147 lines
3.4 KiB
C
147 lines
3.4 KiB
C
/*
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* ds18b20.c:
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* Extend wiringPi with the DS18B20 1-Wire temperature sensor.
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* This is used in the Pi Weather Station and many other places.
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* Copyright (c) 2016 Gordon Henderson
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***********************************************************************
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* This file is part of wiringPi:
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* https://projects.drogon.net/raspberry-pi/wiringpi/
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*
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* wiringPi is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* wiringPi is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with wiringPi.
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* If not, see <http://www.gnu.org/licenses/>.
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***********************************************************************
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <string.h>
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#include <malloc.h>
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#include <ctype.h>
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#include "wiringPi.h"
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#include "ds18b20.h"
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#define W1_PREFIX "/sys/bus/w1/devices/28-"
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#define W1_POSTFIX "/w1_slave"
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/*
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* myAnalogRead:
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*********************************************************************************
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*/
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static int myAnalogRead (struct wiringPiNodeStruct *node, int pin)
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{
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int chan = pin - node->pinBase ;
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int fd = node->fd ;
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char buffer [4096] ;
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char *p ;
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int temp, sign ;
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if (chan != 0)
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return -9999 ;
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// Rewind the file - we're keeping it open to keep things going
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// smoothly
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lseek (fd, 0, SEEK_SET) ;
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// Read the file - we know it's only a couple of lines, so this ought to be
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// more than enough
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if (read (fd, buffer, 4096) <= 0) // Read nothing, or it failed in some odd way
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return -9998 ;
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// Look for YES, then t=
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if (strstr (buffer, "YES") == NULL)
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return -9997 ;
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if ((p = strstr (buffer, "t=")) == NULL)
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return -9996 ;
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// p points to the 't', so we skip over it...
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p += 2 ;
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// and extract the number
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// (without caring about overflow)
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if (*p == '-') // Negative number?
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{
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sign = -1 ;
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++p ;
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}
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else
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sign = 1 ;
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temp = 0 ;
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while (isdigit (*p))
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{
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temp = temp * 10 + (*p - '0') ;
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++p ;
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}
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// We know it returns temp * 1000, but we only really want temp * 10, so
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// do a bit of rounding...
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temp = (temp + 50) / 100 ;
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return temp * sign ;
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}
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/*
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* ds18b20Setup:
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* Create a new instance of a DS18B20 temperature sensor.
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*********************************************************************************
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*/
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int ds18b20Setup (const int pinBase, const char *deviceId)
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{
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int fd ;
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struct wiringPiNodeStruct *node ;
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char *fileName ;
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// Allocate space for the filename
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if ((fileName = malloc (strlen (W1_PREFIX) + strlen (W1_POSTFIX) + strlen (deviceId) + 1)) == NULL)
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return FALSE ;
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sprintf (fileName, "%s%s%s", W1_PREFIX, deviceId, W1_POSTFIX) ;
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fd = open (fileName, O_RDONLY) ;
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free (fileName) ;
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if (fd < 0)
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return FALSE ;
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// We'll keep the file open, to make access a little faster
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// although it's very slow reading these things anyway )-:
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node = wiringPiNewNode (pinBase, 1) ;
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node->fd = fd ;
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node->analogRead = myAnalogRead ;
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return TRUE ;
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}
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