This UPS Does Not Come In Brown - Three Essentials For The USB

The Universal Serial Bus, or USB, is an external data bus, or a collection of wires that connects a computer to peripheral devices, that supports data transfer. One USB port can connect up to 127 different peripheral devices, including modems, mice, and keyboards. A USB port also supports hot plugging, which is the computer system's ability to automatically configure devices and expansion boards. Plug and play eliminates the need to set up jumpers, DIP switches, and other configuration elements.

In addition a USB port can support hot plugging, which is the ability to remove and add devices to a computer while it is still turned on. With hot plugging, the operating system automatically recognizes the device without having to reboot the system.

USB ports started to be added as a standard feature to some computers as long ago as 1996. Now, USB ports are becoming a more standard addition to computers and they are expected to totally replace parallel and serial ports as a standard computer feature.

To properly utilize an USB port, it is important to understand a few basics.

1) A USB port works differently than a parallel or a serial port. A USB port does not have its own unique port address, like parallel and serial ports. Therefore, a device attached to the computer via a USB port causes the operating system to request to receive information from the connected device. The USB port then assigns a bus address and a class driver for the device to communicate with the computer. Lower-level drivers usually provide this communication. For Windows users, Windows will assign the way an application or device communicates with the USB depends and which device driver is assigned.

2) Two PCs can be connected with through USB ports. Since all communication through USB is between a device and a host, an EZ-link can be used to bridge two USB ports. An EZ-link contains two USB devices and each connects to a different PC. The data that is sent to one devise is then passed to the other device, which sends the data on to the second PC. This type of connection is usually used in network connections between PCs.

Two PCs can also be connected using a USB/RS-232 adapter for each PC. The RS-232 ports are then connected via a null-modem connection and the COM-port is able to function as communicator between the two PCs rather than through the USB port.

Another option for transferring data between two PCs is to install a device card, such as PLX Technology's NET2280EVB Adapter card, in one PC containing an USB port. The PC then provides the driver software for the device, making it then capable of communicating with an additional PC.

A parallel port from one computer can also control a USB device using programs such as DevaSys USBLPT-PD11. This board allows an ordinary PC to become the target of USB device hardware by using a second PC with an USB port as the host.

3) A USB driver or USB peripheral can also be connected to a microcontroller circuit. One way to do this is to add an embedded host controller to the microcontroller unit. This can work because all USB communication takes place between a device and a host. Nearly all microcontrollers with the ability to use USB are considered devices, as are all peripherals.

A peripheral containing USB on-the-go capability can also be used. In this way, the peripheral can be used as a host as well as a device. Philip's ISP1261 Bridge Controller can be used to convert a device function to on-the-go.

A Delkin USB Bridge can also be used to transfer files between two devices. This device allows for data, images, and music files to be copied from a USB compliant device to a different device, but it does not require the assistance of a computer. For example, images can be removed directly from a digital camera to a portable storage device without having to go through a computer.

Another option is to directly connect the microcontroller and the peripheral to a USB host or PC.

USB ports are becoming increasingly common and provide an excellent way to connect devices and peripherals or to link two computers together.