Using MicroPython with a NodeMCU

Download MicroPython firmware

Download the firmware from http://micropython.org/download#esp8266

wget http://micropython.org/resources/firmware/esp8266-20180511-v1.9.4.bin

Install esptool for flashing the NodeMCU

pip install esptool

Flash the MicroPython firmware to the NodeMCU

Start the NodeMCU in ROM Flash Mode

• Connect the power to the NodeMCU while holding down the Flash button.
• The flash button will startup the NodeMCU in ROM flash mode.

Connect the NodeMCU using a USB Hub or external power supply

• The NodeMCU will draw 5.5v of power.
• If you are programming the NodeMCU using a Raspberry Pi, you will find that the power draw will be too large and your Raspberry Pi will shutdown.
• I find it easiest to connect to the NodeMCU through a powered USB hub.

Erase the NodeMCU

esptool.py --port /dev/ttyUSB0 erase_flash

Write the rom to the NodeMCU

esptool.py \
  --port /dev/ttyUSB0 \
  --baud 115200 write_flash \
  --flash_size=detect 0 \
  esp8266-20180511-v1.9.4.bin

• After flashing the NodeMCU with MicroPython, recycle the power on it twice.

Connect to the MicroPython NodeMCU

Connect to the MicroPython NodeMCU using minicom

minicom --baudrate 115200 --device /dev/ttyUSB0

Verify the MicroPython firmware

import esp
esp.check_fw()

The Internal Filesystem

• When the NodeMCU boots the MicroPython framework for the first time, a FAT filesystem will be setup in the firmware.

• The filesystem can be accessed over (Web)REPL using the appropriate client.

List files via REPL

import os
os.listdir('')

Startup Scripts

• There are two startup scripts: boot.py and main.py

• boot.py is executed first
• main.py is executed second

Read the list of files on the filesystem using Python

import os
print(os.listdir())

Read the contents of a file using Python

with open("boot.py", "r") as f:
  print(f.read())

with open("webrepl_cfg.py", "r") as f:
  print(f.read())

Write the contents of a file using Python

with open("myfile.txt", "w") as f:
  f.write("Hello world!")

Configure Wifi

After getting the NodeMCU running MicroPython, the wifi can be configured.