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嵌入式ARM Linux一般使用pwm来控制液晶屏LCD的背光亮度，所以背光的调节就是控制pwm。
方法一，命令控制
查看当前背光亮度：
[mw_shl_code=bash,true]cat /sys/class/backlight/backlight/brightness[/mw_shl_code]
设置背光亮度：
[mw_shl_code=bash,true]echo 100 > /sys/class/backlight/backlight/brightness [/mw_shl_code]
方法二，应用程序
[mw_shl_code=c,true]#include <fcntl.h>
#include <sys/ioctl.h>
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
int fd;
int tmp;
char light[4];
fd = open("/sys/class/backlight/backlight/brightness", O_RDWR);
if (fd < 0) {
perror("Open brightness error");
return 1;
}
while (1) {
scanf("%3s", light);
light[3] = '\0';
if (write(fd, light, strlen(light)) < 0) {
perror("Writing occur error");
}
}
return 0;
}
[/mw_shl_code]
将以上程序编译，然后把生成的 pwm_lcd 镜像拷贝到开发板，执行：
[mw_shl_code=bash,true]chmod +x pwm_lcd
./pwm_lcd[/mw_shl_code]
代码下载和镜像下载：
pwm_lcd_brightness.zip
(5.04 KB, 下载次数: 10923)
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