DS18B20

Nous allons utiliser les sondes de températures DS18B20 sur ,le bus One Wire du raspberry Pi

le GPIO4 est ici notre bus , il faut juste ajouter la résistance 4,7kOhms en Pull UP

pi@raspberrypi:~/Works/ds18b20 $ ls /sys/bus/w1/devices/

28-000008dafdc6  28-0000096a78d5  w1_bus_master1

pi@raspberrypi:~/Works/ds18b20 $ 

/* code exemple de lecture de 2 sondes de température sur le BUS 1W */

#include <stdlib.h>

#include <stdio.h>

#include <wiringPi.h>

#include <ds18b20.h>

int main(int argc, char ** argv)

{

int temp;

float sonde1,sonde2;

ds18b20Setup (100, "000008dafdc6") ;

ds18b20Setup (101, "0000096a78d5") ;

temp = analogRead (100) ;

sonde1=(float)temp/10;

temp = analogRead (101);

sonde2= (float)temp/10;

printf("Temperature sonde 1: %2.2f \n", sonde1);

printf("Temperature sonde 2: %2.2f \n", sonde2);

return EXIT_SUCCESS;

}

pi@raspberrypi:~/Works/ds18b20 $ gcc main.c -o main -lwiringPi

pi@raspberrypi:~/Works/ds18b20 $ ./main 

Temperature sonde 1: 20.50 

Temperature sonde 2: 20.10 

pi@raspberrypi:~/Works/ds18b20 $ 

on retrouve sur Github les sources

ds18b20.h

*

 * bmp180.h:

 * Extend wiringPi with the BMP180 I2C Pressure and Temperature

 * sensor.

 * 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/>.

 ***********************************************************************

 */

#ifdef __cplusplus

extern "C" {

#endif

extern int ds18b20Setup (const int pinBase, const char *serialNum) ;

#ifdef __cplusplus

}

#endif

ds18b20.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 ;

}