基于DE2的MP3音乐播放器

/************************************************************************** * Copyright � 2004 Altera Corporation, San Jose, California, USA. * * All rights reserved. All use of this software and documentation is * * subject to the License Agreement located at the end of this file below.* *************************************************************************/ /****************************************************************************** * DANGER ** WARNING ** Please read before proceeding! ** WARNING ** DANGER * ****************************************************************************** * * This program is an example of a "free-standing" C application. If you * modify this example and try to call C library functions such as printf, they * will NOT work unless you explicitly initialize the system, such as in the * hello_alt_main software template. Please see below for details. * * Description * ************* * A very minimal program that simply shifts an LED back and forth. * * Requirements * ************** * According to the ANSI C standard, freestanding programs "own" the hardware, * and cannot rely on system-services or device-drivers being initialized prior * to program-start. A freestanding program is responsible for initializing all * hardware devices, device-drivers, and system-services. Many embedded * programs are, by nature, freestanding. The author relinquishes any illusion * of running their program on a workstation. * * This example is a freestanding program because it's entry point is the * function: * * void alt_main (void) * * As opposed to "main()" as a "hosted" application would (see the * "hello_world" example). * * Upon entry to alt_main(): * - The CPU's caches (if any) have been initialized. * - The stack-pointer has been set. * - That's all. The rest is up to you. * * If you modify this example and try to call C library functions such as * printf, they will NOT work unless you explicitly initialize the system. * If you wish to use C library calls, it is strongly suggested you start * with the hosted hello_world template which uses main() as it's entry * point. * * On the other hand, if you want to write a program that gets-in even * earlier, you will need to provide your own assembly-language machine-setup * code by defining the symbol "_start". Any definition of _start in your * directory will override the library definition. You can find source code * for the Nios II library _start here: * * <NiosII-Kit-Install-Dir>/components/altera_nios2/HAL/src/crt0.S * * This software example requires a system with a PIO peripheral named * "led_pio". The software example will run on the following hardware * examples: * * Nios Development Board, Stratix II Edition: * - Standard * - Small * - Full Featured * * DSP Development Board, Stratix II Edition: * - Standard * - Small * - Full Featured * * Nios Development Board, Stratix Edition: * - Standard * - Small * - Full Featured * * Nios Development Board, Stratix Professional Edition: * - Standard * - Small * - Full Featured * * Nios Development Board, Cyclone Edition: * - Standard * - Small * - Low Cost * - Full Featured * * Peripherals Exercised by SW * ***************************** * The hello_led.c program simply shifts an 8-bit variable back and forth, * writing the variable's value to the system's LED PIO peripheral on every * iteration. * * Software Files * **************** * hello_led.c - Main C file that contains the simple led manipulation routine. * */