Programming USB HID extender in embedded environments

OData support
Dr. Kovácsházy Tamás
Department of Measurement and Information Systems

The subject of this paper is to design an USB HID (Human Interface Device) signal extender. The device allows us to stream the data of keyboard, mouse or simple HID class devices over fiber optic. The distance between the computer and control devices (keyboards, mice) can be extended with the transmitter-receiver pair up to several kilometers. The goal is to implement the device and the host modules, and to define the protocol between them. My job began with working up a detailed specification based on the preliminary conceptions. First, I had to study the USB specification. Then I shaped up the system’s functional block diagram, and specified the necessary circuit blocks, that could be realized with integrated circuits.

During the development I kept in mind that the device has to be user friendly, and robust, also looking ahead to make future improvements and development easier. According to the early specification requirements, the device is using transparent data transfer. It means that the emulated device shows up with the original parameters. The computer will not see the extender as a connected device.

In the current state of development, the extender device pair’s firmware, schematics, and the test units are done. I had to make the initial setup, testing and had to recommend changes for the final version.


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