DSP

应用定时器，通过应用程序控制LED闪灭（linux设备驱动程序学习）

2019-07-13 19:45发布

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驱动程序源代码：led_timer.c
#include #include #include #include #include #include #include #include static volatile unsigned int *GPJ2CON,*GPJ2DAT; static int major = 0; struct timer_list time; static int counter; static void led(unsigned long arg)//定时器处理函数 { *GPJ2DAT &= 0xf0; mdelay(500); *GPJ2DAT |= 0x0f; printk(KERN_NOTICE "current jiffies is %ld ",jiffies); counter++; mod_timer(&time,jiffies + HZ); //修改定时时间 } static int led_open(struct inode *pi, struct file *pf) { printk("test open. "); *GPJ2CON &= 0xffff0000; *GPJ2CON |= 0x00001111; //设置为输出 *GPJ2DAT |= 0x0f; //熄灭所有LED counter = 0; init_timer(&time);//初始化定时器 time.function = &led; time.expires = jiffies + HZ; /* HZ = 1S jiffies_to_msecs(1000) = 3906 jiffies_to_msecs(10000) = 39062 msecs_to_jiffies(1000) = 256 */ add_timer(&time);//添加，启动定时器 return 0; } static int led_release(struct inode *pi, struct file *pf) { del_timer(&time); printk(" test release. "); return 0; } static ssize_t led_read(struct file *pf, char __user *pbuf, size_t len, loff_t *ppos) { put_user(counter,(int *)pbuf); return 0; } static struct file_operations led_fops = { .owner = THIS_MODULE, .open = led_open, .release = led_release, .read = led_read, }; static __init int led_init(void) { major = register_chrdev(0, "LED", &led_fops); printk("major = %d ",major); GPJ2CON = ioremap(0xe0200280, 8); GPJ2DAT = GPJ2CON + 1; return 0; } static __exit void led_exit(void) { iounmap(GPJ2CON); unregister_chrdev(major, "LED"); *GPJ2DAT |= 0x0f; printk(" Goodbye! "); } module_init(led_init); module_exit(led_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Huang Dezhi"); MODULE_DESCRIPTION("This is LED TIMER");
在kernel/drivers/char下的Kconfig里面添加 config LED_TIMER 
        tristate "LED TIMER"
        default y
在kernel/drivers/char下的Makefile里面添加
obj-m       += led-timer.o
在kernel下编译：$ make menuconfig                            $ make modules

应用程序：led_timer_app.c
#include #include #include #include #include #include #include int main() { int fd; int counter = 0; int count ; char buf[4]; fgets(buf,sizeof(buf),stdin); count = atoi(buf); fd = open("led",O_RDWR); /*打开second设备文件*/ if(fd != -1) { while( (count -1) >= counter ) { read(fd,&counter,sizeof(unsigned int));//读目前经历的秒数 } } else { printf("Device open failure "); } return 0; }
下载到开发板上：tftp -g -r led_timer.ko 192.168.x.x                            tftp -g -r led_timer_app 192.168.x.x 修改led_timer_app 的权限: chmod 777 led_timer_app 装载模块：insmod led_timer.ko 创建设备：mknod led c 251 0 执行程序：./led_timer_app
然后输入数字会看到LED闪亮指定次数

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