USB provides a serial bus standard for connecting devices. USB 1.1, though USB 2.0 is more prominent. The host detects addition and loads the appropriate driver if installed. There are two types of connectors;
- Type A.
- Type B.
- Type A.
- Type B.
Type A sockets found on hosts and hubs. It is always upstream. Type B plugs are found on devices. It is always downstream. A USB device is detected by the host, if any of the lines D+ or D- are pulled up through a resistor. A full speed device pulls up the D+ pin through a resistor to 3.5V. A low speed device pulls up the D- pin through a resistor to 3.5V. The figure will explain the statement. Figure (1);
There are three classes of USB functions;- Low-power bus powered functions – It is draw the power from the V bus and cannot draw any more than one unit load.
- High-power bus powered functions - It is draw the power from the bus and cannot draw more than one unit load until it has been configured
- Self-powered functions -These may draw up to 1unit load from the bus and derive the rest of its power from an external source.
For all schematic circuit is shows the figure;
