mini2440的ds18b20驱动和测试程序

一步一步的在昨天终于把基于 mini2440的ds18b20的驱动编译成功了。其中最大的问题居然是18b20插反了，导致我研究了一天时间最后还是别人告诉我才发现反了。百度图片不可信啊，居然有错图，以后一定要长记性，去下官方的datasheet。呵呵

下面记录下自己的编译过程。

首先是从网上找了个18b20的驱动下载下来了，因为18b20是个技术很成熟的芯片，因此网上资料很多。我下载的代码如下：#include <linux/config.h>#include <linux/module.h>#include <linux/kernel.h>#include <linux/sched.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/devfs_fs_kernel.h>#include <linux/miscdevice.h>#include <asm/irq.h>#include <asm/arch/regs-gpio.h>#include <asm/hardware.h>#include <asm/uaccess.h>#define DEVICE_NAME "DS18B20"#define DS18B20_MAJOR 242#define DS_PIN S3C2410_GPF0#define OUT S3C2410_GPF0_OUTP#define IN S3C2410_GPF0_INP#define DIS_UP 1#define EN_UP 0#define Search 0x00F0#define Read_ROM 0x0033 //just for one#define Skip_ROM 0x00CC #define Convert 0x0044#define Write 0x004E //TH---TL---Config#define Read 0x00BE#define bit_9 0x001F#define bit_10 0x003F#define bit_11 0x005F#define bit_12 0x007F#define uint16 unsigned int//unsigned int ROM_DATA[8];void usdelay(unsigned int i) //延时 i us 对于不同系统可能会有所差别,请适当修改{unsigned int j;for(i=i;i>0;i--) for(j=90;j>0;j--);}void msdelay(unsigned int i) //延时 i us{for(i=i;i>0;i--) usdelay(1000);}void SetL(void){s3c2410_gpio_cfgpin(DS_PIN,OUT);s3c2410_gpio_setpin(DS_PIN,0);}void SetH(void){s3c2410_gpio_cfgpin(DS_PIN,OUT);s3c2410_gpio_setpin(DS_PIN,1);}unsigned int Read_DS(void){unsigned int i;s3c2410_gpio_cfgpin(DS_PIN,IN);s3c2410_gpio_pullup(DS_PIN,EN_UP);__asm("nop");__asm("nop");__asm("nop");i=s3c2410_gpio_getpin(DS_PIN);if(i!=0) i=1;return i;}unsigned int ds_start(void){unsigned int flag=1;int err=0;SetL();usdelay(500); //560SetH();usdelay(1);while(Read_DS()!=0){// printk(DEVICE_NAME "Wait..../n"); usdelay(5); err++; if(err==20) { printk(DEVICE_NAME "start fail/n"); return -1; }}// printk(DEVICE_NAME "start sucess/n");flag=0;SetH();usdelay(400);return flag;}void ds_send(unsigned int uidata){unsigned int i;for(i=0;i<8;i++){ SetL(); if((uidata&1)!=0) { usdelay(3); //3 SetH(); usdelay(80); } else { usdelay(80); SetH(); usdelay(5); // } uidata>>=1;}}unsigned int ds_read(void){unsigned int uidata=0;unsigned int i;for(i=0;i<8;i++){ SetL(); usdelay(4); //2 3 SetH(); usdelay(7); //1 2 3 4 5(e) if(Read_DS()==1) uidata+=0x0100; uidata>>=1; SetH(); usdelay(65);}return uidata; }void ds_init(unsigned int TH,unsigned int TL,unsigned int bit_nmb){SetH();usdelay(80);if(ds_start()==0){ ds_send(Skip_ROM); //复位 ds_send(Write); //跳过ROM匹配 ds_send(TH); //TH ds_send(TL); //TL ds_send(bit_nmb); //转换位数}}unsigned int read_tem(void){unsigned int th,tl;int err=0;ds_init(100,0,bit_12);th=tl=0; ds_start();ds_start();ds_start();ds_send(Skip_ROM);ds_send(Convert);msdelay(50);while(Read_DS()==0){// printk(DEVICE_NAME "Convert..../n"); msdelay(50); err++; if(err==10) { printk(DEVICE_NAME "convert fail/n"); return -1; }}ds_start();ds_start();ds_send(Skip_ROM);ds_send(Read);tl=ds_read();th=ds_read();ds_start();ds_start();th<<=8;tl|=th;return tl;}static int ds18b20_ioctl(struct inode *inode, struct file *file, unsigned int cmd,unsigned long arg){return 0;}static ssize_t ds18b20_read(struct file *pFile, uint16 __user *pData, size_t count, loff_t *off ){ uint16 tmp,ret; tmp =read_tem(); ret=copy_to_user(pData, &tmp, sizeof(tmp)); //将读取得的DS18B20数值复制到用户区if(ret>0){ printk("copy data failed/n"); return -1;} return 0;}static struct file_operations ds18b20_fops = {.owner = THIS_MODULE,.ioctl = ds18b20_ioctl,.read = ds18b20_read,};static int __init ds18b20_init(void){int ret;ret = register_chrdev(DS18B20_MAJOR, DEVICE_NAME, &ds18b20_fops);if (ret < 0) { printk(DEVICE_NAME " can't register major number/n"); return ret;}devfs_mk_cdev(MKDEV(DS18B20_MAJOR, 0), S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP, DEVICE_NAME);s3c2410_gpio_cfgpin(DS_PIN, OUT);s3c2410_gpio_setpin(DS_PIN, 1);//printk(DEVICE_NAME " initialized/n");return 0;}static void __exit ds18b20_exit(void){devfs_remove(DEVICE_NAME);unregister_chrdev(DS18B20_MAJOR, DEVICE_NAME);printk(DEVICE_NAME " rmmodule/n");}module_init(ds18b20_init);module_exit(ds18b20_exit);MODULE_AUTHOR("[e-mail]"); // 驱动程序的作者MODULE_DESCRIPTION("DS18B20 Driver"); // 一些描述信息MODULE_LICENSE("GPL"); // 遵循的协议 

我只改了引脚和主设备号。其他的都没改。

按照之前的帖子编译，编译成功后出现*.ko文件。

建立nfs服务器，

mknod /dev/DS18B20 c 242 0

insmod ds18b20.ko

两条命令如果都没有错误自少说明驱动的方法没有问题，就看驱动本身有没有错误了。

连线，18b20有三根线，把平面对着自己，左手边起为地，数据，正。

在数据和正之间要加一个4-10k的电阻，我加的是4.7K的。开发板插的是一个正，地，和gpf0端口。fpf0端口在con4的靠着滑动电阻的第五根线。正是第一根，地是第二跟。

之后编译测试程序，如下：

#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/ioctl.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <sys/select.h>#include <sys/time.h>#include <errno.h>#define K 0.0625int main(void){ int fd = -1; char count = 5; unsigned int tmp = 0;float res=0; fd = open("/dev/DS18B20", 0); if(fd < 0) { perror("Can't open /dev/DS18B20 /n"); exit(1); } printf("open ds18b20 success /n");while(1){ read(fd, &tmp , sizeof(tmp));res=tmp*K;printf("the currently temperature is %f/n",res);sleep(1);}close(fd); return 0;} 

编译后运行，如果没有什么线插错的情况下应该就能正常显示温度了。呵呵～