基于FL2440开发板实现蜂鸣器唱歌的原理

1. 蜂鸣器唱歌的原理: 由于定时器可以发出不同频率，不同占空比的pwm波。当蜂鸣器接收这些波形时，由于频率和占空比的不同，它会发出频率及声音大小不同的响声，即不同的音色和响度。这样就可以唱歌了。所以我们要做的就是在底层驱动程序中设置相关的定时器的寄存器，注册字符设备。在应用程序中通过ioctl改变定时器的占空比。

2. 驱动程序

#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>

static struct class *pwm_class;
static struct device *pwm_class_dev;
#define DEVICE_NAME "pwm" ?#define PWM_IOCTL_SET_FREQ 1 //定义宏变量,用于后面的 ioctl 中的控制命令
#define PWM_IOCTL_STOP 0 //定义信号量 lock

//定义信号量 lock用于互斥，因此，该驱动程序只能同时有一个进程使用
static struct semaphore lock;

/* freq: pclk/50/16/65536 ~ pclk/50/16
* if pclk = 50MHz, freq is 1Hz to 62500Hz
* human ear(人儿能辨别的) : 20Hz~ 20000Hz
*/
/*配置各个寄存器，设置PWM的频率*/
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;

//设置GPB0 为TOUT0,pwm 输出
s3c2410_gpio_cfgpin(S3C2410_GPB0, S3C2410_GPB0_TOUT0);

/*读取定时器控制寄存器的数值*/
tcon = __raw_readl(S3C2410_TCON);
/*读取定时器配置寄存器1的值*/
tcfg1 = __raw_readl(S3C2410_TCFG1);
/*读取定时器配置寄存器0的值*/
tcfg0 = __raw_readl(S3C2410_TCFG0);

/*设置预分频prescaler = 50*/
//S3C2410_TCFG_PRESCALER0_MASK定时器0 和1 的预分频值的掩码，TCFG[0~7]
tcfg0 &= ~S3C2410_TCFG_PRESCALER0_MASK;//低八位清零
tcfg0 |= (50 - 1); //设置预分频为50

/*设置分频值为16*/
//S3C2410_TCFG1_MUX0_MASK 定时器0 分割值的掩码TCFG1[0~3]
tcfg1 &= ~S3C2410_TCFG1_MUX0_MASK;
//定时器0 进行16 分割
tcfg1 |= S3C2410_TCFG1_MUX0_DIV16;

/*将设置的参数值写入相应的寄存器中*/
//把tcfg1 的值写到分割寄存器S3C2410_TCFG1 中
__raw_writel(tcfg1, S3C2410_TCFG1);
//把tcfg0 的值写到预分频寄存器S3C2410_TCFG0 中
__raw_writel(tcfg0, S3C2410_TCFG0);

/*开启对应时钟源，并获取pclk*/
clk_p = clk_get(NULL, "pclk");
//获得pclk的时钟频率
pclk = clk_get_rate(clk_p);

/*得到定时器的输入时钟，进而设置PWM的调制频率和占空比*/
tcnt = (pclk/50/16)/freq;
//PWM 脉宽调制的频率等于定时器的输入时钟
__raw_writel(freq, S3C2410_TCNTB(0));
//占空比是50%
__raw_writel(freq/2, S3C2410_TCMPB(0));

/*失能死区，开启自动重载, 关闭变相, 更新TCNTB0&TCMPB0, 启动timer0*/
tcon &= ~0x1f;
tcon |= 0xb;
//把tcon 写到计数器控制寄存器S3C2410_TCON 中
__raw_writel(tcon, S3C2410_TCON);

//clear manual update bit
tcon &= ~2;
__raw_writel(tcon, S3C2410_TCON);
}

static void pwm_stop(void)
{
//设置GPB0 为输出
s3c2410_gpio_cfgpin(S3C2410_GPB0, S3C2410_GPIO_OUTPUT);
//设置GPB0 为低电平，使蜂鸣器停止
s3c2410_gpio_setpin(S3C2410_GPB0, 0);
}

static int pwm_open(struct inode *inode, struct file *file)
{
if (!down_trylock(&lock)) //是否获得信号量，是down_trylock(&lock）=0，否则非0
return 0;
else
return -EBUSY; //返回错误信息：请求的资源不可用
}
static int pwm_close(struct inode *inode, struct file *file)
{
pwm_stop();
//释放信号量lock
up(&lock);
return 0;
}

/*cmd 是1，表示设置频率；cmd 是2 ，表示停止pwm*/
static int pwm_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
switch (cmd)
{
case PWM_IOCTL_SET_FREQ: //if cmd=1 即进入case PWM_IOCTL_SET_FREQ
if (arg == 0) //如果设置的频率参数是0
return -EINVAL; //返回错误信息，表示向参数传递了无效的参数
PWM_Set_Freq(arg); //否则设置频率
break;
case PWM_IOCTL_STOP: // if cmd=0 即进入case PWM_IOCTL_STOP
pwm_stop(); //停止蜂鸣器
break;
}
return 0; //成功返回
}

/*初始化设备的文件操作的结构体*/
static struct file_operations pwm_fops = {
.owner = THIS_MODULE,
.open = pwm_open,
.release = pwm_close,
.ioctl = pwm_ioctl,
};

int major;
static int __init pwm_init(void)
{

init_MUTEX(&lock);

major = register_chrdev(0, DEVICE_NAME, &pwm_fops);

if(major < 0)
{
printk(DEVICE_NAME "register falid!\n");
return major;
}
printk (DEVICE_NAME " initialized!\n");
pwm_class = class_create(THIS_MODULE, DEVICE_NAME);

pwm_class_dev = device_create(pwm_class, NULL, MKDEV(major, 0), NULL, "mas"); /* /dev/mas */

return 0;
}
static void __exit pwm_exit(void)
{
device_unregister(pwm_class_dev);
class_destroy(pwm_class);
unregister_chrdev(major, DEVICE_NAME);
}
module_init(pwm_init);
module_exit(pwm_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("DreamCatcher");
MODULE_DESCRIPTION("MINI2440 PWM Driver");


3. 应用程序
#include <stdio.h>
#include <termios.h> //POSIX终端控制定义
#include <unistd.h> //Unix 标准函数定义
#include <stdlib.h>

#define PWM_IOCTL_SET_FREQ 1
#define PWM_IOCTL_STOP 0

unsigned int muiscscore[]={239,213,189,179,159,142,127,120,
120,106,95,90,80,71,64,60,
60,53,47,45,40,36,32,30};
unsigned int sszymmh[]={13,3, 12,1, 10,2, 12,2, 16,2, 13,1, 12,1, 13,4,
10,2, 12,1, 13,1, 12,2, 10,1, 9,1, 8,1, 5,1,
12,1, 10,1, 9,4, 9,3, 10,1, 12,2, 12,1, 13,1, 10,3,
9,1, 8,4, 12,3, 10,1, 9,1, 8,1, 5,1, 9,1, 5,4, 0,0,};

static int fd = -1;

static void close_buzzer(void);
static void open_buzzer(void) //打开蜂鸣器
{
fd = open("/dev/mas", 0); //打开pwm设备驱动文件
if (fd < 0) {
perror("open pwm_buzzer device"); //打开错误，则终止进程。退出参数为1
exit(1);
}

// any function exit call will stop thebuzzer
atexit(close_buzzer); //退出回调close_buzzer
}

static void close_buzzer(void) //关闭蜂鸣器
{
if (fd >= 0) {
ioctl(fd, PWM_IOCTL_STOP); //停止蜂鸣器
close(fd); //关闭设备驱动文件
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); //设置频率

}
static void stop_buzzer(void) //关闭蜂鸣器
{
int ret = ioctl(fd, PWM_IOCTL_STOP);
if(ret < 0) {
perror("stop the buzzer");
exit(1);
}
}
void delay(unsigned int t)
{
unsigned int t1;
unsigned long t2;
for(t1=0;t1<t*137;t1++)
{

for(t2=0;t2<58000;t2++)
{
;
}
}
}
int main(int argc, char **argv)
{
int freq;
unsigned int k;
int i=0;
unsigned int time;

open_buzzer(); //打开蜂鸣器

printf( "\nBUZZER TEST ( PWMControl )\n" );
printf( "Press +/- to increase/reduce the frequency of theBUZZER\n" ) ;
printf( "Press 'ESC' key to Exit this program\n\n" );

while(1)
{

k=sszymmh[i];
freq=muiscscore[k];
time=sszymmh[i+1];
set_buzzer_freq(freq); //设置蜂鸣器频率
//sleep(freq/2);

delay(time);
i=i+2;
if(i==70)
{
close_buzzer();
exit(0);
i=0;
}

}
}