mini2440上DS18B20的驅動程序（含簡單測試）

ds18b20_drv.c

[cpp]

1. #include <linux/init.h>
2. #include <linux/module.h>
3. #include <linux/delay.h>
4. #include <linux/kernel.h>
5. #include <linux/moduleparam.h>
6. #include <linux/init.h>
7. #include <linux/types.h>
8. #include <linux/fs.h>
9. #include <mach/regs-gpio.h>
10. #include <mach/hardware.h>
11. #include <linux/cdev.h>
12. #include <asm/uaccess.h>
13. #include <linux/errno.h>
14. #include <linux/gpio.h>
15. #include <linux/device.h>
17. /* 相關引腳定義,方便以後移植 */
18. #define DQ S3C2410_GPF(3)
19. #define CFG_IN S3C2410_GPIO_INPUT
20. #define CFG_OUT S3C2410_GPIO_OUTPUT
22. // ds18b20主次設備號（動態分配）
23. static int ds18b20_major = 0;
24. static int ds18b20_minor = 0;
25. static int ds18b20_nr_devs = 1;
27. // 定義設備類型
28. static struct ds18b20_device
29. {
30. struct cdev cdev;
31. };
33. struct ds18b20_device *ds18b20_devp; /*設備結構體指針 */
35. static struct class *ds18b20_class;
36. static struct class_device *ds18b20_class_dev;
38. /* 函數聲明 */
39. static int ds18b20_open(struct inode *inode, struct file *filp);
40. static int ds18b20_init(void);
41. static void write_byte(unsigned char data);
42. static unsigned char read_byte(void);
43. static ssize_t ds18b20_read(struct file *filp, char __user * buf, size_t count, loff_t * f_pos);
44. void ds18b20_setup_cdev(struct ds18b20_device *dev, int index);
46. static int ds18b20_open(struct inode *inode, struct file *filp)
47. {
48. int flag = 0;
50. flag = ds18b20_init();
51. if (flag & 0x01)
52. {
53. printk(KERN_WARNING "open ds18b20 failed\n");
54. return -1;
55. }
56. printk(KERN_NOTICE "open ds18b20 successful\n");
57. return 0;
58. }
60. static int ds18b20_init(void)
61. {
62. int retval = 0;
64. s3c2410_gpio_cfgpin(DQ, CFG_OUT);
65. s3c2410_gpio_pullup(DQ, 0);
67. s3c2410_gpio_setpin(DQ, 1);
68. udelay(2);
69. s3c2410_gpio_setpin(DQ, 0); // 拉低ds18b20總線，復位ds18b20
70. udelay(500); // 保持復位電平500us
72. s3c2410_gpio_setpin(DQ, 1); // 釋放ds18b20總線
73. udelay(60);
75. // 若復位成功，ds18b20發出存在脈沖（低電平，持續60~240us）
76. s3c2410_gpio_cfgpin(DQ, CFG_IN);
77. retval = s3c2410_gpio_getpin(DQ);
79. udelay(500);
80. s3c2410_gpio_cfgpin(DQ, CFG_OUT);
81. s3c2410_gpio_pullup(DQ, 0);
82. s3c2410_gpio_setpin(DQ, 1); // 釋放總線
84. return retval;
85. }
87. static void write_byte(unsigned char data)
88. {
89. int i = 0;
91. s3c2410_gpio_cfgpin(DQ, CFG_OUT);
92. s3c2410_gpio_pullup(DQ, 1);
94. for (i = 0; i < 8; i++)
95. {
96. // 總線從高拉至低電平時，就產生寫時隙
97. s3c2410_gpio_setpin(DQ, 1);
98. udelay(2);
99. s3c2410_gpio_setpin(DQ, 0);
100. s3c2410_gpio_setpin(DQ, data & 0x01);
101. udelay(60);
102. data >>= 1;
103. }
104. s3c2410_gpio_setpin(DQ, 1); // 重新釋放ds18b20總線
105. }
107. static unsigned char read_byte(void)
108. {
109. int i;
110. unsigned char data = 0;
112. for (i = 0; i < 8; i++)
113. {
114. // 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
115. s3c2410_gpio_cfgpin(DQ, CFG_OUT);
116. s3c2410_gpio_pullup(DQ, 0);
117. s3c2410_gpio_setpin(DQ, 1);
118. udelay(2);
119. s3c2410_gpio_setpin(DQ, 0);
120. udelay(2);
121. s3c2410_gpio_setpin(DQ, 1);
122. udelay(8);
123. data >>= 1;
124. s3c2410_gpio_cfgpin(DQ, CFG_IN);
125. if (s3c2410_gpio_getpin(DQ))
126. data |= 0x80;
127. udelay(50);
128. }
129. s3c2410_gpio_cfgpin(DQ, CFG_OUT);
130. s3c2410_gpio_pullup(DQ, 0);
131. s3c2410_gpio_setpin(DQ, 1); // 釋放ds18b20總線
132. return data;
133. }
135. static ssize_t ds18b20_read(struct file *filp, char __user * buf, size_t count, loff_t * f_pos)
136. {
137. int flag;
138. unsigned long err;
139. unsigned char result[2] = { 0x00, 0x00 };
140. //struct ds18b20_device *dev = filp->private_data;
142. flag = ds18b20_init();
143. if (flag & 0x01)
144. {
145. printk(KERN_WARNING "ds18b20 init failed\n");
146. return -1;
147. }
149. write_byte(0xcc);
150. write_byte(0x44);
152. flag = ds18b20_init();
153. if (flag & 0x01)
154. return -1;
156. write_byte(0xcc);
157. write_byte(0xbe);
159. result[0] = read_byte(); // 溫度低八位
160. result[1] = read_byte(); // 溫度高八位
162. err = copy_to_user(buf, &result, sizeof(result));
163. return err ? -EFAULT : min(sizeof(result), count);
164. }
166. static struct file_operations ds18b20_dev_fops = {
167. .owner = THIS_MODULE,
168. .open = ds18b20_open,
169. .read = ds18b20_read,
170. };
172. void ds18b20_setup_cdev(struct ds18b20_device *dev, int index)
173. {
174. int err, devno = MKDEV(ds18b20_major, ds18b20_minor + index);
176. cdev_init(&dev->cdev, &ds18b20_dev_fops);
177. dev->cdev.owner = THIS_MODULE;
178. err = cdev_add(&(dev->cdev), devno, 1);
179. if (err)
180. {
181. printk(KERN_NOTICE "ERROR %d add ds18b20\n", err);
182. }
183. }
185. static int __init ds18b20_dev_init(void)
186. {
187. int result;
188. dev_t dev = 0;
190. dev = MKDEV(ds18b20_major, ds18b20_minor);
192. if (ds18b20_major)
193. {
194. result = register_chrdev_region(dev, ds18b20_nr_devs, "ds18b20");
195. }
196. else
197. {
198. result = alloc_chrdev_region(&dev, ds18b20_minor, ds18b20_nr_devs, "ds18b20");
199. ds18b20_major = MAJOR(dev);
200. }
201. if (result < 0)
202. {
203. printk(KERN_WARNING "ds18b20: failed to get major\n");
204. return result;
205. }
207. /* 為新設備分配內存和初始化 */
208. ds18b20_devp = kmalloc(sizeof(struct ds18b20_device), GFP_KERNEL);
209. if (!ds18b20_devp)
210. { /*申請失敗 */
211. result = -ENOMEM;
212. goto fail_malloc;
213. }
214. memset(ds18b20_devp, 0, sizeof(struct ds18b20_device));
216. ds18b20_setup_cdev(ds18b20_devp, 0);
218. /* 自動創建設備節點 */
219. ds18b20_class = class_create(THIS_MODULE, "ds18b20_sys_class");
220. if (IS_ERR(ds18b20_class))
221. return PTR_ERR(ds18b20_class);
223. ds18b20_class_dev =
224. device_create(ds18b20_class, NULL, MKDEV(ds18b20_major, 0), NULL, "ds18b20");
225. if (unlikely(IS_ERR(ds18b20_class_dev)))
226. return PTR_ERR(ds18b20_class_dev);
228. return 0;
230. fail_malloc:
231. unregister_chrdev_region(dev, 1);
232. return result;
233. }
235. static void __exit ds18b20_dev_exit(void)
236. {
237. cdev_del(&ds18b20_devp->cdev); /*注銷cdev */
238. kfree(ds18b20_devp); /*釋放設備結構體內存 */
239. unregister_chrdev_region(MKDEV(ds18b20_major, 0), ds18b20_nr_devs); /*釋放設備號 */
240. device_unregister(ds18b20_class_dev);
241. class_destroy(ds18b20_class);
242. }
244. module_init(ds18b20_dev_init);
245. module_exit(ds18b20_dev_exit);
246. MODULE_LICENSE("Dual BSD/GPL");
247. MODULE_AUTHOR("[email protected]");

[cpp]

1. #include <stdio.h>
2. #include <stdlib.h>
3. #include <unistd.h>
4. #include <linux/ioctl.h>
6. // 函數聲明
7. void ds18b20_delay(int i);
9. int main()
10. {
11. int fd, i;
12. unsigned char result[2]; // 從ds18b20讀出的結果，result[0]存放低八位
13. unsigned char integer_value = 0;
14. float decimal_value = 0; // 溫度數值,decimal_value為小數部分的值
15. float temperature = 0;
17. fd = open("/dev/ds18b20", 0);
18. if (fd < 0)
19. {
20. perror("open device failed\n");
21. exit(1);
22. }
23. while (1)
24. {
25. i++;
26. read(fd, &result, sizeof(result));
27. integer_value = ((result[0] & 0xf0) >> 4) | ((result[1] & 0x07) << 4);
28. // 精確到0.25度
29. decimal_value = 0.5 * ((result[0] & 0x0f) >> 3) + 0.25 * ((result[0] & 0x07) >> 2);
30. temperature = (float)integer_value + decimal_value;
31. printf("Current Temperature:%6.2f\n", temperature);
33. ds18b20_delay(500);
34. }
35. }
37. void ds18b20_delay(int i)
38. {
39. int j, k;
40. for (j = 0; j < i; j++)
41. for (k = 0; k < 50000; k++) ;
42. }

[cpp]

1. ifneq ($(KERNELRELEASE),)
2. obj-m := ds18b20_drv.o
4. else
5. KDIR := /home/youshan/linux-2.6.32.2
6. MYAPP := app-ds18b20
8. all:
9. make -C $(KDIR) M=$(PWD) modules ARCH=arm CROSS_COMPILE=arm-linux-
10. arm-linux-gcc $(MYAPP).c -o $(MYAPP)
12. clean:
13. rm -f *.ko *.o *.mod.o *.mod.c *.symvers modul*
14. rm -f $(MYAPP)
16. endif

運行結果：

[cpp]

1. [[email protected] home]#
2. [[email protected] home]#./app-ds18b20
3. open ds18b20 successful
4. Current Temperature: 23.50
5. Current Temperature: 23.50
6. Current Temperature: 23.25
7. Current Temperature: 23.50
8. Current Temperature: 23.50
9. Current Temperature: 23.50
10. ^C
11. [[email protected] home]#