LED shield

LightAlarmClock

A hardware-software alarm clock system that combines an Android app, BLE communication, and an ESP32 firmware controller to trigger a pre-alarm light sequence before the alarm rings.

This project demonstrates end-to-end product engineering across mobile, embedded firmware, and electronics design.

Why this project

Traditional alarms wake you up abruptly with sound. LightAlarmClock introduces a softer wake-up flow:

1. 10 minutes before alarm: Android app sends a BLE command
2. ESP32 receives command: firmware starts a timed IR/light transmission sequence
3. Alarm time: full alarm rings on phone with dismiss/snooze UI

This creates a practical blueprint for a smart alarm + ambient wake-up device.

System Architecture

1) Android App (Android/)

• Built with Kotlin + Jetpack Compose
• Vibecoded Android implementation focused on fast iteration and feature validation
• Lets users:
  • create/edit/delete alarms
  • configure recurring schedules
  • choose ringtone
  • toggle vibration/notification
  • configure BLE target (device address, service UUID, characteristic UUID, message)
• Uses AlarmManager.setExactAndAllowWhileIdle for precise alarms
• Triggers a BLE foreground service (BleMessageService) 10 minutes before alarm
• Launches a full-screen alarm activity (AlarmActivity) and ringing service (AlarmRingingService) at alarm time

2) ESP32 Firmware (Rust - ESP32/)

• Built in Rust using esp-idf-svc + esp32-nimble
• Exposes a custom BLE service/characteristic
• On write, starts a state-machine-driven transmission (PWM + timer interrupts)
• Generates a modulated sequence (38.2 kHz carrier) suitable for IR/light control workflows

3) Hardware Shield (LED_shield/)

• KiCad project for custom LED/IR driver shield
• Includes:
  • schematic (.kicad_sch)
  • PCB layout (.kicad_pcb)
  • Gerber outputs (GBR/)
  • BOM (BOM.csv)
• Components include an IR LED (LD271), regulator (LM7805), and supporting passives/connectors

Key Features

• End-to-end alarm pipeline from mobile UI to physical actuation
• Foreground services for reliable background BLE and alarm behavior
• Lock-screen alarm UX with Snooze / Dismiss actions
• Recurring alarm scheduling and day selection
• Hardware manufacturing assets included (Gerbers + BOM)

Tech Stack

Android

• Kotlin
• Jetpack Compose (Material 3)
• Android AlarmManager / BroadcastReceiver / Foreground Service

Embedded

• Rust (edition 2021)
• esp-idf-svc
• esp32-nimble (BLE stack)

Hardware

• KiCad (schematic + PCB)
• Through-hole + connector-based shield design

Repository Structure

LightAlarmClock/
├── Android/           # Kotlin Android app (UI, alarms, BLE client)
├── Rust - ESP32/      # ESP32 Rust firmware (BLE peripheral + signal generation)
├── LED_shield/        # KiCad hardware design + Gerbers + BOM
└── LICENSE            # GPL-3.0

Getting Started

Prerequisites

• Android Studio (latest stable)
• Android device running API 33+ (for current app config)
• ESP32 development board
• Rust + esp-idf toolchain for ESP32 builds
• BLE-capable phone and ESP32 in range

1) Run Android App

cd Android
./gradlew assembleDebug

Then install from Android Studio or via adb.

2) Flash ESP32 Firmware

From Rust - ESP32/, build/flash with your ESP-IDF Rust setup (tooling varies by environment). The firmware advertises BLE service:

• Service UUID: 6827989e-079a-404f-946a-da39f968ce82
• Characteristic UUID: c696a5a1-827f-4df2-8260-5cdc7f0a4f44

3) Configure BLE in App

In the app:

• Open Bluetooth Settings
• Enter ESP32 MAC address
• Confirm service/characteristic UUIDs
• Set message payload
• Use Test Connection and Send Test Message

Alarm Flow (Runtime)

1. User schedules alarm in app
2. App registers:
   • main alarm trigger
   • BLE pre-alarm trigger (10 minutes earlier)
3. Pre-alarm fires -> BlePreAlarmReceiver starts BleMessageService
4. BLE write triggers ESP32 transmission sequence
5. Main alarm fires -> alarm UI + ringing foreground service
6. User snoozes or dismisses

Recruiter Highlights

This project showcases:

• Cross-domain engineering: mobile + embedded + PCB
• Real-world Android architecture: alarms, receivers, services, lock-screen behavior
• Low-level firmware work: timers, PWM, BLE GATT handling
• System integration mindset: one product, multiple layers, clear signal path
• Product thinking: user-centric wake-up experience, not just a technical demo

Known Improvements / Roadmap

• Add automated tests (unit + instrumentation) for alarm scheduling edge cases
• Improve BLE retry/backoff and connection lifecycle handling
• Add screenshots/GIFs for app UX in this README
• Add hardware bring-up and calibration guide
• Harden production alarm reliability across OEM battery optimizations

License

This project is licensed under GNU GPL v3.0. See LICENSE.