原文地址::http://blog.csdn.net/midion9/article/details/49862991
| 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173 | /*===========================================*《linux声音设备编程实例》* 1. 对内部扬声器编程*  内部扬声器是控制台的一部分,所以它对应的设备文件为/dev/console。*    变量KIOCSOUND在头文件 /usr /include /linux /kd.h中声明,*    ioctl函数使用它可以来控制扬声器的发声,使用规则为:*      ioctl ( fd, KIOCSOUND, (int) tone);*      fd为文件设备号,tone 是音频值。当tone为0时,终止发声。*    必须一提的是它所理解的音频和我们平常以为的音频是不同的,*    由于计算机主板定时器的时钟频率为1.19MHZ,所以要进行正确的发声,*    必须进行如下的转换:*  扬声器音频值=1190000/我们期望的音频值。*  扬声器发声时间的长短我们通过函数usleep(unsigned long usec)来控制。*    它是在头文件/usr /include /unistd.h中定义的,让程序睡眠usec微秒。*    下面即是让扬声器按指定的长度和音频发声的程序的完整清单:*========================================================*/#include <fcntl.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/ioctl.h>#include <sys/types.h>#include <linux/kd.h>/* 设定默认值 */#define DEFAULT_FREQ 440   /* 设定一个合适的频率 */#define DEFAULT_LENGTH 200 /* 200 微秒,发声的长度是以微秒为单位的*/#define DEFAULT_REPS 1     /* 默认不重复发声 */#define DEFAULT_DELAY 100  /* 同样以微秒为单位*//* 定义一个结构,存储所需的数据*/typedefstruct{    intfreq;   /* 我们期望输出的频率,单位为Hz */    intlength; /* 发声长度,以微秒为单位*/    intreps;   /* 重复的次数*/    intdelay;  /* 两次发声间隔,以微秒为单位*/} beep_parms_t;/* 打印帮助信息并退出*/voidusage_bail ( constchar*executable_name ) {    PRintf( "Usage: /n /t%s [-f frequency] [-l length] [-r reps] [-d delay] /n ",    executable_name );    exit(1);}/*===================================* 分析运行参数,各项意义如下:* "-f <以HZ为单位的频率值 >"* "-l <以毫秒为单位的发声时长 >"* "-r <重复次数 >"* "-d <以毫秒为单位的间歇时长 >"* =====================================*/voidparse_command_line(char**argv, beep_parms_t *result) {    char*arg0 = *(argv++);    while( *argv ) {        if( !strcmp( *argv,"-f")) { /*频率*/            intfreq = atoi( *( ++argv ) );            if( ( freq <= 0 ) || ( freq > 10000 ) ) {                fprintf( stderr, "Bad parameter: frequency must be from 1..10000/n");                exit(1) ;            } else{                result->freq = freq;                argv++;            }        } elseif( ! strcmp( *argv, "-l") ) { /*时长*/            intlength = atoi( *(++argv ) );            if(length < 0) {                fprintf(stderr, "Bad parameter: length must be >= 0/n");                exit(1);            } else{                result->length = length;                argv++;            }        } elseif(!strcmp(*argv, "-r")) { /*重复次数*/            intreps = atoi(*(++argv));            if(reps < 0) {                fprintf(stderr, "Bad parameter: reps must be >= 0/n");                exit(1);            } else{                result->reps = reps;                argv++;            }        } elseif(!strcmp(*argv, "-d")) { /* 延时 */            intdelay = atoi(*(++argv));            if(delay < 0) {                fprintf(stderr, "Bad parameter: delay must be >= 0/n");                exit(1);            } else{                result->delay = delay;                argv++;            }        } else{            fprintf(stderr, "Bad parameter: %s/n", *argv);            usage_bail(arg0);        }    }}intmain(intargc, char**argv) {    intconsole_fd;    inti; /* 循环计数器 */    /* 设发声参数为默认值*/    beep_parms_t parms = {DEFAULT_FREQ, DEFAULT_LENGTH, DEFAULT_REPS,    DEFAULT_DELAY};    /* 分析参数,可能的话更新发声参数*/    parse_command_line(argv, &parms);    /* 打开控制台,失败则结束程序*/    if( ( console_fd = open ( "/dev/console", O_WRONLY ) ) == -1 ) {        fprintf(stderr, "Failed to open console./n");        perror("open");        exit(1);    }    /* 真正开始让扬声器发声*/    for(i = 0; i < parms.reps; i++) {        /* 数字1190000从何而来,不得而知*/        intmagical_fairy_number = 1190000/parms.freq;        ioctl(console_fd, KIOCSOUND, magical_fairy_number); /* 开始发声 */        usleep(1000*parms.length);       /*等待... */        ioctl(console_fd, KIOCSOUND, 0); /* 停止发声*/        usleep(1000*parms.delay);        /* 等待... */    } /* 重复播放*/    returnEXIT_SUCCESS;} | 
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