A 2.4-GHz WirelessUSB Radio-on-a-chip For Human Interface Devices

Introduction

Cycle times for designing wireless human interface device (HID) products have decreased dramatically over the past few years. Time to market has become key, and taking a wireless keyboard and mouse from initial design phase through production now takes between two and four months. System engineers need their vendors to provide a chip solution that will help them meet this short design cycle. They also expect the chip solution to be noise tolerant and support long battery life.

Cypress Semiconductor recently introduced the WirelessUSB LP radio-on-a-chip to meet the demands of HID systems designers. WirelessUSB LP combines low power and cost, intelligent features, and an interference-immune radio with a lightweight power-sensitive protocol in a 2.4-GHz RF solution. From the physical layer to the transport layer, WirelessUSB LP has been optimized for computer peripherals, sensors, remote controls, and other low-power, low-data-rate devices. This article provides an overview of the WirelessUSB LP Radio and the WirelessUSB Protocol.

WirelessUSB LP radio

Direct-sequence spread spectrum
WirelessUSB LP utilizes a 2.4-GHz direct-sequence spread spectrum (DSSS) radio interface. DSSS uses a pattern for each data bit to be transmitted called a pseudo noise (PN) code. Each bit in the PN code is called a chip, and each instance of the PN code is called a symbol. Data is typically transmitted by transmitting the PN code as a 1, and transmitting the inverse of the PN code as a 0.