Appliance Design - October 2007 - (Page 30)

ELECTRONICS Fig. 1. A fast-food chain uses USB to program oven controls with new menu items. USING USB Adding USB host capability increases appliance flexibility. ost everyone is familiar with USB, the Universal Serial Bus; it is an incredibly successful technology for providing communication between personal computers and peripherals, and there are millions of nodes in service around the world. USB was originally designed to provide the end user with an extremely simple method for plugging peripherals to a host, such as adding a printer to a PC. USB is now a family of standards managed by the USB Implementers Forum. (See www.usb.org.) The current core standard is USB 2.0, or Hi-Speed USB. This operates over wires at up to 480 Mbps, but also includes the original USB standard (USB 1.1) for applications where a data rate of 12 Mbps is sufficient (or even the low speed mode of 1.5 Mbps). Additionally, there are standards based on USB 2.0 for wireless use (Wireless USB) and, to cope with needs of portable equipment, USB On-The-Go (technically a supplement to USB 2.0). Wired USB has a host-based star topology. M by fred dart Fred Dart is CEO, Future Technology Devices International Ltd., Glasgow, Scotland. 30 applianceDESIGN October 2007 Arms of the star can also themselves be stars and ultimately they terminate in peripherals. (With USB On-The-Go, devices can act as both hosts and peripherals.) The USB host controller, which is essential for communicating with all USB peripherals, is defined by the USB Host Controller Interface specification, while USB Class Specifications cover selected groups of related USB peripherals. For example the Human Interface Device (HID) Class Specification covers such devices as keyboards, mice, joysticks etc. Like TCP/IP, USB software is designed as a stack of layers, with the lowest layer providing the interface with the hardware and the highest providing interface to applications or the OS. A USB-Host stack will typically consist of a host controller capability at the lowest level with a middle, services layer handling device connection and disconnection, device initialization, driver selection and resource management, and a top level, containing the different drivers for the different classes of devices, making the device available to the OS www.applianceDESIGN.com http://www.usb.org http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - October 2007

Contents Editorial Shipments/Forecasts News Watch Applying Powder Coatings to Plastic Parts is No Longer a Pipe Dream New Technology Platform Provides the Ability for a single IC to Control Two- Motors in a Single Appliance, Simplifying Motor Control Design Advanced Motor-Control Techniques have Become More Accessible to a Wider Array of Appliances, Helping to Improve Efficiency and Reduce Noise Adding USB Host Capability to Appliances Permits In-Field Programming and Acquisition of Test Data ZigBee Modules Make it Easier to Design Wireless Connectivity into Applications New Concepts such as Rapid Tooling and Rapid Injection Molding Provide Stepping Stones Between Prototyping and Full Scale Production A Number of Factors and New Developments Affect the Decision on Whether to Build Prototypes In-House or Outsource to a Service Bureau DesignMart Advertiser’s Index Association Report: CEA

Appliance Design - October 2007

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