How To Write Micropython Firmware to the Wemos D1 Mini

All Wemos D1 Minis I tested required a different flash mode than shown in the official documentation to successfully write the Micropython firmware to the module.

The following commands resulted in a succesfull write. –port [usbdevice] –baud 115200 erase_flash –port [usbdevice] –baud 115200 write_flash -fm dio –flash_size=detect 0 [firmware.bin]

HowTo Build MicroPython for ESP32 on OSX

A prebuild toolchain for the ESP32 is available from Espressif:

If you’re interested in building from scratch check the docs for IDF v.3.3

Get MicroPython and initialise its dependencies
git clone
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
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
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.