Rust bindings for ESP-IDF

(Espressif's IoT Development Framework)

Background

The ESP-IDF API in Rust, with support for each ESP chip (ESP32, ESP32S2, ESP32S3, ESP32C3 etc.) based on the Rust target.

For more information, check out:

• The Rust on ESP Book
• The esp-idf-template project
• The esp-idf-svc project
• The esp-idf-hal project
• The Rust for Xtensa toolchain
• The Rust-with-STD demo project

Build

• To build this crate, please follow all the build requirements specified in the ESP-IDF Rust Hello World template crate
• The relevant Espressif toolchain, as well as the ESP-IDF framework itself are all automatically downloaded during the build:
  • With feature native (default): utilizing native ESP-IDF tooling via the embuild crate or
  • With feature pio (backup): utilizing PlatformIO (also via the embuild crate).
• Check the ESP-IDF Rust Hello World template crate for a "Hello, world!" Rust template demonstrating how to use and build this crate.
• Check the demo crate for a more comprehensive example in terms of capabilities.

Feature 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.

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

TBD: Upcoming

Feature 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.

NOTE: 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.

(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

Configuration

Environment variables are used to configure how the ESP-IDF framework is compiled.

Note that instead of / in addition to specifying those on the command line, you can also put these in a .config/cargo.toml file inside your crate directory (or a parent directory of your crate) by using the recently stabilized Cargo configurable-env feature.

The following environment variables are used by the build script:

• ESP_IDF_SDKCONFIG_DEFAULTS:

  A ;-separated 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 cargo workspace directory (i.e. the directory that contains the target dir).

  If unspecified sdkconfig.defaults is used as default.

  For each defaults file in this list more specific version 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).

  Also note that a setting contained in a more specific defaults file will override the same setting specified in a less specific one.

• ESP_IDF_SDKCONFIG:

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

  If unspecified sdkconfig is used as default.

  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:

  The location where the ESP-IDF framework tooling is assumed to be/will be installed. The framework tooling is either PlatformIO (when the pio builder is used), or the ESP-IDF native toolset (when the native builder is used).

  This variable can take one of the following values:

  • workspace (default) - the tooling will be installed/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/used inside the crate's build output directory, and will be deleted when cargo clean is invoked;

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

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

  • 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.

  ATTENTION: 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.

  Note that both builders (native and pio) clone the ESP-IDF GIT repository inside the tooling directory as well. This restriction might be lifted soon for the native builder, whereas the user would be able to point the build to a custom ESP-IDF repository location.

• 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 (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.

  It defaults to v4.3.2.

• 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 that 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 .

• 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 follwing 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 in theESP-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 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 also that this is not one variable - but rather - a family of variables all starting with ESP_IDF_PIO_CONF_. I.e., 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 (native builder only):

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

• MCU:

  The MCU name (i.e. esp32, esp32s2, esp32s3 esp32c3 and esp32h2).

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

  • Note that older ESP-IDF versions might not support all MCUs from above.

More info

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