app-ds18b20.c#include <linux/init.h> #include <linux/module.h> #include <linux/delay.h> #include <linux/kernel.h> #include <linux/moduleparam.h> #include <linux/init.h> #include <linux/types.h> #include <linux/fs.h> #include <mach/regs-gpio.h> #include <mach/hardware.h> #include <linux/cdev.h> #include <asm/uaccess.h> #include <linux/errno.h> #include <linux/gpio.h> #include <linux/device.h> /* 相關引腳定義,方便以後移植 */ #define DQ S3C2410_GPF(3) #define CFG_IN S3C2410_GPIO_INPUT #define CFG_OUT S3C2410_GPIO_OUTPUT // ds18b20主次設備號（動態分配） static int ds18b20_major = 0; static int ds18b20_minor = 0; static int ds18b20_nr_devs = 1; // 定義設備類型 static struct ds18b20_device { struct cdev cdev; }; struct ds18b20_device *ds18b20_devp; /*設備結構體指針 */ static struct class *ds18b20_class; static struct class_device *ds18b20_class_dev; /* 函數聲明 */ static int ds18b20_open(struct inode *inode, struct file *filp); static int ds18b20_init(void); static void write_byte(unsigned char data); static unsigned char read_byte(void); static ssize_t ds18b20_read(struct file *filp, char __user * buf, size_t count, loff_t * f_pos); void ds18b20_setup_cdev(struct ds18b20_device *dev, int index); static int ds18b20_open(struct inode *inode, struct file *filp) { int flag = 0; flag = ds18b20_init(); if (flag & 0x01) { printk(KERN_WARNING "open ds18b20 failed\n"); return -1; } printk(KERN_NOTICE "open ds18b20 successful\n"); return 0; } static int ds18b20_init(void) { int retval = 0; s3c2410_gpio_cfgpin(DQ, CFG_OUT); s3c2410_gpio_pullup(DQ, 0); s3c2410_gpio_setpin(DQ, 1); udelay(2); s3c2410_gpio_setpin(DQ, 0); // 拉低ds18b20總線，復位ds18b20 udelay(500); // 保持復位電平500us s3c2410_gpio_setpin(DQ, 1); // 釋放ds18b20總線 udelay(60); // 若復位成功，ds18b20發出存在脈衝（低電平，持續60~240us） s3c2410_gpio_cfgpin(DQ, CFG_IN); retval = s3c2410_gpio_getpin(DQ); udelay(500); s3c2410_gpio_cfgpin(DQ, CFG_OUT); s3c2410_gpio_pullup(DQ, 0); s3c2410_gpio_setpin(DQ, 1); // 釋放總線 return retval; } static void write_byte(unsigned char data) { int i = 0; s3c2410_gpio_cfgpin(DQ, CFG_OUT); s3c2410_gpio_pullup(DQ, 1); for (i = 0; i < 8; i++) { // 總線從高拉至低電平時，就產生寫時隙 s3c2410_gpio_setpin(DQ, 1); udelay(2); s3c2410_gpio_setpin(DQ, 0); s3c2410_gpio_setpin(DQ, data & 0x01); udelay(60); data >>= 1; } s3c2410_gpio_setpin(DQ, 1); // 重新釋放ds18b20總線 } static unsigned char read_byte(void) { int i; unsigned char data = 0; for (i = 0; i < 8; i++) { // 總線從高拉至低，只需維持低電平17ts，再把總線拉高，就產生讀時隙 s3c2410_gpio_cfgpin(DQ, CFG_OUT); s3c2410_gpio_pullup(DQ, 0); s3c2410_gpio_setpin(DQ, 1); udelay(2); s3c2410_gpio_setpin(DQ, 0); udelay(2); s3c2410_gpio_setpin(DQ, 1); udelay(8); data >>= 1; s3c2410_gpio_cfgpin(DQ, CFG_IN); if (s3c2410_gpio_getpin(DQ)) data |= 0x80; udelay(50); } s3c2410_gpio_cfgpin(DQ, CFG_OUT); s3c2410_gpio_pullup(DQ, 0); s3c2410_gpio_setpin(DQ, 1); // 釋放ds18b20總線 return data; } static ssize_t ds18b20_read(struct file *filp, char __user * buf, size_t count, loff_t * f_pos) { int flag; unsigned long err; unsigned char result[2] = { 0x00, 0x00 }; //struct ds18b20_device *dev = filp->private_data; flag = ds18b20_init(); if (flag & 0x01) { printk(KERN_WARNING "ds18b20 init failed\n"); return -1; } write_byte(0xcc); write_byte(0x44); flag = ds18b20_init(); if (flag & 0x01) return -1; write_byte(0xcc); write_byte(0xbe); result[0] = read_byte(); // 溫度低八位 result[1] = read_byte(); // 溫度高八位 err = copy_to_user(buf, &result, sizeof(result)); return err ? -EFAULT : min(sizeof(result), count); } static struct file_operations ds18b20_dev_fops = { .owner = THIS_MODULE, .open = ds18b20_open, .read = ds18b20_read, }; void ds18b20_setup_cdev(struct ds18b20_device *dev, int index) { int err, devno = MKDEV(ds18b20_major, ds18b20_minor + index); cdev_init(&dev->cdev, &ds18b20_dev_fops); dev->cdev.owner = THIS_MODULE; err = cdev_add(&(dev->cdev), devno, 1); if (err) { printk(KERN_NOTICE "ERROR %d add ds18b20\n", err); } } static int __init ds18b20_dev_init(void) { int result; dev_t dev = 0; dev = MKDEV(ds18b20_major, ds18b20_minor); if (ds18b20_major) { result = register_chrdev_region(dev, ds18b20_nr_devs, "ds18b20"); } else { result = alloc_chrdev_region(&dev, ds18b20_minor, ds18b20_nr_devs, "ds18b20"); ds18b20_major = MAJOR(dev); } if (result < 0) { printk(KERN_WARNING "ds18b20: failed to get major\n"); return result; } /* 爲新設備分配內存和初始化 */ ds18b20_devp = kmalloc(sizeof(struct ds18b20_device), GFP_KERNEL); if (!ds18b20_devp) { /*申請失敗 */ result = -ENOMEM; goto fail_malloc; } memset(ds18b20_devp, 0, sizeof(struct ds18b20_device)); ds18b20_setup_cdev(ds18b20_devp, 0); /* 自動創建設備節點 */ ds18b20_class = class_create(THIS_MODULE, "ds18b20_sys_class"); if (IS_ERR(ds18b20_class)) return PTR_ERR(ds18b20_class); ds18b20_class_dev = device_create(ds18b20_class, NULL, MKDEV(ds18b20_major, 0), NULL, "ds18b20"); if (unlikely(IS_ERR(ds18b20_class_dev))) return PTR_ERR(ds18b20_class_dev); return 0; fail_malloc: unregister_chrdev_region(dev, 1); return result; } static void __exit ds18b20_dev_exit(void) { cdev_del(&ds18b20_devp->cdev); /*註銷cdev */ kfree(ds18b20_devp); /*釋放設備結構體內存 */ unregister_chrdev_region(MKDEV(ds18b20_major, 0), ds18b20_nr_devs); /*釋放設備號 */ device_unregister(ds18b20_class_dev); class_destroy(ds18b20_class); } module_init(ds18b20_dev_init); module_exit(ds18b20_dev_exit); MODULE_LICENSE("Dual BSD/GPL"); MODULE_AUTHOR("[email protected]");
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/ioctl.h>
// 函數聲明
void ds18b20_delay(int i);
int main()
{
int fd, i;
unsigned char result[2]; // 從ds18b20讀出的結果，result[0]存放低八位
unsigned char integer_value = 0;
float decimal_value = 0; // 溫度數值,decimal_value爲小數部分的值
float temperature = 0;
fd = open("/dev/ds18b20", 0);
if (fd < 0)
{
perror("open device failed\n");
exit(1);
}
while (1)
{
i++;
read(fd, &result, sizeof(result));
integer_value = ((result[0] & 0xf0) >> 4) | ((result[1] & 0x07) << 4);
// 精確到0.25度
decimal_value = 0.5 * ((result[0] & 0x0f) >> 3) + 0.25 * ((result[0] & 0x07) >> 2);
temperature = (float)integer_value + decimal_value;
printf("Current Temperature:%6.2f\n", temperature);
ds18b20_delay(500);
}
}
void ds18b20_delay(int i)
{
int j, k;
for (j = 0; j < i; j++)
for (k = 0; k < 50000; k++) ;
}
Makefile
ifneq ($(KERNELRELEASE),) obj-m := ds18b20_drv.o else KDIR := /home/youshan/linux-2.6.32.2 MYAPP := app-ds18b20 all: make -C $(KDIR) M=$(PWD) modules ARCH=arm CROSS_COMPILE=arm-linux- arm-linux-gcc $(MYAPP).c -o $(MYAPP) clean: rm -f *.ko *.o *.mod.o *.mod.c *.symvers modul* rm -f $(MYAPP) endif
運行結果：
[root@ShiGuang home]# [root@ShiGuang home]#./app-ds18b20 open ds18b20 successful Current Temperature: 23.50 Current Temperature: 23.50 Current Temperature: 23.25 Current Temperature: 23.50 Current Temperature: 23.50 Current Temperature: 23.50 ^C [root@ShiGuang home]#