Ds1621.c

/* Test DS1621 sur interface I2C de type philips (port //) (6/2004) */
/* Affichage de la t° tout les 10s */
/* Par domos domos78<at>free<point>fr */
 
/* 8/4/2007 */
/* Test avec accés device i2c sans fonction smbus (i2c.h). */
/* Exemple inspiré de Linux Magazine HS23 (Electronique). */
/* gcc -Wall -o ds1621 -O3 ds1621_3.c */
 
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
 
#define I2C_SLAVE       0x0703  /* Change slave address                 */
 
static int i2c_fd ;
int res ;
 
#define DEVICE "/dev/i2cpar"            // Lien vers /dev/i2c-x
#define ds1621_addr 0x9E >> 1           // Adr. i2c DS1621 (A0, A1, A2 à Vcc)
 
 
/*------------------------------------------------------------------------------*/
/* Fonctions i2c                                                                */
/*------------------------------------------------------------------------------*/
void i2c_init()
{
        i2c_fd = open( DEVICE, O_RDWR );
        if ( i2c_fd < 0 )
        {
                printf("Erreur, impossible d'ouvrir %s", DEVICE );
                exit(1) ;
        }
}
 
//-----------------------------------------------------------------------------
void SelectSlave(unsigned char slaveaddr)
{
        int res ;
        res = ioctl(i2c_fd, I2C_SLAVE, slaveaddr) ;
        //printf("Code retour 'SelectSlave': %d\n", res) ;
        if ( res < 0 )
        {
                printf("Erreur, impossible de sélectionner le composant i2c à l'adresse 0x%x: '%s'",  slaveaddr, strerror(errno));
                close ( i2c_fd );
                exit(1) ;
        }
}
 
/*------------------------------------------------------------------------------*/
/* Fonctions DS1621                                                             */
/*------------------------------------------------------------------------------*/
int i2c_init_ds1621(unsigned char addr)
{
        int res ;
        char buff[10] ;
 
        SelectSlave(addr) ;
        buff[0] = 0xAC ;
        buff[1] = 0x01 ;
        res = write( i2c_fd, buff, 2 );
        if ( res < 0 )
        {
                printf("Erreur init DS1621 addr 0x%x: '%s', Abandon programme !", addr, strerror(errno));
                close ( i2c_fd );
                exit(1) ;
        }
        /* start temperature conversion */
        errno = 0 ;      
        buff[0] = 0xEE ;
        write( i2c_fd, buff, 1 );
        sleep(1) ;
        return 1 ;
}
 
//-----------------------------------------------------------------------------
double i2c_gettemp_ds1621(unsigned char addr)
{
        int k, count, slope, temp;
        char buff[10] ;
        int res ;
 
        SelectSlave(addr) ;
        /* stop conversion */
        errno = 0 ;      
        buff[0] = 0x22 ;
        res = write( i2c_fd, buff, 1 );
        if ( res < 0 )
        {
                printf("Erreur écriture DS1621 addr 0x%x: '%s'", ds1621_addr, strerror(errno));
                return 255 ;    // 255 car retourne normalement la t°.
        }
        else
        {
                /* Temperature reading (1 Celsius degree precision) */
                buff[0] = 0xAA ;
                write( i2c_fd, buff, 1 );
                read(i2c_fd, buff, 1) ;
                temp = buff[0] ;
                /* Counter reading (fraction of degree) ) */
                buff[0] = 0xA8 ;
                write( i2c_fd, buff, 1 );
                read(i2c_fd, buff, 1) ;
                count = buff[0] ;
                /* slope reading */
                buff[0] = 0xA9 ;
                write( i2c_fd, buff, 1 );
                read(i2c_fd, buff, 1) ;
                slope = buff[0] ;
                k = temp;
                if (slope != 0) 
                {
                        k = temp*100-25+(100*(slope-count))/slope;
                }
                //printf("Temp DS1621_1: %2.1f°\n", (float)k/100) ;
                /* start temperature conversion */
                buff[0] = 0xEE ;
                write( i2c_fd, buff, 1 );
                return (float)k/100 ;
        }
}
 
/*------------------------------------------------------------------------------*/
int main ( int argc, char ** argv )
{
        double temp_1 ;
 
        // Init i2c.
        i2c_init() ;
 
        // Init ds1621.
        i2c_init_ds1621(ds1621_addr) ;
 
        while (1)
        {   
                temp_1 = i2c_gettemp_ds1621(ds1621_addr) ;      // Lit t° ds1621.
                printf("Temp: %2.1f°\n", temp_1) ;      
                sleep(10) ;     
        }
}
 
/*------------------------------------------------------------------------------*/