommand:

  • To install it, issue cargo install cargo-pio --git https://github.com/ivmarkov/cargo-pio
  • To open the ESP-IDF interactive menuconfig system, issue cargo pio espidf menuconfig in the root of your binary crate project
  • To use the generated/updated sdkconfig file, follow the steps described in the "Bluetooth Support" section

ESP-IDF configuration

There are two ways to configure how the ESP-IDF framework is compiled:

  1. Environment variables, denoted by $VARIABLE;

    The environment variables can be passed on the command line, or put into the [env] section of a .cargo/config.toml file (see cargo reference).

  2. The [package.metadata.esp-idf-sys] section of the Cargo.toml, denoted by field.

    [!NOTE] Configuration can only come from the root crate's Cargo.toml. The root crate is the package in the workspace directory. If there is no root crate in case of a virtual workspace, its name can be specified with the ESP_IDF_SYS_ROOT_CRATE environment variable.

    [!WARNING] Environment variables always take precedence over Cargo.toml metadata.

Note

workspace directory

The workspace directory mentioned here is always the directory containing the Cargo.lock file and the target directory (unless configured otherwise, see the note below about CARGO_TARGET_DIR) where the build artifacts are stored. It can be overridden with the CARGO_WORKSPACE_DIR environment variable, should this not be the right directory.
(See embuild::cargo::workspace_dir for more information).

There is no need to explicitly add a [workspace] section to the Cargo.toml of the workspace directory.

Please note that if you have set CARGO_TARGET_DIR and moved your target directory out of the crate root, then embuild is not able to locate the crate root. This will result in it among other things ignoring your local sdkconfig.defaults. In this case you must declare:

[env]
CARGO_WORKSPACE_DIR = { value = "", relative = true }

in the .cargo/config.toml file, to force it to look in the current directory.

The following configuration options are available:

  • esp_idf_sdkconfig_defaults, $ESP_IDF_SDKCONFIG_DEFAULTS

    A single path or a list of paths to sdkconfig.defaults files to be used as base values for the sdkconfig. If such a path is relative, it will be relative to the workspace directory.

    Defaults to sdkconfig.defaults.

    In case of the environment variable, multiple elements should be ;-separated.

    [!NOTE] For each defaults file in this list, a more specific file will also be searched and used. This happens with the following patterns and order (least to most specific):

    1. <path>
    2. <path>.<profile>
    3. <path>.<mcu>
    4. <path>.<profile>.<mcu>

    where <profile> is the current cargo profile used (debug/release) and <mcu> specifies the mcu for which this is currently compiled for (see the mcu configuration option below).

    [!WARNING] A setting contained in a more specific defaults file will override the same setting specified in a less specific one. For example, in a debug build, flags in sdkconfig.debug override those in sdkconfig.defaults.

  • esp_idf_sdkconfig, $ESP_IDF_SDKCONFIG

    The sdkconfig file used to configure the esp-idf. If this is a relative path, it is relative to the workspace directory.

    Defaults to sdkconfig.

    [!NOTE] Similar to the sdkconfig.defaults-file a more specific sdkconfig-file will be selected if available. This happens with the following patterns and precedence:

    1. <path>.<profile>.<mcu>
    2. <path>.<mcu>
    3. <path>.<profile>
    4. <path>

     

    [!NOTE] native builder only:
    The cargo optimization options (debug and opt-level) are used by default to determine the compiler optimizations of the esp-idf, however if the compiler optimization options are already set in the sdkconfig they will be used instead.

  • esp_idf_tools_install_dir, $ESP_IDF_TOOLS_INSTALL_DIR

    The install location for the ESP-IDF framework tooling.

    [!NOTE] The framework tooling is either PlatformIO when the pio builder is used, or the ESP-IDF native toolset when the native builder is used (default).

    This option can take one of the following values:

    • workspace (default) - the tooling will be installed or used in <crate-workspace-dir>/.embuild/platformio for pio, and <crate-workspace-dir>/.embuild/espressif for the native builder;

    • out - the tooling will be installed or used inside esp-idf-sys's build output directory, and will be deleted when cargo clean is invoked;

    • global - the tooling will be installed or used in its standard directory (~/.platformio for PlatformIO, and ~/.espressif for the native ESP-IDF toolset);

    • custom:<dir> - the tooling will be installed or used in the directory specified by <dir>. If this directory is a relative location, it is assumed to be relative to the workspace directory;

    • fromenv - use the build framework from the environment

      • native builder: use activated esp-idf environment (see esp-idf docs unix / windows)
      • pio builder: use platformio from the environment (i.e. $PATH)

      and error if this is not possible.

    [!WARNING] Please be extra careful with the custom:<dir> setting when switching from pio to native and the other way around, because the builder will install the tooling in <dir> without using any additional platformio or espressif subdirectories, so if you are not careful, you might end up with both PlatformIO, as well as the ESP-IDF native tooling intermingled together in a single folder.

    [!WARNING] The ESP-IDF git repository will be cloned inside the tooling directory. The native builder will use the esp-idf at idf_path if available.

  • idf_path, $IDF_PATH (native builder only)

    A path to a user-provided local clone of the esp-idf, that will be used instead of the one downloaded by the build script.

  • esp_idf_version, $ESP_IDF_VERSION (native builder only)

    The version used for the esp-idf, can be one of the following:

    • commit:<hash>: Uses the commit <hash> of the esp-idf repository. Note that this will clone the whole esp-idf not just one commit.
    • tag:<tag>: Uses the tag <tag> of the esp-idf repository.
    • branch:<branch>: Uses the branch <branch> of the esp-idf repository.
    • v<major>.<minor> or <major>.<minor>: Uses the tag v<major>.<minor> of the esp-idf repository.
    • <branch>: Uses the branch <branch> of the esp-idf repository.

    Defaults to v4.4.1.

  • esp_idf_repository, $ESP_IDF_REPOSITORY (native builder only)

    The URL to the git repository of the esp-idf, defaults to https://github.com/espressif/esp-idf.git.

    [!NOTE] When the pio builder is used, it is possible to achieve something similar to ESP_IDF_VERSION and ESP_IDF_REPOSITORY by using the platform_packages PlatformIO option as follows:

    ESP_IDF_PIO_CONF="platform_packages = framework-espidf @ <git-url> [@ <git-branch>]"

    The above approach however has the restriction that PlatformIO will always use the ESP-IDF build tooling from its own ESP-IDF distribution, so the user-provided ESP-IDF branch may or may not compile. The current PlatformIO tooling is suitable for compiling ESP-IDF branches derived from versions 4.3.X and 4.4.X.

  • $ESP_IDF_GLOB[_XXX]_BASE and $ESP_IDF_GLOB[_XXX]_YYY

    A pair of environment variable prefixes that enable copying files and directory trees that match a certain glob mask into the native C project used for building the ESP-IDF framework:

    • ESP_IDF_GLOB[_XXX]_BASE specifies the base directory which will be glob-ed for resources to be copied

    • ESP_IDF_GLOB[_XXX]_BASE_YYY specifies one or more environment variables that represent the glob masks of resources to be searched for and copied, using the directory designated by the ESP_IDF_GLOB[_XXX]_BASE environment variable as the root. For example, if the following variables are specified:

      • ESP_IDF_GLOB_HOMEDIR_BASE=/home/someuser
      • ESP_IDF_GLOB_HOMEDIR_FOO=foo*
      • ESP_IDF_GLOB_HOMEDIR_BAR=bar* ... then all files and directories matching 'foo*' or 'bar*' from the home directory of the user will be copied into the ESP-IDF C project.

      Note also that _HOMEDIR in the above example is optional, and is just a mechanism allowing the user to specify more than one base directory and its glob patterns.

  • $ESP_IDF_PIO_CONF_XXX (pio builder only)

    A PlatformIO setting (or multiple settings separated by a newline) that will be passed as-is to the platformio.ini file of the C project that compiles the ESP-IDF.

    Check the PlatformIO documentation for more information as to what settings you can pass via this variable.

    [!NOTE] This is not one variable, but rather a family of variables all starting with ESP_IDF_PIO_CONF_. For example, passing ESP_IDF_PIO_CONF_1 as well as ESP_IDF_PIO_CONF_FOO is valid and all such variables will be honored.

  • esp_idf_cmake_generator, $ESP_IDF_CMAKE_GENERATOR (native builder only)

    The CMake generator to be used when building the ESP-IDF.

    If not specified or set to default, Ninja will be used on all platforms except Linux/aarch64, where (for now) the Unix Makefiles generator will be used, as there are no Ninja builds for that platform provided by Espressif yet.

    Possible values for this environment variable are the names of all command-line generators that CMake supports with spaces and hyphens removed.

  • esp_idf_path_issues, $ESP_IDF_PATH_ISSUES

    What should happen to the build process if the Rust project path does not meet certain criteria (i.e. path too long on Windows or path contains spaces on Linux). Possible values:

    • err (default) - Fail the build
    • warn - Issue a warning but continue the build
    • ignore - Continue the build and do not issue a warning

  • esp_idf_c_env_vars_issues, $ESP_IDF_C_ENV_VARS_ISSUES (non-CMake build only)

    What should happen to the build process if certain environment variables that might fail the ESP IDF C build are detected. Possible values:

    • warnremove (default) - Do not pass these variables to the ESP IDF C build, and issue a build warning
    • remove - Same as above but do not issue a warning
    • err - Fail the build
    • warn - Issue a warning but do not remove the variables and continue the build
    • ignore - Continue the build and do not issue a warning

    The currently detected environment variables that might be problematic are as follows: CC, CXX, CFLAGS, CCFLAGS, CXXFLAGS, CPPFLAGS, LDFLAGS, GCC_EXEC_PREFIX, COMPILER_PATH, C_INCLUDE_PATH, CPLUS_INCLUDE_PATH.

  • esp_idf_espup_clang_symlink, $ESP_IDF_ESPUP_CLANG_SYMLINK

    Background:

    As part of installing the esp Rust toolchain, the espup utility - on Unix-like systems - configures a hidden symlink in its private folder that points to the Clang compiler library that is also distributed with the esp Rust toolchain (and which - just like the esp Rust toolchain itself - does support the xtensa architecture).

    Since esp-idf-sys uses bindgen to generate raw bindings for the C ESP IDF APIs, it needs to have the LIBCLANG_PATH env var configured to point to the CLang library.

    esp-idf-sys does this automatically, by using the symlink provided by espup.

    Following options are available:

    • try (default) - Check if the symlink is available and use it; continue the build expecting a user-defined LIBCLANG_PATH env var otherwise
    • warn - Same as try but report a warning if the symlink is not available
    • err - Fail the build if the symlink is not available or broken
    • ignore - Do not use the symlink at all

  • esp_idf_component_manager, $ESP_IDF_COMPONENT_MANAGER

    Whether the esp-idf component manager should be on or off.

    Can be any of true, y, yes, on for on, and false, n, no, off for off.

    If not specified, it is on by default.

  • mcu, $MCU

    The MCU name (i.e. esp32, esp32s2, esp32s3 esp32c3, esp32c2, esp32h2, esp32c5, esp32c6, esp32p4).

    If not set this will be automatically detected from the cargo target.

    [!WARNING] Older ESP-IDF versions might not support all MCUs from above.

  • esp_idf_components, $ESP_IDF_COMPONENTS (native builder only)

    Note
    The esp-idf is split into components, where one component is essentially a library with its name typically being the name of the containing directory (for more information see the esp-idf build system docs).

    To see which components esp-idf-sys compiled, run the build with the -vv flag (to display build script output), and look for [esp-idf-sys <version>] Built components: ... in the output.

    The (;-separated for the environment variable) list of esp-idf component names that should be built. This list is used to trim the esp-idf build. Any component that is a dependency of a component in this list will also automatically be built.

    Defaults to all components being built.

    [!NOTE]
    Some components must be explicitly enabled in the sdkconfig.
    Extra components must also be added to this list if they are to be built.

Example

An example of the [package.metadata.esp-idf-sys] section of the Cargo.toml.

[package.metadata.esp-idf-sys]
esp_idf_tools_install_dir = "global"
esp_idf_sdkconfig = "sdkconfig"
esp_idf_sdkconfig_defaults = ["sdkconfig.defaults", "sdkconfig.defaults.ble"]
# native builder only
esp_idf_version = "branch:release/v4.4"
esp_idf_components = ["pthread"]

Extra ESP-IDF components

It is possible to let esp-idf-sys compile extra ESP-IDF components and generate bindings for them.

This is possible by adding an object to the package.metadata.esp-idf-sys.extra_components array of the Cargo.toml. esp-idf-sys will honor all such extra components in the root crate's and all direct dependencies' Cargo.toml.

Note

By only specifying the bindings_header field, one can extend the set of esp-idf bindings that were generated from src/include/esp-idf/bindings.h. To do this you need to create a *.h header file in your project source, and reference that in the bindings_header variable. You can then include extra esp-idf header files from there.

An extra component can be specified like this:

[[package.metadata.esp-idf-sys.extra_components]]
# A single path or a list of paths to a component directory or directory 
# containing components.
# 
# Each path can be absolute or relative. Relative paths will be relative to the
# folder containing the defining `Cargo.toml`.
# 
# **This field is optional.** No component will be built if this field is absent, though
# the bindings of the `[Self::bindings_header]` will still be generated.
component_dirs = ["dir1", "dir2"] # or "dir"


# A remote component to be included in the build. For multiple remote components
# consider declaring multiple extra components.
#
# The components will be managed by the esp-idf component manager. Each remote
# component will correspond to an `idf_component.yml` `dependencies` entry.
# See the Remote component section as to what options are available.
#
# **This field is optional.**
remote_component = { ... }

# The path to the C header to generate the bindings with. If this option is absent,
# **no** bindings will be generated.
#
# The path can be absolute or relative. A relative path will be relative to the
# folder containing the defining `Cargo.toml`.
#
# This field is optional.
bindings_header = "bindings.h"

# If this field is present, the component bindings will be generated separately from
# the `esp-idf` bindings and put into their own module inside the `esp-idf-sys` crate.
# Otherwise, if absent, the component bindings will be added to the existing
# `esp-idf` bindings (which are available in the crate root).
#
# To put the bindings into its own module, a separate bindgen instance will generate
# the bindings. Note that this will result in duplicate `esp-idf` bindings if the
# same `esp-idf` headers that were already processed for the `esp-idf` bindings are
# included by the component(s).
#
# This field is optional.
bindings_module = "name"

and is equivalent to

[package.metadata.esp-idf-sys]
extra_components = [
    { component_dirs = [ "dir1", "dir2" ], bindings_header = "bindings.h", bindings_module = "name" }
]

Remote components (idf component registry)

The esp-idf build systems supports remote components managed by the esp-idf component manager. All remote component dependencies can be specified using the extra esp-idf components remote_component field. Every such dependency maps exactly to a dependency entry in the idf_component.yml manifest.

The component manager will resolve all such dependencies, in addition to those of the C esp-idf components, and download them to the managed_components directory in the esp-idf-sys out (build output) directory.

A lock file (components_<chip>.lock) will be generated in the workspace directory if there is at least one such dependency.

See the esp_idf_component_manager options to turn the component manager off.

A remote component can be specified by:

[package.metadata.esp-idf-sys.extra_components.0.remote_component]
# The name of the remote component. Corresponds to a key in the dependencies of
# `idf_component.yml`.
name = "component_name"
# The version of the remote component. Corresponds to the `version` field of the
# `idf_component.yml`.
version = "1.2"
# A git url that contains this remote component. Corresponds to the `git`
# field of the `idf_component.yml`.
#
# This field is optional.
git = "https://github.com/espressif/esp32-camera.git"
# A path to the component.
# Corresponds to the `path` field of the `idf_component.yml`.
#
# Note: This should not be used for local components, use
# `component_dirs` of extra components instead.
#
# This field is optional.
path = "path/to/component"
# A url to a custom component registry. Corresponds to the `service_url`
# field of the `idf_component.yml`.
#
# This field is optional.
service_url = "https://componentregistry.company.com"

For example, to add a dependency the 1.2.x version of the espressif/mdns component, add the following to your Cargo.toml:

[[package.metadata.esp-idf-sys.extra_components]]
remote_component = { name = "espressif/mdns", version = "1.2" }

Note
Slashes (/) in a remote component's name will be replaced with two underscores __ for the name of the compiled component (e.g. espressif/mdns will become espressif__mdns with the cfg esp_idf_comp_espressif__mdns_enabled).

Remote components that are not already included inside the esp-idf-sys bindings.h file must be manually added, in its own C header file.

For example, the espressif/esp32-camera component could be included in the following way:

[[package.metadata.esp-idf-sys.extra_components]]
remote_component = { name = "espressif/esp32-camera", version = "2.0.7" }
bindings_header = "your_bindings.h"
bindings_module = "camera"

and the your_bindings.h file could look like this:

#if defined(ESP_IDF_COMP_ESPRESSIF__ESP32_CAMERA_ENABLED)
#include "esp_camera.h"
#endif

In this case the bindings would be generated in the esp_idf_sys::camera module.

Conditional compilation

The esp-idf-sys build script will set rustc cfgs available for its sources.

Important

If an upstream crate also wants to have access to the cfgs it must:

  • have esp-idf-sys as a dependency, and

  • output the cfgs in its build script with

    embuild::espidf::sysenv::output();

    using the embuild crate.

The list of available cfgs:

  • esp_idf_comp_{component}_enabled for each component

  • esp_idf_version="{major}.{minor}"

  • esp_idf_version_full="{major}.{minor}.{patch}"

  • esp_idf_version_major="{major}"

  • esp_idf_version_minor="{minor}"

  • esp_idf_version_patch="{patch}"

  • esp_idf_{sdkconfig_option}

    Each sdkconfig setting where {sdkconfig_option} corresponds to the option set in the sdkconfig lowercased, without the CONFIG_ prefix and with a lowercase esp_idf_ prefix. Only options set to y will get a cfg.

  • {mcu}

    Corresponds to the mcu for which the esp-idf is compiled for.

More info

If you are interested in how it all works under the hood, check the build.rs build script of this crate.