4-Letter 14-Segment indicator toy

Hardware

• M5 Stamp-C3U - ESP32-C3 MCU module
• SparkFun Qwiic Alphanumeric Display - Blue
• Grove to STEMMA QT / Qwiic / JST SH Cable - 100mm long

Software & SaaS services

• PyCharm
• MicroPython plugin
• Google Blockly is used to edit and run display programs online.
  • The blocks are converted to JavaScript code to be run in the browser window
  • The blocks are converted to MicroPython code to be run on MCU side
• GitHub pages hosts the web part
• EMQ Free Public MQTT Broker helps to exchange data between web- and hardware- part
• MicroPython is run on the ESP32 MCU and handles both the display and MQTT connection
• HT16K33 Python driver
• micropython-mqtt

How2Run

1. Solder the Grove connector (shipped with the module) to M5 Stamp-C3U Port A
2. Connect the display module to the MCU module
3. Connect the MCU module to your computer with USB cable. A COM port should appear
4. Flash latest MicroPython to the MCU module. JS ESPTool is a handy tool for it. Note that .bin file should be flashed at address 0x0000
5. Create a (free) account at a public MQTT broker (ex https://www.hivemq.com/, https://www.emqx.io/)
6. Create your own cloud MQTT broker
7. Create an MQTT user. NB! Create a strong password and keep it well, otherwise your WLAN may be hacked!
8. Write your own SECRETS.py file based on the template secrets_template.py. There should be your specific Wi-Fi SSID, Wi-Fi password, and MQTT lo.
9. Upload newly created SECRETS.py to the MCU module filesystem. You may use either PyCharm with MicroPython plugin, Thonny, or mpremote
10. Upload MicroPython code to the MCU board. The tools are above
11. Reboot the board
12. Open elmot.xyz/esp32-blockly-display/
13. Click gear icon and enter your MQTT parameters, same as in MicroPython part
14. If everything is done correctly, The board connects to the MQTT broker
    • Wi-Fi sign on the web page turns to be dark green
    • On-Board LED turns green after several seconds

On-board led statuses

• Blue blinking => Wi-Fi connection in progress
• Red steady => Wi-Fi connection failed
• Yellow steady => MQTT connection in progress
• Green steady => MQTT connection established

Technical details

Blocks are stored to browser's local storage.