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【玩转VLC】--- ubuntu下编译vlc
1.安装vlc依赖的库

    

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Phone 通话界面屏幕长亮

    

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MINI2440开发板PWM驱动与测试程序简要分析

先看下电路原理图

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/fs.h>

#include <linux/init.h>

#include <linux/delay.h>

#include <linux/poll.h>

#include <linux/interrupt.h>

#include <linux/gpio.h>

 

#include <asm/irq.h>

#include <asm/io.h>

#include <asm/uaccess.h>

#include <mach/regs-gpio.h>

#include <mach/hardware.h>

#include <plat/regs-timer.h>

#include <mach/regs-irq.h>

#include <asm/mach/time.h>

#include <linux/clk.h>

#include <linux/cdev.h>

#include <linux/device.h>

#include <linux/miscdevice.h>

 

#define DEVICE_NAME     "pwm"

 

#define PWM_IOCTL_SET_FREQ              1    //设置pwm的频率

#define PWM_IOCTL_STOP                        0    //停止pwm

 

static struct semaphore lock;            

//定义信号量，此处的信号量是一个互斥信号量，用于PWM设备之多只能被一个进程打开

 

/* freq:  pclk/50/16/65536 ~ pclk/50/16

  * if pclk = 50MHz, freq is 1Hz to 62500Hz

  * human ear : 20Hz~ 20000Hz

  */

static void PWM_Set_Freq( unsigned long freq )

{

         unsigned long tcon;

         unsigned long tcnt;

         unsigned long tcfg1;

         unsigned long tcfg0;

 

         struct clk *clk_p;

         unsigned long pclk;

 

         //set GPB0 as tout0, pwm output

         s3c2410_gpio_cfgpin(S3C2410_GPB(0), S3C2410_GPB0_TOUT0);//功能配置

 

         tcon = __raw_readl(S3C2410_TCON);    //获得定时器控制寄存器的数值

         tcfg1 = __raw_readl(S3C2410_TCFG1);   //获得定时器配置寄存器0的值

         tcfg0 = __raw_readl(S3C2410_TCFG0);   //获得定时器配置寄存器1的值

 

         //prescaler = 50

         tcfg0 &= ~S3C2410_TCFG_PRESCALER0_MASK;

         tcfg0 |= (50 - 1);

 

         //mux = 1/16

         tcfg1 &= ~S3C2410_TCFG1_MUX0_MASK;

         tcfg1 |= S3C2410_TCFG1_MUX0_DIV16;

 

         __raw_writel(tcfg1, S3C2410_TCFG1);

         __raw_writel(tcfg0, S3C2410_TCFG0);

 

         clk_p = clk_get(NULL, "pclk");

         pclk  = clk_get_rate(clk_p);

         tcnt  = (pclk/50/16)/freq;

        

         __raw_writel(tcnt, S3C2410_TCNTB(0));

         __raw_writel(tcnt/2, S3C2410_TCMPB(0));

                                    

         tcon &= ~0x1f;

         tcon |= 0xb;               //disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 0

         __raw_writel(tcon, S3C2410_TCON);

        

         tcon &= ~2;                         //clear manual update bit

         __raw_writel(tcon, S3C2410_TCON);

}

 

static void PWM_Stop(void)

{

         s3c2410_gpio_cfgpin(S3C2410_GPB(0), S3C2410_GPIO_OUTPUT);

         s3c2410_gpio_setpin(S3C2410_GPB(0), 0);

}

 

static int s3c24xx_pwm_open(struct inode *inode, struct file *file)

{

         if (!down_trylock(&lock))//判断是否设备已经打开，已打开返回EBUSY

                   return 0;

         else

                   return -EBUSY;

}

 

 

static int s3c24xx_pwm_close(struct inode *inode, struct file *file)

{

         PWM_Stop();//停止PWM

         up(&lock);//释放信号量

    return 0;

}

 

 

static int s3c24xx_pwm_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)

{

         //printk("ioctl pwm: %x %lx\n", cmd, arg);

         switch (cmd) {

         case PWM_IOCTL_SET_FREQ:

                   if (arg == 0)

                            return -EINVAL;

                   PWM_Set_Freq(arg);

                   break;

 

         case PWM_IOCTL_STOP:

                   PWM_Stop();

                   break;

         }

 

         return 0;

}

 

 

static struct file_operations dev_fops = {

    .owner   =   THIS_MODULE,

    .open    =   s3c24xx_pwm_open,

    .release =   s3c24xx_pwm_close,

    .ioctl   =   s3c24xx_pwm_ioctl,

};

 

static struct miscdevice misc = {

         .minor = MISC_DYNAMIC_MINOR,

         .name = DEVICE_NAME,

         .fops = &dev_fops,

};

 

static int __init dev_init(void)

{

         int ret;

 

         init_MUTEX(&lock);

         ret = misc_register(&misc);

 

         printk (DEVICE_NAME"\tinitialized\n");

             return ret;

}

 

static void __exit dev_exit(void)

{

         misc_deregister(&misc);

}

 

module_init(dev_init);

module_exit(dev_exit);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("FriendlyARM Inc.");

MODULE_DESCRIPTION("S3C2410/S3C2440 PWM Driver");

 

分析，这个程序的结构比较简单，只实现了open(),ioctl(),close()功能，其中最主要的就是ioctl()功能，在ioctl()中最重要的核心函数为static void PWM_Set_Freq( unsigned long freq )；所以说只要分析懂了这个函数，这个驱动也都全懂了。要是做过这个裸机程序的就更简单了。里面出现的一些没分析的，在本博客另一篇LED驱动分析中基本都说过了，不清楚的可以去看那个。

首先分析static void PWM_Set_Freq( unsigned long freq )；

static void PWM_Set_Freq( unsigned long freq )

{

         unsigned long tcon;

         unsigned long tcnt;

         unsigned long tcfg1;

         unsigned long tcfg0;

 

         struct clk *clk_p;

         unsigned long pclk;

 

         //set GPB0 as tout0, pwm output

         s3c2410_gpio_cfgpin(S3C2410_GPB(0), S3C2410_GPB0_TOUT0);//功能配置

 

         tcon = __raw_readl(S3C2410_TCON);    //获得定时器控制寄存器的数值

         tcfg1 = __raw_readl(S3C2410_TCFG1);   //获得定时器配置寄存器0的值

         tcfg0 = __raw_readl(S3C2410_TCFG0);   //获得定时器配置寄存器1的值

 

         //prescaler = 50

         tcfg0 &= ~S3C2410_TCFG_PRESCALER0_MASK;

         tcfg0 |= (50 - 1);

    //上面的两句是设置预分频器

         //mux = 1/16

         tcfg1 &= ~S3C2410_TCFG1_MUX0_MASK;

         tcfg1 |= S3C2410_TCFG1_MUX0_DIV16;

    //上面两句设置MUX0

         __raw_writel(tcfg1, S3C2410_TCFG1);

         __raw_writel(tcfg0, S3C2410_TCFG0);

    //上面两句将配置好的数值写入到配置寄存器

         clk_p = clk_get(NULL, "pclk");

         pclk  = clk_get_rate(clk_p);

    //上面两句用于获取PCLK

         tcnt  = (pclk/50/16)/freq;

         //上面这个数值决定了频率，

         __raw_writel(tcnt, S3C2410_TCNTB(0));

         __raw_writel(tcnt/2, S3C2410_TCMPB(0));

         //上面两句将tcnt寄存器写入到TCNTB0，同时设置S3C2410_TCMPB0，也就是说占空比为50%                       

         tcon &= ~0x1f;    //低五位清零

         tcon |= 0xb;               //disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 0

         __raw_writel(tcon, S3C2410_TCON);

        

         tcon &= ~2;                         //clear manual update bit

         __raw_writel(tcon, S3C2410_TCON);

}

看几个宏定义：

#define S3C2410_TCFG_PRESCALER0_MASK (255<<0)    //0xff<<0

#define S3C2410_TCFG1_MUX0_MASK   (15<<0)       //0xf<<0

#define S3C2410_TCFG1_MUX0_DIV16  (3<<0)       

 

分析：static void PWM_Stop(void)

static void PWM_Stop(void)

{

         s3c2410_gpio_cfgpin(S3C2410_GPB(0), S3C2410_GPIO_OUTPUT);//配置管脚为输出状态

         s3c2410_gpio_setpin(S3C2410_GPB(0), 0);                  //设置管脚为低电平输出

}

 

以下是测试程序

#include <stdio.h>

#include <termios.h>

#include <unistd.h>

#include <stdlib.h>

 

#define PWM_IOCTL_SET_FREQ              1

#define PWM_IOCTL_STOP                        0

 

#define     ESC_KEY            0x1b

 

static int getch(void)

{

         struct termios oldt,newt;

         int ch;

 

         if (!isatty(STDIN_FILENO)) {

                   fprintf(stderr, "this problem should be run at a terminal\n");

                   exit(1);

         }

         // save terminal setting

         if(tcgetattr(STDIN_FILENO, &oldt) < 0) {

                   perror("save the terminal setting");

                   exit(1);

         }

 

         // set terminal as need

         newt = oldt;

         newt.c_lflag &= ~( ICANON | ECHO );

         if(tcsetattr(STDIN_FILENO,TCSANOW, &newt) < 0) {

                   perror("set terminal");

                   exit(1);

         }

 

         ch = getchar();

 

         // restore termial setting

         if(tcsetattr(STDIN_FILENO,TCSANOW,&oldt) < 0) {

                   perror("restore the termial setting");

                   exit(1);

         }

         return ch;

}

 

static int fd = -1;

static void close_buzzer(void);

static void open_buzzer(void)

{

         fd = open("/dev/pwm", 0);

         if (fd < 0) {

                   perror("open pwm_buzzer device");

                   exit(1);

         }

 

         // any function exit call will stop the buzzer

         atexit(close_buzzer);

}

 

static void close_buzzer(void)

{

         if (fd >= 0) {

                   ioctl(fd, PWM_IOCTL_STOP);

                   close(fd);

                   fd = -1;

         }

}

 

static void set_buzzer_freq(int freq)

{

         // this IOCTL command is the key to set frequency

         int ret = ioctl(fd, PWM_IOCTL_SET_FREQ, freq);

         if(ret < 0) {

                   perror("set the frequency of the buzzer");

                   exit(1);

         }

}

static void stop_buzzer(void)

{

         int ret = ioctl(fd, PWM_IOCTL_STOP);

         if(ret < 0) {

                   perror("stop the buzzer");

                  exit(1);

         }

}

 

int main(int argc, char **argv)

{

         int freq = 1000 ;

        

         open_buzzer();

 

         printf( "\nBUZZER TEST ( PWM Control )\n" );

         printf( "Press +/- to increase/reduce the frequency of the BUZZER\n" ) ;

         printf( "Press 'ESC' key to Exit this program\n\n" );

        

        

         while( 1 )

         {

                   int key;

 

                   set_buzzer_freq(freq);

                   printf( "\tFreq = %d\n", freq );

 

                   key = getch();

 

                   switch(key) {

                   case '+':

                            if( freq < 20000 )

                                     freq += 10;

                            break;

 

                   case '-':

                            if( freq > 11 )

                                     freq -= 10 ;

                            break;

 

                   case ESC_KEY:

                   case EOF:

                            stop_buzzer();

                            exit(0);

 

                   default:

                            break;

                   }

         }

}

通过调用ioctl函数实现控制PWM的频率以及关闭PWM.

1楼hshhduuduj4天前 22:05这里面好像没有实现占空比的改变，我现在想实现占空比改变，怎么搞？请教Re: ssdsafsdsd4天前 22:11回复hshhduudujn __raw_writel(tcnt/2, S3C2410_TCMPB(0));n这个是控制占空比的，根据你的需要仿照上面的设置频率的函数写个调整占空比的函数，不难。。。