Intro

• I wanted to program my ESP8266 over the Wireless LAN in real time so I created this library.

pyWebREPL

• micropython/webrepl provides a browser-based client to control ESP32/ESP8266 but it is not for real automation.
• I did a reverse-engineering work with the help of Wireshark and Chrome Devtools.
  

Know problem

As of 24 Nov 2022, the network config of ESP32 is not persistent (it loses WIFI connection after power-off), esp8266 is OK. A workaround is putting the following code in the main.py. I will automate this procedure in the future.

import network                         
wlan = network.WLAN(network.STA_IF)    
wlan.active(True)                       
wlan.connect(SSID, WIFI_PASSWD)   

Material List

• ESP32/ESP8266 dev board
• Raspberry Pi (OR any Linux)
• WiFi router (Pi is already connected to this router)

Follow this section and skip others if you only want blink ESP32/ESP8266 over the WiFi.

• For one time, a USB cable is still necessary to connect ESP32/ESP8266 to the Raspberry Pi.
• Run following commands on Raspberry Pi.

sudo apt update && sudo apt install python3 python3-pip
pip install esptool
git clone -b v1.2 https://github.com/xg590/pyWebREPL.git
cd pyWebREPL
wget https://micropython.org/resources/firmware/esp8266-20220618-v1.19.1.bin && wget https://micropython.org/resources/firmware/esp32-20220618-v1.19.1.bin
bash misc/flash_adv.sh --model esp8266 --port /dev/ttyUSB0 --bin esp8266-20220618-v1.19.1.bin --hostname myESP8266 --webrepl-passwd 123456 --ssid xxx --wifi-passwd xxx
bash misc/flash_adv.sh --model esp32   --port /dev/ttyUSB0 --bin   esp32-20220618-v1.19.1.bin --hostname myESP32   --webrepl-passwd 123456 --ssid xxx --wifi-passwd xxx
tail -n4 flash.log

• The last tail command reveals what IP is given by a WiFi router to the ESP32/ESP8266 board.
• After run these commands, ESP32/ESP8266 can be detached from Raspberry Pi and powered by a separate USB charger.
• Blink ESP32/ESP8266 with pyWebREPL over the WiFi.

python3 example/blink.py 192.168.x.xxx 

Mechanism

• Flash the ESP32/ES8266 dev board with MicroPython firmware then one can get a MicroPython prompt for the ESP32/ESP8266.
• Enable MicroPython's WebREPL feature and join ESP32/ESP8266 to a WiFi network so that the prompt can be accessed as a webservice.
• Before pyWebREPL, there is a broswer client for us to talk to the webservice.
• This library provide a Python client for Raspberry Pi to talk to the webservice.

More Deeper

• The webservice uses the websocket protocol
• This Python library for Raspberry Pi converts the MicroPython code into websocket frames
• Frames are sent to the webservice then MicroPython code will be interpreted on ESP32/ESP8266 in real time.

A few words about MicroPython prompt (Nonprinting Characters)

• In the MicroPython prompt, when we press ctrl+e (its caret notation is ^E) on keyboard, we activate the paste mode.
• If we refers to Control code chart of ASCII, we know ^E is "\x05", so we can activate the paste mode when we send b"\x05" via webREPL. Then our code will be received in paste mode, which is how we run code block.

Update log

• New for v1.2 see example
  • Add two new functions: write_main and soft_boot.
  • main.py is executed automatically after the boot of MicroPython interpreter. write_main create or update the main.py in root directory.