Universal Serial Bus Interface

The prox card reader connects to a computer using a USB interface. USB is extensively and exhaustively documented elsewhere (see the Resources page), so we won't dedicate much to it here.

The microcontroller used in our design, the PIC16C745, has integrated USB functionality. We implemented this using the standard design described in the datasheet.

The prox card reader operates as a self-powered, low power device, meaning that it draws all its power from the host USB port and can draw a maximum of 100mA at 5V. For our purposes, this is more than sufficient.

The reader enumerates as a HID compliant keyboard, since it is sufficient for our low data rate and gives us excellent compatabilty with any USB-enabled host without needing driver software.