bazel_esp32

This repo contains a custom c++ toolchain setup for the bazel build system. It allows you to use the standard cc_library and cc_binary to build esp32-compatible binaries.

Note that these rules are currently only supported on amd64 linux systems. Pull requests are welcome to add support for other systems.

Usage

In your WORKSPACE file load the toolchain dependencies:

load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")

git_repository(
    name = "bazel_esp32",
    branch = "main",
    remote = "https://github.com/simonhorlick/bazel_esp32.git",
)

load("@bazel_esp32//:deps.bzl", "bazel_esp32_dependencies")

bazel_esp32_dependencies()

Add the toolchain configuration to your .bazelrc in the root of your repository:

build:esp32 --crosstool_top=@bazel_esp32//toolchain:esp32
build:esp32 --cpu=xtensa
build:esp32 --host_crosstool_top=@bazel_tools//tools/cpp:toolchain

In this example, hello.cc contains the standard Arduino setup and loop functions. To build a binary that we can run we must add the Arduino main.cc into the cc_binary srcs which in turn calls out to setup and loop.

cc_binary(
    name = "hello",
    srcs = ["@arduino_esp32//:cores/esp32/main.cpp"],  # main entry point.
    deps = [
        ":hello_lib",
        "@arduino_esp32//:core_c_lib",
        "@arduino_esp32//:core_lib",
    ],
)

cc_library(
    name = "hello_lib",
    srcs = ["hello.cc"],
    deps = [
        # note that Arduino libraries must be specified as normal c++ dependencies.
        "@arduino_esp32//:SPI",
    ],
)

To build ensure you are using the esp32 configuration, like so:

$ bazel build --config=esp32 //:hello
INFO: Analyzed target //:hello (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
Target //:hello up-to-date:
  bazel-bin/hello
INFO: Elapsed time: 0.610s, Critical Path: 0.01s
INFO: 1 process: 1 internal.
INFO: Build completed successfully, 1 total action

$ file bazel-bin/hello
bazel-bin/hello: ELF 32-bit LSB executable, Tensilica Xtensa, version 1 (SYSV), statically linked, not stripped

Examples

To flash a device:

bazel build --config=esp32 //:gen_partitions
bazel build --config=esp32 //:gen_image
esptool.py --chip esp32 -p /dev/cu.usbserial-0001 --baud 460800 --before default_reset --after hard_reset write_flash -z --flash_mode dio --flash_freq 80m --flash_size detect 0xe000 /home/simon/.arduino15/packages/esp32/hardware/esp32/2.0.0-alpha1/tools/partitions/boot_app0.bin 0x1000 /home/simon/.arduino15/packages/esp32/hardware/esp32/2.0.0-alpha1/tools/sdk/esp32/bin/bootloader_qio_80m.bin 0x10000 bazel-bin/hello.bin 0x8000 bazel-bin/hello.partitions.bin