Electronics-project-design.com has a background of what USB is and does as well as a reference project to check out – “The following USB2.0 reference project from Freescale Semiconductor describes in detailed the design of a USB2.0 Card Reader. It support cards such as Compactflash, Memory Stick, Memory Stick Duo, Magic Gate, Secure Digital, MultimediaCard and SmartMedia. The schematic and source code of the reference projects are provided. This project is a good reference for students who need to do an electronics project in their final year of studies.” – Link & Universal serial bus card reader.
USB circuit design