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ESP32 BLE LED Control

MicroPython + Bluetooth Low Energy

Project Overview

This project demonstrates controlling the onboard LED of an ESP32 via Bluetooth Low Energy (BLE) using MicroPython. Any BLE UART-compatible smartphone app (such as nRF Connect) can be used to send commands and toggle the LED wirelessly.

Features

  • BLE UART Communication — Uses the Nordic UART Service (NUS)
  • LED Control — Toggle LED via LED_ON / LED_OFF commands
  • Status Query — Query the current LED state with the STATUS command
  • Connection Indicator — LED blinks when disconnected, solid ON when connected

Hardware Requirements

Component Details
Microcontroller ESP32 DevKit v1
Onboard LED Pin GPIO 2
LED Type Standard LED
BLE Support Built-in
MicroPython v1.19+

Software Requirements

  • MicroPython firmware flashed on the ESP32
  • Thonny IDE — for uploading code to the board
  • nRF Connect app (Android/iOS)
  • ubluetooth module (built into MicroPython)

BLE Commands

Command Action Board Response
LED_ON Turn the LED ON LED is ON
LED_OFF Turn the LED OFF LED is OFF
STATUS Query LED state LED is ON / LED is OFF

LED Behavior

LED State Meaning
Blinking BLE Disconnected (advertising)
Solid ON BLE Connected
OFF LED_OFF command received

How to Use

  1. Flash MicroPython onto your ESP32 — micropython.org
  2. Upload the code using Thonny IDE and click Run
  3. Open nRF Connect app on your smartphone
  4. Scan for devices — look for ESP32
  5. Connect and navigate to the TX Characteristic
  6. Enable Notifications on the TX Characteristic (tap the bell icon)
  7. Write LED_ON to the RX Characteristic and send

BLE Service UUIDs (Nordic UART Service)

Service / Characteristic UUID
Nordic UART Service (NUS) 6E400001-B5A3-F393-E0A9-E50E24DCCA9E
RX Characteristic (Write) 6E400002-B5A3-F393-E0A9-E50E24DCCA9E
TX Characteristic (Notify) 6E400003-B5A3-F393-E0A9-E50E24DCCA9E

Troubleshooting

Problem Solution
OSError: -128 on send Enable Notifications on TX Characteristic in nRF Connect
LED not responding to commands Check that GPIO 2 is the correct LED pin on your board
Device not visible during scan Restart the board and scan again
BLE not working at all Ensure MicroPython v1.19+ with ubluetooth support

Author

Kritish Mohapatra

B.Tech Electrical Engineering — 3rd Year

IoT | Embedded Systems | MicroPython | ESP32

OUTR, Bhubaneswar

⭐ Support

If you found this project helpful, give it a ⭐ on GitHub and feel free to fork it!

Happy Hacking! 🚀