USB composite devices

Most of our USB scanners support 2 interface options:

• USB-HID (Keyboard)
• USB Serial (Virtual COM Port)

You can choose one mode depending on your needs.

The L-250, P-250 and Q-250 are different, they are USB composite devices, meaning they function as both a keyboard and a serial port at the same time over a single USB connection.

What does that mean?

• Keyboard Mode (HID): The scanner sends barcode data as if you typed it—no drivers needed.
• Serial Mode (VCP): At the same time, it appears as a COM port for advanced communication with software or embedded systems.

Advantages of a composite interface:

1. Two modes in one device: Works with both basic and advanced systems.
2. Flexible integration: Easily switch modes using serial commands—no manual reconfiguration required.
3. No extra hardware needed: One device replaces both keyboard and serial-only scanners.
4. Broad compatibility: Supported on most operating systems without additional drivers.
5. Easy setup: Configurable through setup codes or software.
6. Reliable performance: Uses standard USB protocols (HID and CDC), ensuring stability.

Disadvantages of a composite interface:

1. More complex enumeration: The device appears as two USB interfaces, which can confuse some systems or require extra configuration.
2. Compatibility issues on certain platforms: Some embedded systems or older operating systems may not support USB composite devices properly.
3. Increased system resource use: Two interfaces require slightly more USB bandwidth and processing capacity.
4. Software integration complexity: Applications must correctly handle or select the intended interface; simultaneous use may not always be supported.

HID-only configuration available:
For systems that do not support USB composite devices, a HID-only configuration is available. In this mode, the scanner functions strictly as a keyboard input device, ensuring maximum compatibility with limited or older systems.

Summary

The L-250, P-250 and Q-250 offers flexible USB connectivity by combining HID and Serial modes in one device. For systems with limited USB support, a HID-only option ensures simple and reliable integration.

How to switch interface?
Download our guide here to find useful scan QR codes for easily switching between interfaces.