| commit | author | age | ||
| 13d8a8 | 1 | /********************************************************************************* |
| G | 2 | * Copyright: (C) 2023 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(2023/8/10) | |
| 9 | * Author: Guo Wenxue <guowenxue@gmail.com> | |
| 10 | * ChangeLog: 1, Release initial version on "2023/8/10 12:13:26" | |
| 11 | * | |
| 12 | * Pin connection: | |
| 13 | * | |
| 14 | * DS18B20 Module Raspberry Pi Board | |
| 15 | * VCC <-----> #Pin1(3.3V) | |
| 16 | * DQ <-----> #Pin7(BCM GPIO4) | |
| 17 | * GND <-----> GND | |
| 18 | * | |
| 19 | * /boot/config.txt: | |
| 20 | * | |
| 21 | * dtoverlay=w1-gpio-pullup,gpiopin=4 | |
| 22 | * | |
| 23 | ********************************************************************************/ | |
| 24 | ||
| 25 | ||
| 26 | #include <stdio.h> | |
| 27 | #include <stdlib.h> | |
| 28 | #include <unistd.h> | |
| 29 | #include <fcntl.h> | |
| 30 | #include <dirent.h> | |
| 31 | #include <string.h> | |
| 32 | #include <time.h> | |
| 33 | #include <errno.h> | |
| 34 | ||
| 35 | #include "logger.h" | |
| 36 | ||
| 37 | /* File Content: | |
| 38 | pi@raspberrypi:~/guowenxue $ cat /sys/bus/w1/devices/28-041731f7c0ff/w1_slave | |
| 39 | 3a 01 4b 46 7f ff 0c 10 a5 : crc=a5 YES | |
| 40 | 3a 01 4b 46 7f ff 0c 10 a5 t=19625 | |
| 41 | */ | |
| 42 | ||
| 43 | int ds18b20_get_temperature(float *temp) | |
| 44 | { | |
| 45 | char w1_path[50] = "/sys/bus/w1/devices/"; | |
| 46 | char chip[20]; | |
| 47 | char buf[128]; | |
| 48 | DIR *dirp; | |
| 49 | struct dirent *direntp; | |
| 50 | int fd =-1; | |
| 51 | char *ptr; | |
| 52 | int found = 0; | |
| 53 | ||
| 54 | if( !temp ) | |
| 55 | { | |
| 56 | return -1; | |
| 57 | } | |
| 58 | ||
| 59 | /*+-------------------------------------------------------------------+ | |
| 60 | *| open dierectory /sys/bus/w1/devices to get chipset Serial Number | | |
| 61 | *+-------------------------------------------------------------------+*/ | |
| 62 | if((dirp = opendir(w1_path)) == NULL) | |
| 63 | { | |
| 64 | log_error("opendir error: %s\n", strerror(errno)); | |
| 65 | return -2; | |
| 66 | } | |
| 67 | ||
| 68 | while((direntp = readdir(dirp)) != NULL) | |
| 69 | { | |
| 70 | if(strstr(direntp->d_name,"28-")) | |
| 71 | { | |
| 72 | /* find and get the chipset SN filename */ | |
| 73 | strcpy(chip,direntp->d_name); | |
| 74 | found = 1; | |
| 75 | break; | |
| 76 | } | |
| 77 | } | |
| 78 | closedir(dirp); | |
| 79 | ||
| 80 | if( !found ) | |
| 81 | { | |
| 82 | log_error("Can not find ds18b20 in %s\n", w1_path); | |
| 83 | return -3; | |
| 84 | } | |
| 85 | ||
| 86 | /* get DS18B20 sample file full path: /sys/bus/w1/devices/28-xxxx/w1_slave */ | |
| 87 | strncat(w1_path, chip, sizeof(w1_path)-strlen(w1_path)); | |
| 88 | strncat(w1_path, "/w1_slave", sizeof(w1_path)-strlen(w1_path)); | |
| 89 | ||
| 90 | /* open file /sys/bus/w1/devices/28-xxxx/w1_slave to get temperature */ | |
| 91 | if( (fd=open(w1_path, O_RDONLY)) < 0 ) | |
| 92 | { | |
| 93 | log_error("open %s error: %s\n", w1_path, strerror(errno)); | |
| 94 | return -4; | |
| 95 | } | |
| 96 | ||
| 97 | if(read(fd, buf, sizeof(buf)) < 0) | |
| 98 | { | |
| 99 | log_error("read %s error: %s\n", w1_path, strerror(errno)); | |
| 100 | return -5; | |
| 101 | } | |
| 102 | ||
| 103 | ptr = strstr(buf, "t="); | |
| 104 | if( !ptr ) | |
| 105 | { | |
| 106 | log_error("ERROR: Can not get temperature\n"); | |
| 107 | return -6; | |
| 108 | } | |
| 109 | ||
| 110 | ptr+=2; | |
| 111 | ||
| 112 | /* convert string value to float value */ | |
| 113 | *temp = atof(ptr)/1000; | |
| 114 | ||
| 115 | close(fd); | |
| 116 | ||
| 117 | return 0; | |
| 118 | } | |
