#include <linux/module.h>#include <linux/kernel.h>#include <linux/miscdevice.h> /*杂项字符设备头文件*/#include <linux/fs.h> /*文件操作集合*/#include <linux/delay.h> /*延时函数*/
#include <linux/uaccess.h>#include <asm/io.h>
/*DS18B20 GPIO接口: GPB_4*/
/*定义指针，用于接收虚拟地址*/volatile unsigned int *DS18B20_GPBCON;volatile unsigned int *DS18B20_GPBDAT;
#define DS18B20_INPUT() {*DS18B20_GPBCON &= ~(0xf << 4 * 4);}#define DS18B20_OUTPUT() {*DS18B20_GPBCON &= ~(0xf << 4 * 4);*DS18B20_GPBCON |= (0x1 << 4 * 4);}
/*函数功能：等待DS18B20的回应返回1:未检测到DS18B20的存在返回0:存在*/unsigned char DS18B20_Check(void) { unsigned char retry=0; DS18B20_INPUT() ///SET PG11 INPUT while((*DS18B20_GPBDAT & (1 << 4))&&retry<200) { retry++; udelay(1); }; if(retry>=200)return 1; else retry=0; while(!(*DS18B20_GPBDAT & (1 << 4))&&retry<240) { retry++; udelay(1); }; if(retry>=240)return 1; return 0;}
/*从DS18B20读取一个位返回值：1/0*/unsigned char DS18B20_Read_Bit(void) // read one bit{ unsigned char data; DS18B20_OUTPUT(); *DS18B20_GPBDAT &= ~(1 << 4);//输出0 udelay(2); *DS18B20_GPBDAT |= (1 << 4);//输出1 DS18B20_INPUT() udelay(12); if((*DS18B20_GPBDAT & (1 << 4)))data=1; else data=0; udelay(50); return data;}
/*从DS18B20读取一个字节返回值：读到的数据*/unsigned char DS18B20_Read_Byte(void) // read one byte{ unsigned char i,j,dat; dat=0; for(i=1;i<=8;i++) { j=DS18B20_Read_Bit(); dat=dat>>1; if(j) //主机对总线采样的数 判断-------读数据-1就是1，否则就是0 dat|=0x80; //先收低位数据--一步一步向低位移动>> } return dat;}
/*写一个字节到DS18B20dat：要写入的字节*/void DS18B20_Write_Byte(unsigned char dat) { unsigned char j; unsigned char testb; DS18B20_OUTPUT(); for(j=1;j<=8;j++) { testb=dat&0x01; dat=dat>>1; if(testb) { *DS18B20_GPBDAT &= ~(1 << 4);//输出0// Write 1 udelay(2); *DS18B20_GPBDAT |= (1 << 4);//输出1 udelay(60); } else { *DS18B20_GPBDAT &= ~(1 << 4);//输出0// Write 0 udelay(60); *DS18B20_GPBDAT |= (1 << 4);//输出1 udelay(2); } }}
/*从ds18b20得到温度值精度：0.1C返回值：温度值 （-550~1250） */short DS18B20_Get_Temp(void){ unsigned short aaa; unsigned char temp; unsigned char TL,TH; DS18B20_OUTPUT(); *DS18B20_GPBDAT &= ~(1 << 4);//输出0 //拉低DQ udelay(750); //拉低750us *DS18B20_GPBDAT |= (1 << 4);//输出1 //DQ=1 udelay(15); //15US DS18B20_Check(); DS18B20_Write_Byte(0xcc); DS18B20_Write_Byte(0x44); DS18B20_OUTPUT(); *DS18B20_GPBDAT &= ~(1 << 4);//输出0 //拉低DQ udelay(750); //拉低750us *DS18B20_GPBDAT |= (1 << 4);//输出1 //DQ=1 udelay(15); //15US DS18B20_Check(); DS18B20_Write_Byte(0xcc);// skip rom DS18B20_Write_Byte(0xbe);// convert TL=DS18B20_Read_Byte(); // LSB TH=DS18B20_Read_Byte(); // MSB aaa=((unsigned short)TH<<8)|TL; return aaa;}
/*杂项字符设备注册示例----->DS18B20*/static int tiny4412_open(struct inode *my_inode, struct file *my_file){ /*映射物理地址*/ DS18B20_GPBCON=ioremap(0x11400040,4); DS18B20_GPBDAT=ioremap(0x11400044,4); printk("DS18B20初始化成功!\r\n"); /*设置ds18b20为输出模式*/ *DS18B20_GPBCON &= ~(0xf << 4 * 4); *DS18B20_GPBCON |= (0x1 << 4 * 4); return 0;}
static int tiny4412_release(struct inode *my_inode, struct file *my_file){ /*释放虚拟地址*/ iounmap(DS18B20_GPBCON); iounmap(DS18B20_GPBDAT); printk("DS18B20释放成功\r\n"); return 0;}
static ssize_t tiny4412_read(struct file *my_file, char __user *buf, size_t len, loff_t *loff){ /*读取温度信息*/ short temp=DS18B20_Get_Temp(); copy_to_user(buf,&temp,2); //拷贝温度至应用层 return 0;}
static ssize_t tiny4412_write(struct file *my_file, const char __user *buf, size_t len, loff_t *loff){ return 0;}
/*文件操作集合*/static struct file_operations tiny4412_fops={ .open=tiny4412_open, .read=tiny4412_read, .write=tiny4412_write, .release=tiny4412_release};
/*核心结构体*/static struct miscdevice tiny4412_misc={ .minor=MISC_DYNAMIC_MINOR, /*自动分配次设备号*/ .name="DS18B20", /*设备文件，指定/dev/生成的文件名称*/ .fops=&tiny4412_fops};
static int __init DS18B20_dev_init(void){ /*杂项设备注册*/ misc_register(&tiny4412_misc); return 0;}
static void __exit DS18B20_dev_exit(void){ /*杂项设备注销*/ misc_deregister(&tiny4412_misc);}module_init(DS18B20_dev_init); module_exit(DS18B20_dev_exit);MODULE_LICENSE("GPL");
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