Plugged into it, from the host’s point of view (a common USB host is a desktop computer.) The The USB drivers for a host system control the USB devices that are The Linux kernel supports two main types of USB drivers: drivers on a host system andĭrivers on a device. The need to shut the system down, open the cover, and swear over screws and wires. Handy, low-cost mechanism to connect (and disconnect) several devices to the computer without These features, together with the inherent hotplug capability of the design, make USB a Video devices and USB-to-serial devices are a good example where there is noĭefined standard, and a driver is needed for every different device from different Other types of devices thatĭo not fit into these classes require a special vendor-specific driver to be written for that These different types are called classes and consist of things like storageĭevices, keyboards, mice, joysticks, network devices, and modems. If a device follows that standard, then a special driver for that device is The USB protocol specifications define a set of standards that any device of a specific Limitation, the bus has some interesting features, such as the ability for a device to requestĪ fixed bandwidth for its data transfers in order to reliably support video and audio I/O.Īnother important feature of USB is that it acts merely as a communication channel between theĭevice and the host, without requiring specific meaning or structure to the data it In which the host computer polls the various peripheral devices. The bus is very simple at the technological level, as it’s a single-master implementation This configuration allows for a very easy plug-and-play type of system, wherebyĭevices can be automatically configured by the host computer. Topology, a USB device can never start sending data without first being asked to by the hostĬontroller. The USB hostĬontroller is in charge of asking every USB device if it has any data to send. Wires) that connect a device and a hub, just like twisted-pair Ethernet. The links are four-wire cables (ground, power, and two signal Topologically, a USB subsystem is not laid out as a bus it is rather a tree built out of High-speed connections with a theoretical speed limit of 480 MBps. The latest revision of the USB specification added USB has grown beyond these slow connections and now supports almost every type ofĭevice that can be connected to a PC. It was originally created to replace a wide range of slow andĭifferent buses-the parallel, serial, and keyboard connections-with a single bus type that allĭevices could connect to. The universal serial bus (USB) is a connection
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