USB Embedded Host Stack Programmer's Guide

AN1141 USB Embedded Host Stack Programmer's Guide FEATURES Author: Bud Caldwell Microchip Technology Inc. * Supports USB embedded host applications * Handles device enumeration and configuration * Supports multiple class or "client" drivers INTRODUCTION * Support for hosting multi-function devices The Universal Serial Bus (USB) provides a common * Support for root-port power control interface that greatly simplifies how an end user con- * Provides a simple Application Program Interface nects many types of peripheral devices to a personal (API) computer (PC). Beyond just the PC, many embedded * Provides a simple Client Driver Interface (CDI) systems can take advantage of the USB as a way to connect to a wide variety of peripherals. * Uses a table-driven method to implement the host's Targeted Peripheral List (TPL) Unlike a PC, an embedded host is only required to sup- * Support for control, interrupt, bulk, and port a predefined set of peripherals. Microchip provides isochronous transfers. sample firmware that enables hosts, using supported Microchip microcontrollers, to control some of the most commonly requested types of USB peripheral devices LIMITATIONS (see "References"). * Does not support hubs For cases in which host firmware is not available to * Supports a single USB root port control the type of device required, the Microchip USB * Number of client drivers supported limited only by embedded host firmware stack provides an easy-to- available memoryuse framework that simplifies the development of USB 2.0 compliant embedded hosts. This application note describes how to implement a SYSTEM HARDWARE "client" driver for a USB peripheral using the Microchip The USB firmware stack was developed for the host framework. Use of this framework simplifies imple- following hardware: mentation of firmware for an embedded host and makes it much easier to control almost any type of USB variants of the PIC24 and PIC32 families of peripheral device desired. microcontrollers. ASSUMPTIONS * Working knowledge of C programming language * Familiarity with the USB 2.0 protocol * Familiarity with the USB class or device to be hosted. ® IDE* Familiarity with Microchip MPLAB