PWM在ARM Linux中的原理和蜂鳴器驅(qū)動(dòng)實(shí)例開發(fā)

/*
================================================
Name : my2440_pwm.c
Author : Huang Gang
Date : 25/11/09
Copyright : GPL
Description : my2440 pwm driver
================================================
*/

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

#definePWM_MAJOR 0//主設(shè)備號(hào)
#definePWM_NAME"my2440_pwm"http://設(shè)備名稱

staticintdevice_major=PWM_MAJOR;//系統(tǒng)動(dòng)態(tài)生成的主設(shè)備號(hào)

//打開設(shè)備
staticintpwm_open(structinode*inode,structfile*file)
{
//對(duì)GPB0復(fù)用口進(jìn)行復(fù)用功能設(shè)置，設(shè)置為TOUT0 PWM輸出
s3c2410_gpio_cfgpin(S3C2410_GPB0,S3C2410_GPB0_TOUT0);

return0;
}

//關(guān)閉設(shè)備
staticintpwm_close(structinode*inode,structfile*file)
{
return0;
}

//對(duì)設(shè)備進(jìn)行控制
staticintpwm_ioctl(structinode*inode,structfile*file,unsignedintcmd,unsignedlongarg)
{
if(cmd<=0)//如果輸入的參數(shù)小于或等于0的話，就讓蜂鳴器停止工作
{
//這里又恢復(fù)GPB0口為IO口輸出功能，由原理圖可知直接給低電平可讓蜂鳴器停止工作
s3c2410_gpio_cfgpin(S3C2410_GPB0,S3C2410_GPB0_OUTP);
s3c2410_gpio_setpin(S3C2410_GPB0,0);
}
else//如果輸入的參數(shù)大于0，就讓蜂鳴器開始工作，不同的參數(shù)，蜂鳴器的頻率也不一樣
{
//定義一些局部變量
unsignedlongtcon;
unsignedlongtcnt;
unsignedlongtcfg1;
unsignedlongtcfg0;

structclk*clk_p;
unsignedlongpclk;

//以下對(duì)各寄存器的操作結(jié)合上面講的開始一個(gè)PWM定時(shí)器的步驟和2440手冊(cè)PWM寄存器操作部分來看就比較容易理解
tcfg1=__raw_readl(S3C2410_TCFG1);//讀取定時(shí)器配置寄存器1的值
tcfg0=__raw_readl(S3C2410_TCFG0);//讀取定時(shí)器配置寄存器0的值

tcfg0&=~S3C2410_TCFG_PRESCALER0_MASK;
tcfg0|=(50-1);//設(shè)置tcfg0的值為49

tcfg1&=~S3C2410_TCFG1_MUX0_MASK;
tcfg1|=S3C2410_TCFG1_MUX0_DIV16;//設(shè)置tcfg1的值為0x0011即：1/16

__raw_writel(tcfg1,S3C2410_TCFG1);//將值tcfg1寫入定時(shí)器配置寄存器1中
__raw_writel(tcfg0,S3C2410_TCFG0);//將值tcfg0寫入定時(shí)器配置寄存器0中

clk_p=clk_get(NULL,"pclk");
pclk=clk_get_rate(clk_p);//從系統(tǒng)平臺(tái)時(shí)鐘隊(duì)列中獲取pclk的時(shí)鐘頻率，在include/linux/clk.h中定義
tcnt=(pclk/50/16)/cmd;//計(jì)算定時(shí)器0的輸出時(shí)鐘頻率(pclk/{prescaler0 + 1}/divider value)

__raw_writel(tcnt,S3C2410_TCNTB(0));//設(shè)置定時(shí)器0計(jì)數(shù)緩存寄存器的值
__raw_writel(tcnt/2,S3C2410_TCMPB(0));//設(shè)置定時(shí)器0比較緩存寄存器的值

tcon=__raw_readl(S3C2410_TCON);//讀取定時(shí)器控制寄存器的值

tcon&=~0x1f;
tcon|=0xb;//關(guān)閉死區(qū)、自動(dòng)重載、關(guān)反相器、更新TCNTB0&TCMPB0、啟動(dòng)定時(shí)器0
__raw_writel(tcon,S3C2410_TCON);//設(shè)置定時(shí)器控制寄存器的0-4位，即對(duì)定時(shí)器0進(jìn)行控制

tcon&=~2;
__raw_writel(tcon,S3C2410_TCON);//清除定時(shí)器0的手動(dòng)更新位
}

return0;
}

//設(shè)備操作結(jié)構(gòu)體
staticstructfile_operations pwm_fops=
{
.owner=THIS_MODULE,
.open=pwm_open,
.release=pwm_close,
.ioctl=pwm_ioctl,
};

//定義一個(gè)設(shè)備類
staticstructclass*pwm_class;

staticint__init pwm_init(void)
{
//注冊(cè)為字符設(shè)備，主設(shè)備號(hào)為0讓系統(tǒng)自動(dòng)分配，設(shè)備名為my2440_pwm，注冊(cè)成功返回動(dòng)態(tài)生成的主設(shè)備號(hào)
device_major=register_chrdev(PWM_MAJOR,PWM_NAME,&pwm_fops);

if(device_major<0)
{
printk(PWM_NAME" register falid!/n");
returndevice_major;
}

//注冊(cè)一個(gè)設(shè)備類，使mdev可以在/dev/目錄下自動(dòng)建立設(shè)備節(jié)點(diǎn)
pwm_class=class_create(THIS_MODULE,PWM_NAME);

if(IS_ERR(pwm_class))
{
printk(PWM_NAME" register class falid!/n");
return-1;
}

//創(chuàng)建一個(gè)設(shè)備節(jié)點(diǎn)，設(shè)備名為PWM_NAME，即：my2440_pwm
device_create(pwm_class,NULL,MKDEV(device_major,0),NULL,PWM_NAME);

return0;
}

staticvoid__exit pwm_exit(void)
{
//注銷設(shè)備
unregister_chrdev(device_major,PWM_NAME);

//刪除設(shè)備節(jié)點(diǎn)
device_destroy(pwm_class,MKDEV(device_major,0));

//注銷設(shè)備類
class_destroy(pwm_class);
}

module_init(pwm_init);
module_exit(pwm_exit);

MODULE_LICENSE("PGL");
MODULE_AUTHOR("Huang Gang");
MODULE_DESCRIPTION("my2440 pwm driver");

#cp -f my2440_pwm.c /linux-2.6.30.4/drivers/char //把驅(qū)動(dòng)源碼到內(nèi)核驅(qū)動(dòng)的字符設(shè)備下

#gedit /linux-2.6.30.4/drivers/char/Kconfig //添加PWM蜂鳴器設(shè)備配置

config MY2440_PWM_BEEP
tristate"My2440 PWM Beep Device"
dependsonARCH_S3C2440
default y
---help---
My2440 PWM Beep

#gedit /linux-2.6.30.4/drivers/char/Makefile //添加PWM蜂鳴器設(shè)備配置

obj-$(CONFIG_MY2440_PWM_BEEP) +=my2440_pwm.o

#make menuconfig

Device Drivers --->
Character devices --->
<*> My2440 PWM Beep Device (NEW)

/*
==============================================
Name : pwm_test.c
Author : Huang Gang
Date : 25/11/2009
Copyright : GPL
Description : my2440 pwm driver test
==============================================
*/

#include
#include
#include
#include

intmain(intargc,char**argv)
{
inttmp;
intfd;
inti;

//打開蜂鳴器設(shè)備
fd=open("/dev/my2440_pwm",O_RDWR);

if(fd<0)
{
printf("Open PWM Device Faild!/n");
exit(1);
}

//提示用戶輸入一個(gè)參數(shù)來對(duì)蜂鳴器進(jìn)行調(diào)頻，0表示停止工作
printf("please enter the times number(0 is stop):/n");

while(1)
{
//輸入?yún)?shù)
scanf("%d",&tmp);
printf("times = %d/n",tmp);

//IO控制
ioctl(fd,tmp);

if(tmp<=0)
{
break;
}
}

//關(guān)閉設(shè)備
close(fd);

return0;
}

#arm-linux-gcc -o pwm_test pwm_test.c