---
title: "Control LED systems"
slug: "control-led-systems"
updated: 2025-09-15T13:47:11Z
published: 2025-09-15T13:47:11Z
canonical: "docs.grassfish.com/control-led-systems"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.grassfish.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Control LED systems

This article describes how to control an external LED system through runtime commands sent to the Grassfish Player.

These commands are issued using the **sendMessageToPlayer** method of the GFSpotBase interface.

## Command syntax

The LED control interface follows a simple command protocol. The commands are interpreted by the player and routed to the physical or simulated LED device.

> [!NOTE]
> Note
> 
> Command processing depends on the player type and version. For example, the Android player can interpret LED commands natively without additional configuration. Other platforms, such as Qt-based players, may require an additional LED control add-on for full functionality.

---

#### Turn LED on with color:

`sendMessageToPlayer("LEDOn", "<hexColor>");`

- **"LEDOn"**: Use this command to switch on the LED.
- **<hexColor>**: Specify the LED’s color using the RGB color value in hexadecimal format (#FF0000).

---

#### Turn LED off:

`sendMessageToPlayer("LEDOff");`

- **"LEDOff"**: Use this command to switch off the LED entirely.

---

## Access the interface

To communicate with the player, the spot must include the gfSpotBase.js library. This JavaScript file is typically added as a script dependency and is responsible for providing the global GFSpotBase object.

To include the library globally, use the following command:

`window.GFSpotBase = new GFSpotBase(); `

This makes the API accessible throughout the spot runtime.

> [!NOTE]
> Note
> 
> Before using any methods, the spot should check whether **window.GFSpotBase** is available to avoid runtime errors.

## Example implementation

The following example shows a minimal implementation using a service-based abstraction:

```javascript
private setLedOn(hexColor: string | null) {
  if (hexColor) {
    GfSpotBaseService.sendMessageToPlayer("LEDOn", hexColor);
  }
}

private setLedOff() {
  GfSpotBaseService.sendMessageToPlayer("LEDOff");
}
```

## Abstraction layer

This example shows how to use a common approach to encapsulate GFSpotBase access in a service class:

- This wrapper provides a safe abstraction for all player communication tasks, including LED control.
- We recommended to use such a structure to improve modularity, testability, and error handling.

```javascript
class GfSpotBaseService {
  private _spotBase: any;

  constructor() {
    if (window.GFSpotBase) {
      this._spotBase = window.GFSpotBase;
    } else {
      throw "NoSpotBaseException";
    }
  }

  sendMessageToPlayer(...args: (string | number)[]): void {
    this._spotBase.sendMessageToPlayer(...args);
  }
}
```

An add-on is a software extension or enhancement that adds new features or functionality.