首页 / 操作系统 / Linux / DS18B20 Linux驱动程序 基于AT91SAM9260

调试了很久的DS18B20驱动，前些日子出现的问题一直是读出为0 ，卡了4天之后终于解决了，之前在控制口没有加上拉电阻，后来想到可能是这个问题，加了个大电阻，果然好了~#include <linux/kernel.h>#include <linux/module.h>#include <linux/sched.h>#include <linux/delay.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/miscdevice.h>#include <asm/uaccess.h>#include <mach/board.h>#include <mach/gpio.h>#include <linux/device.h>#define DEV_NAME "ds18b20"#define PFX "ds18b20: "#define ds18b20_MINOR 120 /*minor number of this ds18b20*//*commad*/#define SKIP_ROM  0xCC /*skip rom operation*/#define TEMP_CONVET 0x44 /*start temperature convertion*/#define READ_TEMP  0xBE /*start read temperature*/#define HIGH 1#define LOW  0static int char_major=231;unsigned char data[2];/** ds18s20_set_input:** @action: set input and pull low** @index: sensor select** @return: none*/static void ds18s20_set_input（int high）{if（high）{at91_set_gpio_input（AT91_PIN_PA24, HIGH）;}else{at91_set_gpio_input（AT91_PIN_PA24, LOW）;}}/** ds18b20_set_output:** @action: set output and clear io** @index: sensor select** @return: none*/static void ds18b20_set_output（ int high）{if（high）{ at91_set_gpio_output（AT91_PIN_PA24, HIGH）;}
if（！high）{at91_set_gpio_output（AT91_PIN_PA24, LOW）;}}/** ds18b20_get_io:** @action: get io value** @index: sensor select** @return: 1 for success*      0 for failure */static unsigned char ds18b20_get_io（void）{unsigned char ret = 0; ret = at91_get_gpio_value（AT91_PIN_PA24）;return ret;}/** ds18b20_write_byte:** @action: write byte to ds18b20 register** @b: the data value ready to write** @index: sensor select** @return: none*/static unsigned char ds18b20_write_byte（unsigned char b）//b=skip ROM operation{int i;/*    // 写“1”时隙：    //     保持总线在低电平1微秒到15微秒之间    //     然后再保持总线在高电平15微秒到60微秒之间    //     理想状态: 1微秒的低电平然后跳变再保持60微秒的高电平    //    // 写“0”时隙：    //     保持总线在低电平15微秒到60微秒之间    //     然后再保持总线在高电平1微秒到15微秒之间    //     理想状态: 60微秒的低电平然后跳变再保持1微秒的高电平   */ for（i=0;i<8;i++）{ if（b&1）{ds18b20_set_output（LOW）;udelay（8）;ds18b20_set_output（HIGH）;udelay（55）;}else{ds18b20_set_output（LOW）;udelay（55）;ds18b20_set_output（HIGH）;udelay（8）;}
b>>=1;}
return b; }/** ds18b20_read_byte:** @action: read data value（byte） form register** @index: sensor select** @return: data value*/static unsigned char ds18b20_read_byte（void）{unsigned char i=0,byte=0;for（i=0;i<8;i++）{byte>>=1;ds18b20_set_output（LOW）;udelay（1）;
ds18b20_set_output（HIGH）;udelay（1）;
ds18s20_set_input（HIGH）; if（ds18b20_get_io（））byte|=0x80;udelay（60）;}
return byte;    // 读“1”时隙：    //     若总线状态保持在低电平状态1微秒到15微秒之间    //     然后跳变到高电平状态且保持在15微秒到60微秒之间    //      就认为从DS18B20读到一个“1”信号    //     理想情况: 1微秒的低电平然后跳变再保持60微秒的高电平    //    // 读“0”时隙：    //     若总线状态保持在低电平状态15微秒到30微秒之间    //     然后跳变到高电平状态且保持在15微秒到60微秒之间    //     就认为从DS18B20读到一个“0”信号    //     理想情况: 15微秒的低电平然后跳变再保持46微秒的高电平}/** ds18b20_reset:** @action: reset ds18b20** @index: sensor select** @return: 1 for success*      0 for failure */static int ds18b20_reset（void）{ ds18b20_set_output（HIGH）;ds18b20_set_output（LOW）;//udelay（500）;ds18b20_set_output（HIGH）; ds18s20_set_input（HIGH）;//set input modeudelay（15）;//wait 15-60us DS18b20 will respondds18b20_get_io（）;//if answer is 0printk（"DS18b20 respond 0 "）;//ds18b20_set_output（HIGH）;udelay（800）;
return 0;}/** ds18b20_reset:** @action: read temperature** @index: sensor select** @return: current temperature */static int ds18b20_read_temp（void）{ ds18b20_reset（）;////ds18b20_get_io（index）;
ds18b20_write_byte（SKIP_ROM）; /*skip ROM operation*/ds18b20_write_byte（TEMP_CONVET）; /*start temperature convertion*/
//mdelay（1）;//ds18b20_set_input（index）;//mdelay（1）;mdelay（800）;
ds18b20_reset（）;ds18b20_write_byte（SKIP_ROM）; /*skip ROM operation*/ds18b20_write_byte（READ_TEMP）; /*start read temperature*/data[0]=ds18b20_read_byte（）;data[1]=ds18b20_read_byte（）;printk（"%x,%x  ",data[1],data[0]）;ds18b20_set_output（HIGH）;return 0;}static int ds18b20_open（struct inode * s_node,struct file * s_file）{return 0;}static ssize_t ds18b20_read（struct file *DS1820_file,char * buf, size_t count, loff_t * l）{ds18b20_read_temp（）; buf[0] = data[0];buf[1] = data[1];
return 0;}struct file_operations ds18b20_fops ={.owner  = THIS_MODULE,.open=ds18b20_open, .read=ds18b20_read,};struct class *myclass ;static int __init ds18b20_init（void）{int ret;ret = register_chrdev（char_major,DEV_NAME, &ds18b20_fops）;myclass = class_create（THIS_MODULE,DEV_NAME）;device_create（myclass, NULL, MKDEV（char_major, 0）, NULL, DEV_NAME）;
if（ret<0）{printk（KERN_ALERT "DS18b20 REG FAIL！ "）;}else{printk（KERN_ALERT "MAJOR = %d ",char_major）;}printk（KERN_INFO "Temperature Sensor Driver For ds18b20 "）;ds18b20_reset（）;
return ret;}static void __exit ds18b20_exit（void）{unregister_chrdev（char_major,DEV_NAME）;class_destroy（myclass）;printk（KERN_INFO PFX "ds18b20 dirver removed "）;}module_init（ds18b20_init）;module_exit（ds18b20_exit）;MODULE_AUTHOR（"St.Dickens"）;MODULE_DESCRIPTION（"temperature sensor driver for ds18b20"）;MODULE_LICENSE（"Dual BSD/GPL"）;===================================makefile========================================# Makefile2.6ifneq （$（KERNELRELEASE）,）#kbuild syntax. dependency relationshsip of files and target modules are listed here.obj-m := ds18b20.o elsePWD  := $（shell pwd）KVER = 2.6.27KDIR := /home/dickens/linux-2.6.27all:$（MAKE） -C $（KDIR） M=$（PWD） modulesclean:rm -rf .*.cmd *.o *.mod.c *.ko .tmp_versionsendif==============================随便写了个测试程序=======================================#include "stdio.h"#include "sys/types.h"#include "sys/ioctl.h"#include "stdlib.h"#include "termios.h"#include "sys/stat.h"#include "fcntl.h"#include "sys/time.h"#define DEV_NAME "/dev/ds18b20"void delay（unsigned int time）{while（time>0）time--;}int main（）{int fd;     unsigned char buf[2];     float result;int times=5; //打开设备文件fd=open（DEV_NAME,O_RDWR | O_NDELAY | O_NOCTTY）;if（fd<0）{printf（"Open Device Fail！ "）;return -1;}        //读取当前设备数值else{printf（"OPEND！ "）;}while（times>0）        {            read（fd, buf, 1）;            result = （float）buf[0];            result /= 16;            result += （（float）buf[1] * 16）;            printf（"%.1f `C ", result）;times--;            sleep（5）;        }        close（fd）;}