How is data transferred in USB protocol?
USB Specification defines four different types of data transfers mechanisms. Control Transfer The USB Host sends commands & query to USB device using Control transfer. The Control transfer uses End point 0(EP0) while USB device is being enumerated and thus it is mandatory to support EP0 by all USB device irrespective of supported speed. The maximum size for a Control packet is 8, 16, 32 or 64 bytes. The packet length of Control transfer in Low-speed USB device must be 8Bytes, for Full-speed USB device must be 64Bytes and for High-speed USB device allows 8, 16, 32 or 64Bytes. Interrupt Transfer Interrupt transfers are a method for a USB device to request a certain polling rate from the USB host. The polling time is requested to USB Host by USB device during enumeration process. The maximum polling rate for a full-speed device is once per millisecond and once per every 10 milliseconds on low speed devices. The maximum data payload size for Low-speed USB device is 8Bytes, for Full-speed U
