Writing .txt file in SD Card - DE2

Hello! I successfully create a file in my SD card! I only having problems to write in the file! I am doing some tests I post my results when I get something.

Here is my C program:

# include <stdio.h>

# include <altera_up_sd_card_avalon_interface.h>

# include <altera_avalon_pio_regs.h>

int main(void){

alt_up_sd_card_dev *device_reference = NULL;

int connected = 0;

short int arquivo = 0;

short int att = 0;

char data = 0;

printf("Insira o SD Card \n");

device_reference = alt_up_sd_card_open_dev("/dev/Altera_UP_SD_Card");

if (device_reference != NULL) {

while(1){

if((connected ==0) && (alt_up_sd_card_is_Present())){

printf("SD Card Connected. \n");

IOWR_ALTERA_AVALON_PIO_DATA(LEDR_BASE, 0xFFFF);

if(alt_up_sd_card_is_FAT16()){

printf("FAT16 file system detected!!! \n");

/* Start to create a file */

arquivo = alt_up_sd_card_fopen ("file.txt", true);

printf ("fopen returns: %d\n", arquivo);

alt_up_sd_card_write(arquivo, data);

att = alt_up_sd_card_get_attributes(arquivo);

printf ("get_attrubutes return: %d\n", att);

/*alt_up_sd_card_fclose(arquivo);*/

/* End */

} else{

printf("Unknown file system. \n");

}

connected = 1;

} else if ((connected == 1) && (alt_up_sd_card_is_Present() == false)){

printf("SD disconected. \n");

IOWR_ALTERA_AVALON_PIO_DATA(LEDR_BASE, 0);

connected = 0;

}

}

}

return 0;

}