wiringPi_Blueberry/wiringPi/ds18b20.c
2023-08-11 15:53:17 +08:00

147 lines
3.4 KiB
C

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