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#!/bin/sh<br>base=led-player //定义一个变量方便引用led-player程序<br># See how we were called.case "$1" in
//开关机时传递的参数，开机为start，关机为stop start) /usr/bin/$base
& //开机运行该脚本时自动运行led-player于后台 ;; stop) //关机运行该脚本时终止led-player进程 pid=`/bin/pidof $base` //获取led-player进程号(反引号在shell中表示执行命令) if
[ -n "$pid"
]; then //若字符长度非0，则执行kill -9 pid（led-player进程号） kill -9 $pid fi ;;esacexit 0 |
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#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/ioctl.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <sys/select.h>#include <sys/time.h>#include <string.h>static
int led_fd; //静态变量，没有初始化则默认为0static
int type = 1;static
void push_leds(void){ static
unsigned step; unsigned led_bitmap; int
i; switch(type) { case
0: //当type变量值为0时，实现循环流水灯效果，即1-2-3-4-3-2-1如此循环 if
(step >= 6) { step = 0; } if
(step < 3) { led_bitmap = 1 << step; } else
{ led_bitmap = 1 << (6 - step); } break; case
1: /*默认type变量值为1，实现累加器功能，即0000-0001-0010-0011-0100-0101...依次累加（1表示灯亮）*/ if
(step > 255) { step = 0; } led_bitmap = step; //此时led_bitmap为8位二进制数 break; default: led_bitmap = 0; } step++; //每次调用执行本函数则step自加1 for
(i = 0; i < 4; i++) { ioctl(led_fd, led_bitmap & 1, i); //控制leds设备，分四次写入相应的值，估计i是写入驱动设备的位置参数 led_bitmap >>= 1; }}int
main(void){ int
led_control_pipe; int
null_writer_fd; // for read endpoint not blocking when control process exit double
period = 0.5; led_fd = open("/dev/leds0", 0); //以只读方式打开设备leds0 if
(led_fd < 0) { led_fd = open("/dev/leds", 0); //mini2440开发板上的是这个设备 } if
(led_fd < 0) { perror("open device leds"); exit(1); } unlink("/tmp/led-control"); //删除指定文件 mkfifo("/tmp/led-control", 0666); //创建指定命名管道文件，权限为0666（首位0表示这个数为八进制数） led_control_pipe = open("/tmp/led-control", O_RDONLY | O_NONBLOCK); if
(led_control_pipe < 0) { perror("open control pipe for read"); exit(1); } null_writer_fd = open("/tmp/led-control", O_WRONLY | O_NONBLOCK); if
(null_writer_fd < 0) { perror("open control pipe for write"); exit(1); } for
(;;) { fd_set rds; struct
timeval step; int
ret; FD_ZERO(&rds); //将rds描述符集清零 FD_SET(led_control_pipe, &rds); //将rds描述符集中描述符led_control_pipe对应的位置1 step.tv_sec = period; step.tv_usec = (period - step.tv_sec) * 1000000L; ret = select(led_control_pipe + 1, &rds, NULL, NULL, &step); //只关心readfds描述符集，其他两个为NULL if
(ret < 0) { perror("select"); exit(1); } if
(ret == 0) { //指定等待时间已超过而指定的描述符还没准备好 push_leds(); } else
if (FD_ISSET(led_control_pipe, &rds)) { static
char buffer[200]; for
(;;) { char
c; int
len = strlen(buffer); if
(len >= sizeof
buffer - 1) { memset(buffer, 0, sizeof
buffer); //对buffer数组初始化 break; } if
(read(led_control_pipe, &c, 1) != 1) { //从命名管道文件led-control中读取一个字节 break; } if
(c == ‘\r‘) { //读出字符为回车符，则忽略后面的语句，重新循环 continue; } if
(c == ‘\n‘) { //读出字符为换行符 int
tmp_type; double
tmp_period; if
(sscanf(buffer,"%d%lf", &tmp_type, &tmp_period) == 2) { type = tmp_type; period = tmp_period; } fprintf(stderr, "type is %d, period is %lf\n", type, period); //将参数type、period输出到终端显示 memset(buffer, 0, sizeof
buffer); //成功取完一次参数，将buffer数组清零 break; } buffer[len] = c; //将读到的字符写入buffer数组（前面的程序已经实现舍弃回车符和换行符） } } } close(led_fd); //关掉leds设备 return
0;} |
mini2440应用例程学习（一）—— led-player,布布扣,bubuko.com
mini2440应用例程学习（一）—— led-player
原文：http://www.cnblogs.com/11hwu2/p/3714967.html