LED HTTP Service for ALLNET Meeting Room Tablet (RK3399)

Overview

LED HTTP Service is an Android application specifically designed for the ALLNET Meeting Room RGB LED Tablet RK3399 Android 10. It acts as a bridge between your network and the tablet's hardware LED bar, exposing a local HTTP API to control the light frame remotely.

The app is built to be a robust background utility, running as a persistent Foreground Service that automatically starts on system boot. It handles complex hardware behaviors, such as mandatory display activation and state-dependent timing, ensuring reliable LED control for integration with room booking systems and automation platforms.

Features

• Local HTTP API: Lightweight NanoHTTPD server running on port 8080.
• Hardware LED Control: Direct manipulation of the RGB LED bar via root-level sysfs commands.
• Adaptive Hardware Timing: Detects if the display was off and applies robust delays and retries to ensure command registration.
• Smart Display Management: Automatically wakes the tablet display before every LED command sequence.
• Persistent State: Remembers the last set mode across service restarts and reboots.
• Auto-Start on Boot: Automatically initializes the service when the tablet finishes booting.
• Foreground Service: Maintains a persistent background process with a system notification.
• Material 3 Dashboard: Polished, tablet-optimized local UI to monitor status and manually test modes.

Hardware / Target Device

This application is specifically developed and tested for:

• Device: ALLNET Meeting Room RGB LED Tablet RK3399 Android 10 (10" or 15" variants).
• Chipset: Rockchip RK3399.
• OS: Android 10 (API 29).
• Requirement: The device must have root access for the shell commands to reach the hardware platform.

How It Works

Hardware Command

The LED bar is controlled by writing specific hex codes to the kernel's platform driver: sh -c "echo 'w $CODE' > /sys/devices/platform/led_con_h/zigbee_reset"

Intelligent Wakeup & Timing

On this hardware, the LED controller is only reliable when the display is active. The app handles this automatically:

1. Detection: Checks PowerManager.isInteractive() to see if the screen was off.
2. Wakeup: Executes input keyevent KEYCODE_WAKEUP.
3. Adaptive Delay:
   • If display was OFF: Waits 4000ms (4s) for hardware initialization.
   • If display was ON: Waits 250ms.
4. Sequence Reliability:
   • If the display was previously off, the app automatically retries the target LED command after a 250ms interval to ensure the hardware bus processes the change.

Power-On Logic

If the device is currently in the off mode, it must be logically "powered on" before a color can be applied. When switching from off or unknown to a color/effect, the app sends the internal on (0x03) command and waits 500ms before applying the final target mode.

LED Modes

The following modes are supported by the public API, listed in their logical order:

Power

• off, on

Base Colors

• red, green, blue, white

Extended Colors

• orange_red, orange, yellow_orange, yellow, turquoise, light_blue, cyan, medium_blue, blue_green, violet, purple, pink

Dynamic Effects

• flash, strobe, fade, smooth

HTTP API

The server listens on port 8080.

Endpoints

1. Home / Dashboard

GET / Returns a tablet-friendly HTML control panel for manual interaction.

2. Health Check

GET /health

• Response: {"success": true}

3. Service Status

GET /status

• Response:

  {
    "success": true,
    "service": "led-http-service",
    "lastMode": "red"
  }

4. List Available Modes

GET /modes

• Response: {"modes": ["off", "on", ... ]}

5. Wake Display

GET /wake

• Response: {"success": true, "action": "wake"}

6. Set LED Mode

GET /led?mode={name} or GET /led/{name}

• Parameters: mode (string)
• Response: {"success": true, "mode": "green"}
• Error Response: {"success": false, "message": "Failed to set LED for mode: ..."}

7. Help

GET /help

• Response: Returns a JSON list of all available endpoints and usage hints.

Example curl Commands

# Set mode to red
curl "http://TABLET_IP:8080/led?mode=red"

# Turn LED off
curl "http://TABLET_IP:8080/led/off"

# Get current state
curl "http://TABLET_IP:8080/status"

Build Instructions

1. Open the project in Android Studio.
2. Sync Project with Gradle Files.
3. Build the APK via Build > Build Bundle(s) / APK(s) > Build APK(s).

Alternatively, use the Gradle wrapper from the terminal:

./gradlew assembleDebug

Installation

1. Enable USB Debugging on the tablet.
2. Install the APK via ADB:

   adb install app-debug.apk

3. Open the app once to grant any necessary permissions and allow the root manager (e.g., Magisk) to grant root access.

Permissions & Android Behavior

The app declares and uses the following:

• INTERNET: For the NanoHTTPD server.
• RECEIVE_BOOT_COMPLETED: To start the service automatically after restart.
• WAKE_LOCK: To ensure the CPU stays active during command processing.
• FOREGROUND_SERVICE: To maintain a persistent background state.
• usesCleartextTraffic="true": Required for HTTP local network access.

Project Structure

• LedService: Manages the lifecycle of the HTTP server and the foreground notification.
• LedHttpServer: Implements the NanoHTTPD logic and endpoint routing.
• LedController: Core logic for state persistence, color mapping, and adaptive timing.
• ShellExecutor: Robustly executes root commands and captures ShellResult (success, exitCode, stdout, stderr).
• WakeHelper: Checks interactive state and manages display wakeup.
• BootReceiver: Triggers the service on system startup.
• MainActivity: Provides the Material 3 dashboard UI.

Notes & Caveats

• Root Required: This app will not function without root access. It must be able to call su.
• Hardware Specific: Tested exclusively on the ALLNET RK3399 series.
• Display Dependency: LED commands are only reliable when the display is awake. The app handles this, but the display will briefly turn on during every LED change.

License

This project is licensed under the MIT License. See the LICENSE file for details.