RaspberrPi project source code
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Guo Wenxue
6 days ago f7889e2ceddbc3e15ea4b5377d831f4432169f76
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e30a4c 1 /*********************************************************************************
GW 2  *      Copyright:  (C) 2018 LingYun IoT System Studio
3  *                  All rights reserved.
4  *
5  *       Filename:  ds18b20.c
6  *    Description:  This file is temperature sensor DS18B20 code
7  *
8  *        Version:  1.0.0(2018/10/14)
9  *         Author:  Guo Wenxue <guowenxue@gmail.com>
10  *      ChangeLog:  1, Release initial version on "2018/10/14 12:13:26"
11  *
12  ********************************************************************************/
13
14 #include <stdio.h>
15 #include <stdlib.h>
16 #include <unistd.h>
17 #include <fcntl.h>
18 #include <dirent.h>
19 #include <string.h>
20 #include <time.h>
21 #include <errno.h>
22
23 #include "logger.h"
24
25 /* File Content:
26    pi@raspberrypi:~/guowenxue $ cat /sys/bus/w1/devices/28-041731f7c0ff/w1_slave
27    3a 01 4b 46 7f ff 0c 10 a5 : crc=a5 YES
28    3a 01 4b 46 7f ff 0c 10 a5 t=19625
29  */
30
31 int ds18b20_get_temperature(float *temp)
32 {
33     char            w1_path[50] = "/sys/bus/w1/devices/";
34     char            chip[20];
35     char            buf[128];
36     DIR            *dirp;
37     struct dirent  *direntp;
38     int             fd =-1;
39     char           *ptr;
40     int             found = 0;
41
42     if( !temp )
43     {
44             return -1;
45     }
46
47     /*+-------------------------------------------------------------------+
48      *|  open dierectory /sys/bus/w1/devices to get chipset Serial Number |
49      *+-------------------------------------------------------------------+*/
50     if((dirp = opendir(w1_path)) == NULL)
51     {
52         log_error("opendir '%s' error: %s\n", w1_path, strerror(errno));
53         return -2;
54     }
55
56     while((direntp = readdir(dirp)) != NULL)
57     {
58         if(strstr(direntp->d_name,"28-"))
59         {
60             /* find and get the chipset SN filename */
61             strcpy(chip,direntp->d_name);
62             found = 1;
63         break;
64         }
65     }
66     closedir(dirp);
67
68     if( !found )
69     {
70             log_error("Can not find ds18b20 in %s\n", w1_path);
71             return -3;
72     }
73
74     /* get DS18B20 sample file full path: /sys/bus/w1/devices/28-xxxx/w1_slave */
75     strncat(w1_path, chip, sizeof(w1_path)-strlen(w1_path));
76     strncat(w1_path, "/w1_slave", sizeof(w1_path)-strlen(w1_path));
77
78     /* open file /sys/bus/w1/devices/28-xxxx/w1_slave to get temperature */
79     if( (fd=open(w1_path, O_RDONLY)) < 0 )
80     {
81             log_error("open %s error: %s\n", w1_path, strerror(errno));
82             return -4;
83     }
84
85     if(read(fd, buf, sizeof(buf)) < 0)
86     {
87             log_error("read %s error: %s\n", w1_path, strerror(errno));
88             return -5;
89     }
90
91     ptr = strstr(buf, "t=");
92     if( !ptr )
93     {
94             log_error("ERROR: Can not get temperature\n");
95             return -6;
96     }
97
98     ptr+=2;
99
100     /* convert string value to float value */
101     *temp = atof(ptr)/1000;
102
103     close(fd);
104
105     return 0;
106 }