A prebuild toolchain for the ESP32 is available from Espressif: https://dl.espressif.com/dl/xtensa-esp32-elf-osx-1.22.0-80-g6c4433a-5.2.0.tar.gz
If you’re interested in building from scratch check the docs for IDF v.3.3 https://docs.espressif.com/projects/esp-idf/en/v3.3/get-started/macos-setup.html
Get MicroPython and initialise its dependencies
git clone https://github.com/micropython/micropython.git
git submodule update --init
Get the correct version of the IDF and its dependencies
As of 09/2019 the MicroPython build needs v3.3 of the IDF. Later versions use cmake instead of make.
git clone https://github.com/espressif/esp-idf.git
git checkout 6ccb4cf5b7d1fdddb8c2492f9cbc926abaf230df
git submodule update --init --recursive
Unpack the toolchain and add IT to the PATH
tar -zxf xtensa-esp32-elf-osx-1.22.0-80-g6c4433a-5.2.0.tar.gz
export PATH=$PATH:<replace with absolute path to toolchain>/bin
Virtual Environment
Some of the build tools and dependencies require Python 3. Lets create a virtual environment and activate it to keep things separated.
virtualenv --python=python3 esp32buildEnv
source esp32buildEnv/bin/activate
Install the python dependencies required by the IDF
pip install -r esp-idf/requirements.txt
Build the crosscompiler
cd mpy-cross
make
Build the ESP32 port
cd ports/esp32
ESPIDF=<path to IDF root> PYTHON2=/usr/bin/python make
The resulting “firmware.bin” can be uploaded to your ESP32 with the “esptool” as usual.