Nut/OS API

This sample application plays MP3 files from the UROM filesystem. It demonstrates how to use the global segmented buffer and the MP3 decoder driver and can provide a basis for talking equipment, alarm sound output etc.
The UROM filesystem is located in the CPU's flash ROM. No external file storage device is required. Use the crurom utility to create a C source file named urom.c from the MP3 files located in subdirectory sounds. Here's how to call crurom:
/*
 * Copyright (C) 2003-2006 by egnite Software GmbH. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY EGNITE SOFTWARE GMBH AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL EGNITE
 * SOFTWARE GMBH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * For additional information see http://www.ethernut.de/
 *
 */

#include <dev/board.h>
#include <dev/vs1001k.h>
#include <dev/debug.h>
#include <dev/urom.h>

#include <sys/version.h>
#include <sys/heap.h>
#include <sys/event.h>
#include <sys/timer.h>
#include <sys/thread.h>
#include <sys/bankmem.h>

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <io.h>
#include <fcntl.h>
#include <errno.h>

static int PlayMp3File(char *path);

int main(void)
{
    /* Baudrate for debug output. */
    u_long baud = 115200;

    /*
     * Register our devices.
     */
    NutRegisterDevice(&devUrom, 0, 0);
    NutRegisterDevice(&DEV_DEBUG, 0, 0);

    /*
     * Assign stdout to the debug device.
     */
    freopen(DEV_DEBUG_NAME, "w", stdout);
    _ioctl(_fileno(stdout), UART_SETSPEED, &baud);

    /*
     * Print a banner.
     */
    printf("\n\nPlay MP3 files on Nut/OS %s\n", NutVersionString());

#if defined(__AVR__)

    /*
     * Initialize the MP3 buffer. The NutSegBuf routines provide a global
     * system buffer, which works with banked and non-banked systems.
     */
    if (NutSegBufInit(8192) == 0) {
        puts("NutSegBufInit: Fatal error");
    }

    /* 
     * Initialize the MP3 decoder hardware.
     */
    if (VsPlayerInit() || VsPlayerReset(0)) {
        puts("VsPlayer: Fatal error");
    }

    /*
     * Play the MP3 files in an endless loop. For each file set the volume 
     * of the left and right channel, call the local routine PlayMp3File() 
     * and sleep one second before playing the next sound file.
     */
    for (;;) {
        VsSetVolume(0, 254);
        PlayMp3File("UROM:sound1a.mp3");
        NutSleep(1000);

        VsSetVolume(0, 0);
        PlayMp3File("UROM:sound2a.mp3");
        NutSleep(1000);

        VsSetVolume(254, 0);
        PlayMp3File("UROM:sound3a.mp3");
        NutSleep(1000);

        VsSetVolume(0, 0);
        PlayMp3File("UROM:sound4a.mp3");
        NutSleep(1000);
    }
#else /* !__AVR__ */
    for (;;);
#endif /* !__AVR__ */
}

#if defined(__AVR__)

/*
 * Play MP3 file from local file system.
 *
 * \param path Pathname of the MP3 file to play.
 *
 * \return 0 on success, -1 if opening the file failed.
 */
static int PlayMp3File(char *path)
{
    int fd;
    size_t rbytes;
    u_char *mp3buf;
    int got;
    u_char ief;

    /*
     * Open the MP3 file.
     */
    printf("Play %s: ", path);
    if ((fd = _open(path, _O_RDONLY | _O_BINARY)) == -1) {
        printf("Error %d\n", errno);
        return -1;
    }
    puts("OK");

    /* 
     * Reset decoder buffer.
     */
    printf("[B.RST]");
    ief = VsPlayerInterrupts(0);
    NutSegBufReset();
    VsPlayerInterrupts(ief);

    for (;;) {
        /*
         * Query number of byte available in MP3 buffer.
         */
        ief = VsPlayerInterrupts(0);
        mp3buf = NutSegBufWriteRequest(&rbytes);
        VsPlayerInterrupts(ief);

        /* 
         * Read data directly into the MP3 buffer. 
         */
        if (rbytes) {
            printf("[B.RD%d]", rbytes);
            if ((got = _read(fd, mp3buf, rbytes)) > 0) {
                printf("[B.CMT%d]", got);
                ief = VsPlayerInterrupts(0);
                mp3buf = NutSegBufWriteCommit(got);
                VsPlayerInterrupts(ief);
            } else {
                printf("[EOF]");
                break;
            }
        }

        /*
         * If the player is not running, kick it.
         */
        if (VsGetStatus() != VS_STATUS_RUNNING) {
            printf("[P.KICK]");
            VsPlayerKick();
        }

        /*
         * Allow background threads to take over.
         */
        NutThreadYield();
    }

    _close(fd);

    /* 
     * Flush decoder and wait until finished. 
     */
    printf("[P.FLUSH]");
    VsPlayerFlush();
    while (VsGetStatus() != VS_STATUS_EMPTY) {
        NutSleep(1);
    }

    /*
     * Reset the decoder. 
     */
    printf("[P.RST]");
    VsPlayerReset(0);

    printf("\nDone, %u bytes free\n", NutHeapAvailable());
    return 0;
}

#endif /* !__AVR__ */
playmp3/playmp3.c
