mcp23017 i2c a la C...... TEST

#include <stdio.h>
#include <stdlib.h>     /* exit, EXIT_FAILURE */
#include <fcntl.h>
#include <linux/i2c-dev.h>
#include <errno.h>

#include <sys/ioctl.h>
#include <unistd.h>

#define I2C_ADDR 0x20
#define DEV_I2C "/dev/i2c-0"
/*--------------------------------------------------------------------*/
int I2COpen(){//Return fd
    int fd;

    fd = open(DEV_I2C, O_RDWR);

    if (fd < 0) {
        printf("Error opening file: \n");
        return -1;
    }

    if (ioctl(fd, I2C_SLAVE, I2C_ADDR) < 0) {
        printf("ioctl error: \n");
        return -1;
    }
    return fd;
};

/*--------------------------------------------------------------------*/
void I2CSetup (int fd) {//Setup mcp23017
    char buffer[2];

    buffer[1]=0x00;//Valeur register

    //Clear ports mcp23017 GPIOB OUTPUT
    for( size_t reg=0x01 ;reg<0x10;reg++){
        buffer[0]=reg;//load register
        write(fd,buffer,2);
        usleep(1000);
    }

    //GPIOA INPUT
    buffer[0]=0x00;//Register IODIRA
    buffer[1]=0xFF;// Value INPUT
    write(fd,buffer,2);

};

/*--------------------------------------------------------------------*/
int iI2CRead (int fd) {//Read  GPIOA
    char buffer[2];
    buffer[0]=0x12;//GPIOA
    write(fd,buffer,1);

    read(fd, &buffer[1], 1);
    return buffer[1];
};

/*--------------------------------------------------------------------*/
void iI2CWrite (int fd, unsigned char data){//write GPB
    char buffer[2];
    buffer[0]=0x13;//GPIOB
    buffer[1]=data;
    write(fd,buffer,2);
};

/*--------------------------------------------------------------------*/
/*--------------------------------------------------------------------*/
int main (void) {
    char buffer[2];

    int fd(-1);

    if ( (fd=I2COpen()) <0){exit (0);}
    I2CSetup (fd);//SetUp mcp23017

    //Read GPIOA
    printf("0x%02X\n",iI2CRead (fd));

    usleep(100000);

    //Write GPIOB
    buffer[1]=0xAA;//Write data
    iI2CWrite (fd, buffer[1]);//write GPB


    return 0;
}