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关键词:Android linux hrtimer 蜂鸣器 等待队列 信号量 字符设备
平台信息:
内核:linux3.4.39
系统:android/android5.1
平台:S5P4418
作者:庄泽彬(欢迎转载,请注明作者)
邮箱:2760715357@qq.com
程序描述:本文控制的设备是无源蜂鸣器,由于无源蜂鸣器是需要产生一定的频率的PWM才能够控制蜂鸣器,不像有源蜂鸣器,只需要提供高低电平就可以控制蜂鸣器。linux内核普通的定时器,由于具有一定的局限性,不能达到纳秒级别的定时,使用普通的定时器模拟GPIO口产生PWM会导致蜂鸣器出现杂音,因此要使用hrtimer高精度定时器模拟GPIO口产生PWM可以极大的改善性能。使用信号量sem只是为了避免多个应用程序打开设备,使用等待队列是为了让程序可以按照指定的方式去运行,如果不加等待队列,在启动hrtimer定时器之后就会不会等待定时器完成之后在关闭设备,因此需要加入等待队列,等待定时器定时的工作完成之后再唤醒等待队列。虽然程序可以使用GPIO模拟PWM产生一定频率的信号去控制无源蜂鸣器,但是还是存在一定的局限性,因为定时器也是加入内核进行调度,所以有可能杂定时的时候会导致输出的PWM被打断,导致杂音的出现。因此严格来说不能完整的输出一段不被打断模拟PWM信号。如果有什么好方法可以实现的话,可以共同探讨。好吧不说了上代码吧。
无源蜂鸣器的驱动程序(代码写的一般般如有不对,欢迎指点)
buzzer_driver.c
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/cdev.h>
#include <linux/interrupt.h>
#include <linux/gpio.h>
#include <linux/input.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/delay.h>
#include <linux/semaphore.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <mach/platform.h>
#define BUZZER_DEVICE_NAME "mybuzzer"
#define BUZZER_CLASS_NAME "mybuzzer" //sys/class/mybuzzer
#define BUZZER_DEVICE_NUM 1 //设备节点的编号最终生成节点的名字为/dev/buzzer-1
#define BUZZER_GPIO_SWITCH 1 //是否设置buzzer的gpio的初始化,另一个驱动已经初始化GPIO
#define BUZZER_DELAY_TIME_HIGHT (190000) //2.7KHZ
#define BUZZER_DELAY_TIME_LOW (190000) //2.7KHZ
#define DE_BUG 1
#if DE_BUG
#define prdebug(fmt,arg...) printk("zbzhuang"KERN_ERR fmt"\n",##arg)
#else
#define prdebug(fmt,arg...) do{}while(0);
#endif
typedef enum {
BUZZER_DISABLE = 0,
BUZZER_ENABLE,
}BUZZER_STATUS_t;
//buzzer的设备对象
struct buzzer_chip{
dev_t devno;
struct cdev *cdev;
struct class *cls;
struct device *dev;
unsigned long count; //从应用空间读取的数据
struct semaphore sem;
struct hrtimer mytimer;
ktime_t kt; //设置定时时间
wait_queue_head_t wait_queue;
BUZZER_STATUS_t status;
};
static int count = 1000;
struct buzzer_chip *buzzer_dev;
static void buzzer_test(void);
static void buzzer_gpio_start(void);
static enum hrtimer_restart hrtimer_handler(struct hrtimer *timer);
int buzzer_drv_open (struct inode * inode, struct file *filp)
{
int minor;
int major;
prdebug("--------------%s----------------",__func__);
minor = iminor(inode);
major = imajor(inode);
prdebug("\r\nmajor = %d minor = %d\rn",major,minor);
filp->private_data = (void *)minor;
if(down_interruptible(&buzzer_dev->sem))
return -ERESTARTSYS;
return 0;
}
ssize_t buzzer_drv_read (struct file *filp, char __user *userbuf, size_t count, loff_t *fpos)
{
int ret;
prdebug("--------------%s----------------",__func__);
if(filp->f_flags & O_NONBLOCK){
return -EAGAIN;
}
ret = copy_to_user(userbuf,&buzzer_dev->count,count);
if(ret > 0){
prdebug("error copy_to_user");
return -EFAULT;
}
prdebug("%s :read count = %ld",__func__,buzzer_dev->count);
return count;
}
ssize_t buzzer_drv_write (struct file *filp, const char __user *userbuf, size_t count, loff_t *fpos)
{
int ret;
prdebug("--------------%s----------------",__func__);
prdebug("task pid[%d] context[%s]",current->pid,current->comm);
ret = copy_from_user(&buzzer_dev->count,userbuf,count);
if(ret > 0){
prdebug("error copy_from_user");
return -EFAULT;
}
prdebug("%s :write count = %ld",__func__,buzzer_dev->count);
if(buzzer_dev->count){
if(buzzer_dev->status == BUZZER_DISABLE){
//启动定时器
prdebug("-----------start hrtimer timer-------------");
buzzer_dev->status = BUZZER_ENABLE;
buzzer_gpio_start();
wait_event(buzzer_dev->wait_queue, buzzer_dev->status == BUZZER_DISABLE);
prdebug("------------wake up queue-------------------------------");
}else{
prdebug("buzzer_aready work");
}
}else{
}
return count;
}
int buzzer_drv_close (struct inode *inode, struct file *filp)
{
prdebug("--------------%s----------------",__func__);
up(&buzzer_dev->sem);
return 0;
}
const struct file_operations buzzer_fops = {
.open = buzzer_drv_open,
.write = buzzer_drv_write,
.read = buzzer_drv_read,
.release = buzzer_drv_close,
};
static int buzzer_gpio_init(void)
{
int ret = -1;
if(gpio_request(BUZZER_IO, "BUZZER_GPIO")){
prdebug("error buzzer_gpio_init");
return ret;
}else{
gpio_direction_output(BUZZER_IO, 1);
gpio_set_value(BUZZER_IO, 1);
buzzer_dev->status = BUZZER_DISABLE;
}
return 0;
}
static void buzzer_gpio_exit(void)
{
gpio_set_value(BUZZER_IO, 1);
gpio_free(BUZZER_IO);
}
static void buzzer_gpio_start(void)
{
prdebug("-----------buzzer_gpio_start------------");
//高精度定时器
hrtimer_init(&buzzer_dev->mytimer,CLOCK_MONOTONIC,HRTIMER_MODE_REL);
buzzer_dev->mytimer.function = hrtimer_handler;
buzzer_dev->kt = ktime_set(0, BUZZER_DELAY_TIME_LOW);
hrtimer_start(&buzzer_dev->mytimer,buzzer_dev->kt,HRTIMER_MODE_REL);
}
static void buzzer_test(void)
{
unsigned long i;
prdebug("-----------start test buzzer------------");
for(i = 0;i < 10000;i ++){
gpio_set_value(BUZZER_IO, 0);
udelay(150);
gpio_set_value(BUZZER_IO, 1);
udelay(150);
}
prdebug("-----------end test buzzer------------");
}
static enum hrtimer_restart hrtimer_handler(struct hrtimer *timer)
{
//prdebug("--------------%s----------------",__func__);
if(buzzer_dev->count != 1){
if (gpio_get_value(BUZZER_IO) == 1) {
gpio_set_value(BUZZER_IO, 0);
buzzer_dev->kt = ktime_set(0, BUZZER_DELAY_TIME_LOW);
hrtimer_forward_now(&buzzer_dev->mytimer, buzzer_dev->kt);
} else {
gpio_set_value(BUZZER_IO, 1);
buzzer_dev->kt = ktime_set(0, BUZZER_DELAY_TIME_HIGHT);
hrtimer_forward_now(&buzzer_dev->mytimer, buzzer_dev->kt);
}
buzzer_dev->count --;
return HRTIMER_RESTART;
}else{
buzzer_dev->count --;
buzzer_dev->status = BUZZER_DISABLE;
prdebug("buzzer_dev->count = %d",buzzer_dev->count);
prdebug("-----------finsh hrtimer timer-------------");
wake_up(&buzzer_dev->wait_queue);
return HRTIMER_NORESTART;
}
}
static int __init buzzer_drv_init(void)
{
int ret;
prdebug("--------------%s----------------",__func__);
buzzer_dev = kzalloc(sizeof(struct buzzer_chip),GFP_KERNEL);
if(buzzer_dev == NULL){
prdebug("kzalloc error");
return -ENOMEM;
}
//动态的申请设备号
ret = alloc_chrdev_region(&buzzer_dev->devno,0,1,BUZZER_DEVICE_NAME);
if(ret != 0){
prdebug("error alloc_chrdev_region");
goto err_free;
}
//分配cdev对象
buzzer_dev->cdev = cdev_alloc();
cdev_init(buzzer_dev->cdev,&buzzer_fops);
cdev_add(buzzer_dev->cdev,buzzer_dev->devno,1);
//自动创建设备节点
buzzer_dev->cls = class_create(THIS_MODULE,BUZZER_CLASS_NAME);
if(IS_ERR(buzzer_dev->cls)){
prdebug("error class_create");
ret = PTR_ERR(buzzer_dev->cls);
goto err_unregister;
}
buzzer_dev->dev = device_create(buzzer_dev->cls,NULL,buzzer_dev->devno,NULL,"buzzer-%d",BUZZER_DEVICE_NUM);
if(IS_ERR(buzzer_dev->dev)){
prdebug("error device_create");
ret = PTR_ERR(buzzer_dev);
goto err_class_error;
}
//信号量
sema_init(&buzzer_dev->sem,1);
init_waitqueue_head(&buzzer_dev->wait_queue);
#if BUZZER_GPIO_SWITCH
//初始化Buzzer的GPIO
ret = buzzer_gpio_init();
if(ret !=0){
prdebug("error buzzer_gpio_init");
goto err_device_create;
}
#endif
return 0;
#if BUZZER_GPIO_SWITCH
err_device_create:
device_destroy(buzzer_dev->cls,buzzer_dev->devno);
#endif
err_class_error:
class_destroy(buzzer_dev->cls);
err_unregister:
cdev_del(buzzer_dev->cdev);
unregister_chrdev_region(buzzer_dev->devno,1);
err_free:
kfree(buzzer_dev);
return ret;
}
static void __exit buzzer_drv_exit(void)
{
prdebug("--------------%s----------------",__func__);
#if BUZZER_GPIO_SWITCH
buzzer_gpio_exit();
#endif
device_destroy(buzzer_dev->cls,buzzer_dev->devno);
class_destroy(buzzer_dev->cls);
cdev_del(buzzer_dev->cdev);
unregister_chrdev_region(buzzer_dev->devno,1);
kfree(buzzer_dev);
}
module_init(buzzer_drv_init);
module_exit(buzzer_drv_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("zhuang zebin@qq.com");
欢迎大家来到IT世界,在知识的湖畔探索吧!
驱动程序对应的Makefile,自己修改交叉工具链还有内核的位置
欢迎大家来到IT世界,在知识的湖畔探索吧!CROSS_COMPILE = /home/zsf/u4209/s5p4418-5.1-android/trunk/prebuilts/gcc/linux-x86/arm/arm-eabi-4.8/bin/arm-eabi-
#CROSS_COMPILE = /home/zsf/book/toolchain-4.5.1-farsight/bin/arm-none-linux-gnueabi-
CC = $(CROSS_COMPILE)gcc
#APP_NAME = led_app
MODULE_NAME = buzzer_driver
#内核源码路径
#KERNEL_DIR = /home/zsf/rk3188_5.1/android/kernel
KERNEL_DIR = /home/zsf/u4209/s5p4418-5.1-android/trunk/kernel
CUR_DIR = $(shell pwd)
all :
make -C $(KERNEL_DIR) M=$(CUR_DIR) modules
#$(CC) $(APP_NAME).c -o $(APP_NAME)
clean :
make -C $(KERNEL_DIR) M=$(CUR_DIR) clean
#rm -rf $(APP_NAME)
install:
cp -raf *.ko $(APP_NAME) /opt/rootfs/drv_module/
#指定编译哪个源文件
obj-m = $(MODULE_NAME).o
~
写一个简单的APP去控制设备代码如下buzzer_write.c:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
int main(int argc,char **argv)
{
int fd = -1;
unsigned long on = -1;
fd = open("/dev/buzzer-1",O_RDWR);
if(fd < 0){
perror("open");
exit(1);
}
on = atol(argv[1]);
write(fd,&on,4);
close(fd);
return 0;
}
对应的Android.mk
欢迎大家来到IT世界,在知识的湖畔探索吧!LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE := buzzer_write
LOCAL_SRC_FILES := buzzer_write.cpp
include $(BUILD_EXECUTABLE)
编译驱动:错误和警告可以忽略,之后使用adb工具将buzzer_driver.ko推送进板子。
编译应用程序
实验操作如下:
查看相应的LOG
这里无法展示你们看,蜂鸣器的叫声,经过测试改程序勉强还是可以使用的啊。
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