Simple PIC USB Interface

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USB Theory: USB Host - Managing USB Devices

           The main job of the USB host is to offer and control a pathway for devices to communicate to it. This means a host must keep track of which devices are connected, what type of devices they are, and how much communication bandwidth they need and can receive. Therefore, the USB host controls the device priority and flow of information making a the gate-keeper of the USB communication protocol.

Host->Device Communication

           The USB protocol has a specific set of guidelines for how the USB host should communicate with devices. At a high level, the host is constantly polling devices for their current status. A USB device cannot initiate the communication, that is the job of the USB host. Since the USB Host must control and do so many things at the same time, a USB memory buffers/stack is necessary.