/* 
    PCF8574_addr_read_Biff.c
    -------------------
	read the data on the 8 line port of an i2c bus PCF8574
	------------------------------------------------------

	1) set the i2c address of the PCF8574
	2) send data 255 to turn off all 8 lines - make them inputs
	3) read the data on the 8 port lines as a byte
  usage :- type (without the < >)
  <PCF8574_addr_read_Biff> <space> <i2c_bus_address_of_PCF8574_as_decimal>
*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/i2c-dev.h>
#define I2C_SLAVE	0x0703	/* Change slave address	*/

  int i2c;
  char filename[20];
  unsigned long address;
  int rc;
  unsigned char data[1];
  int byte;    /* the 8 bit byte that represents the data present on the 8 wire port */

int main(int argc, char ** argv) 
{
  if (argc != 2) {  /* error if we are not getting just 1 input after the program name */
    fprintf(stderr, "usage: %s <address> <databyte>\n",argv[0]);
    exit(1);
}  

  /* address is the first number after the program name */
  address = atoi(argv[1]);

 i2c = open("/dev/i2c-0",O_RDWR); /* open the device dev/i2c-0 */
 rc=ioctl(i2c,I2C_SLAVE,address); /* set the i2c chip address */

  data[0] = 255; 
  write(i2c,data,1); /* we send 255 to make all lines go off, ready for input data */

  read(i2c,data,1); /* now data(0) contains the byte of data on the 8 port lines*/

  byte = data[0];

  printf("BYTE = %d \n", byte); 
	/* BYTE value is 0-256)*/
 

  i2c = close(i2c);
  return(0);
}