驱动开发-定时中断技术

1、定时中断技术一、 确定任务1、 掌握基本的字符设备的驱动程序设计。2、 掌握基本的文件操作。3、 掌握在操作系统下的定时器驱动程序的原理。二、 学习内容 1、 阅读S5PV210数据手册，熟悉计数器的原理。2、 编写定时中断的应用程序。3、 编写makefile文件。4、掌握ARM定时中断驱动程序的基本框架结构。三、基础知识1、 硬件原理：a) 原理图：（略）b) 系统框架图：由该图可知，在选取了PCLK作为时钟源后，需经过8BIT PRESCALER0分频器，而后，经过1/1或1/2或1/4或1/8或1/16分频器后，送到逻辑控制电路（Control LogicX）后，被送到引脚输出。所以，

2、对PWM的操作就是围绕设置时钟分频，得到合适的频率，然后，设置逻辑控制电路得到合适的脉宽。c) 寄存器简介：寄存器TCFG0用于配置PWM的预分频比，TCFG015：8八位用于配置计时器2、3、4（timer2、timer3、timer4）的预分频值。TCFG07:0八位用于配置计时器0、1的预分频值。寄存器TCFG1用于配置PWM的分频比。PWM控制寄存器TCON，设置启动PWM，装载寄存器，输出反相及寄存器自动装载等功能。TCNTB0是timer0的定时器计数寄存器（其他定时计数器功能类似这里不再赘述）。TCMPB0是timer0的定时器比较寄存器。TCNTO0是timer0的定时器计数观

3、察寄存器，可以从中读出当前计数寄存器中的值。TINT_CSTAT是定时器的中断使能控制器和中断状态寄存器。四、代码设计 1、 PWM输出的原理：PWM输出脚，默认为低电平，PWM计数器TCNTn的初始值等于TCNTBn，当TCNTn的值递减到等于TCMPBn的值时，PWM输出高电平，当PWM计数器的递减到0时，输出又变为低电平，如此周而复始。2、 驱动原理：该驱动实现为一个字符设备，通过ioctl函数来设置相关寄存器的值，以此来实现PWM波形的输出与禁止3、 驱动代码分析：（详细代码请查看附件）#define DEVICE_NAME "timer"#define DEVIC

4、E_ID1static atomic_ton; static irqreturn_t led_on_off(int irq , void *dev_id) /timer中断服务程序if(on.counter) /根据原子量的不同值设置led灯的亮和灭gpio_set_value(S5PV210_GPJ2(0),on.counter&0xf); atomic_dec(&on); else gpio_set_value(S5PV210_GPJ2(0),on.counter&0xf);atomic_inc(&on);return IRQ_HANDLED;static

5、void pwm_stop(void)unsigned long flags;unsigned long tcon;spin_lock_irqsave(&pwm_spin_lock, flags);tcon = _raw_readl(S3C2410_TCON);tcon &= (1<<(TCON_BASE+0); / S3C2410_TCON_T1START 停止timer_raw_writel(tcon, S3C2410_TCON);spin_unlock_irqrestore(&pwm_spin_lock, flags);static void pwm_

6、set_freq(unsigned long freq) tcon = _raw_readl(S3C2410_TCON); tcfg1 = _raw_readl(S3C2410_TCFG1); tcfg0 = _raw_readl(S3C2410_TCFG0); tcon &= S3C2410_TCON_T1START; /stop timer1 _raw_writel(tcon,S3C2410_TCON); tcfg0 &= S3C2410_TCFG_PRESCALER0_MASK;tcfg0 |= (255 - 1); tcfg1 &= S3C2410_TCFG1_

7、MUX1_MASK; tcfg1 |= S3C2410_TCFG1_MUX1_DIV2; _raw_writel(tcfg1, S3C2410_TCFG1); /设置分频值 _raw_writel(tcfg0, S3C2410_TCFG0); /设置预分频值 clk_p = clk_get(NULL, "pclk"); pclk = clk_get_rate(clk_p);/tcnt = (pclk/(tcfg0+1)/16)*freq; _raw_writel(tcnt, S3C2410_TCNTB(DEVICE_ID); /设置TCNT计数值_raw_writel(tc

8、nt/2,S3C2410_TCMPB(DEVICE_ID); /设置TCMP比较值 tcon |=S3C2410_TCON_T1RELOAD|S3C2410_TCON_T1MANUALUPD; /自动加载和手动更新 _raw_writel(tcon, S3C2410_TCON);tcon &=S3C2410_TCON_T1INVERT;/电平不反转_raw_writel(tcon,S3C2410_TCON); tcon |=S3C2410_TCON_T1RELOAD;tcon &=(S3C2410_TCON_T1MANUALUPD); /自动加载和禁止手动更新 _raw_wri

9、tel(tcon,S3C2410_TCON);tint = _raw_readl(S3C64XX_TINT_CSTAT); tint |= (0x1<<1); _raw_writel(tint,S3C64XX_TINT_CSTAT); /timer中断使能 tcon |=S3C2410_TCON_T1START; _raw_writel(tcon, S3C2410_TCON); /启动计时器static int gec210_pwm_open(struct inode *inode, struct file *file) ret = request_irq(IRQ_TIMER1,l

10、ed_on_off,IRQF_TIMER,DEVICE_NAME,"timer2"); /申请时钟中断。static int gec210_pwm_close(struct inode *inode, struct file *file)pwm_stop();/停止计时器。up(&lock);free_irq(IRQ_TIMER1,"timer2"); /释放timer中断return 0;static int gec210_pwm_ioctl(struct inode *inode, struct file *file, unsigned in

11、t cmd, unsigned long arg)switch (cmd) case PWM_IOCTL_SET_FREQ: pwm_set_freq(arg); /设置计数值case PWM_IOCTL_STOP:pwm_stop(); / 停止计数器return 0;static ssize_t gec210_pwm_read (struct file *filp, char _user *buff, size_t count, loff_t *offp)cnt = _raw_readl(S3C2410_TCNTB(DEVICE_ID); /计数初始值printk("TCNTB

12、: t%ldn",cnt);cnt = _raw_readl(S3C2410_TCNTO(DEVICE_ID);/计数实时值printk("TCNTO %ldn",cnt);ret = copy_to_user(buff,&cnt,count); /返回实时值到用户空间return ret ;static struct file_operations dev_fops = /操作方法.owner = THIS_MODULE,.open = gec210_pwm_open,.release = gec210_pwm_close, .ioctl = gec21

13、0_pwm_ioctl,.read = gec210_pwm_read,;static struct miscdevice misc = /misc设备结构.minor = MISC_DYNAMIC_MINOR,.name = DEVICE_NAME,.fops = &dev_fops,;static int _init dev_init(void)init_MUTEX(&lock);/初始化信号锁 s3c_gpio_cfgpin(S5PV210_GPJ2(0), S3C_GPIO_OUTPUT); /设置led灯ret = misc_register(&misc);

14、/注册misc设备static void _exit dev_exit(void)misc_deregister(&misc); /注销misc设备module_init(dev_init);module_exit(dev_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("GEC Inc.");MODULE_DESCRIPTION("S5PV210/S3C2410/S3C2440 PWM Driver");4、 驱动程序makefile请参照蜂鸣器实验编写。5、 测试程序和蜂鸣器大致相同，这

15、里不再分析。本实验设置预分频值255、分频值采用默认值1。通过执行测试程序最低可实现约0.03秒产生一次定时中断，例如./timer_irq_test on 2 约0.06秒的将产生一次中断。#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

16、.h>#include <sys/time.h>#include <errno.h>#include <limits.h>#define PWM_IOCTL_SET_FREQ 1#define PWM_IOCTL_STOP 0 void Usage(char *args)printf("Usage: %s <on/off> <freq>n",args);return ;int main(int argc , char *argv)int buzzer_fd;unsigned long freq;char *e

17、ndstr, *str;unsigned long counter=0;int ret ;if(argc=3)buzzer_fd = open("/dev/timer",O_RDWR); /注意： 打开设备为timer if(buzzer_fd<0)perror("open device:");exit(1);str = argv2;errno = 0;freq = strtol(str , &endstr, 0);if(errno = ERANGE &&(freq = LONG_MAX |freq =LONG_MIN)|(

18、errno !=0 && freq =0)perror("freq :");exit(EXIT_FAILURE);if(endstr =str)fprintf(stderr , "Please input a digits for freqn");exit(EXIT_FAILURE);if(!strncmp(argv1, "on" ,2)ioctl(buzzer_fd, PWM_IOCTL_SET_FREQ , freq );else if(!strncmp(argv1, "off", 3)ioct

19、l(buzzer_fd , PWM_IOCTL_STOP , freq);elseclose(buzzer_fd);exit(EXIT_FAILURE);else if(argc =2)buzzer_fd = open("/dev/timer",O_RDWR);if(buzzer_fd<0)perror("open device:");exit(1);if(!strncmp(argv1, "off", 3)ioctl(buzzer_fd , PWM_IOCTL_STOP , freq); /此处freq并无实际作用elseclose(buzzer_fd);exit(EXIT_FAILURE);else Usage(argv0);exit(EXIT_FAILURE);while(1)#if 0ret = read(buzzer_fd,&counter,sizeof(counter); /读取驱动传上来的TCNTO值if(ret <0)perror("read");exit(EXIT_FAILURE);printf("counter %dn",counter);#end