用火机烧DS18B20，就升高了0.几度，估计算法有问题，也不排除驱动问题！![]()
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/uaccess.h>
#include <linux/clk.h>
#include <mach/regs-gpio.h>
#include <mach/io.h>
#include <mach/map.h>
#include <mach/regs-clock.h>
#define DQ S3C2410_GPG11
#define CPGIN S3C2410_GPG11_INP
#define CPGOUT S3C2410_GPG11_OUTP
#define DEVICE_NAME "xiaolei.wang-18b20"
#define DS18B20_MOJOR 210
static int opencount=0;
static char data[2];
//ds18b20复位00成功1失败
static unsigned char init_ds18b20(void)
{
unsigned char ret=0;
// s3c2410_gpio_cfgpin(S3C2410_GPG11,S3C2410_GPG11_OUTP);
s3c2410_gpio_cfgpin(DQ,CPGOUT);
//s3c2410_gpio_pulllup(DQ,0);
s3c2410_gpio_setpin(DQ,1);
udelay(100);//并保持高电平状态约100微秒
s3c2410_gpio_setpin(DQ,0);
udelay(500);
s3c2410_gpio_setpin(DQ,1);
udelay(50);
s3c2410_gpio_cfgpin(DQ,CPGIN);
// 通过再次配置GPG11引脚成输入状态，可以检测到DS18B20是否复位成功
//若存在脉冲是一个60~240us的低电平信号，则通信双方已达成基本的协议
ret=s3c2410_gpio_getpin(DQ);
udelay(200);
return ret;
}
static void write_char(char data)
{
unsigned char i=0;
s3c2410_gpio_cfgpin(DQ,CPGOUT);
s3c2410_gpio_pullup(DQ,1);
for(i=0;i<8;i++)
{
s3c2410_gpio_setpin(DQ, 0); //每一位的发送前至少15us低电平起始位
udelay(15);
s3c2410_gpio_setpin(DQ, data&0x01); //在采样时间内，如果控制器将总线拉高，表示写1，拉低表示写0
udelay(60);
s3c2410_gpio_setpin(DQ,1);
udelay(2);
data>>=1;
}
}
static unsigned char read_char(void)
{
unsigned char i;
unsigned char data;
for(i=0;i<8;i++)
{
s3c2410_gpio_setpin(DQ,CPGOUT);
s3c2410_gpio_setpin(DQ, 0);//读时间间隙时也是必须先有主机产生至少1us的低电平，表示读时间的起始
udelay(1);
data>>=1;
s3c2410_gpio_setpin(DQ,1);
s3c2410_gpio_setpin(DQ,CPGIN);
if(s3c2410_gpio_getpin(DQ))
data|=0x80;
udelay(50);
}
return data;
}
static ssize_t read_ds18b20(struct file *filp, char *buffer, size_t count, loff_t *ppos)
{
if(init_ds18b20())
return -1;
write_char(0x0cc);//跳过度序列号操作
write_char(0x0be);//读取温度寄存器
data[0]=read_char();//读低八位
data[1]=read_char();//度高八位
buffer[0]=data[0];
buffer[1]=data[1];
return 1;
}
static int open_ds18b20(struct inode *node, struct file *file)
{
unsigned char flag;
if(opencount==1)
return -EBUSY;
flag=init_ds18b20();
if(flag&0x01)
{
printk("uable to open device!!\n");
return -1;
}
else
{
opencount++;
printk("sucess to open device!!\n");
return 0;
}
}
static int release_ds18b20(struct inode *node, struct file *file)
{
opencount--;
printk("device is close\n");
return 0;
}
static struct file_operations ds18b20_fops={
.owner=THIS_MODULE,
.read=read_ds18b20,
.open=open_ds18b20,
.release=release_ds18b20,
};
static char __initdata banner[]="TQ2440/xux ds18b20\n";
static struct class *ds18b20_class;
static int __init ds18b20_init(void)
{
int ret;
printk(banner);
ret= register_chrdev(DS18B20_MOJOR,DEVICE_NAME,&ds18b20_fops);
if (ret < 0)
{
printk(DEVICE_NAME " can't register major number\n");
return ret;
}//错误处理
ds18b20_class=class_create(THIS_MODULE,DEVICE_NAME);
if(IS_ERR(ds18b20_class))
{
printk("Err: failed in tope-leds class. \n");
return -1;
}
device_create(ds18b20_class, NULL, MKDEV(DS18B20_MOJOR, 0), NULL, DEVICE_NAME);//创建一个设备节点，节点名为DEVICE_NAME
printk(DEVICE_NAME " initialized\n");//打印信息，内核中的打印用printk函数
return 0;
}
static void __exit ds18b20_exit(void)
{
printk(DEVICE_NAME " exit\n");//打印信息，内核中的打印用printk函数
unregister_chrdev(DS18B20_MOJOR, DEVICE_NAME);//取消注册设备
device_destroy(ds18b20_class, MKDEV(DS18B20_MOJOR, 0)); //删掉设备节点
class_destroy(ds18b20_class); //注销类
}
module_init(ds18b20_init);
module_exit(ds18b20_exit);
MODULE_LICENSE("GPL");//遵循的协议 |
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