/* 
    PIC_i2c_one_value.c
    Read value of A to D input
    ------------------------------
 
      1) send the i2c address
      2) send StartPoint
      3) send 2 data bytes for buffer (address 0/1)
      4) read 2 bytes from PIC and print
  usage :-  type with spaces but without the < >
<PIC_i2c_one_value.c>  <i2c address as decimal(80)> <buffer address> <x>  <display command>
use x = 0, 2, 4
to read A to D lines 0,1,2
*/

#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; 
  int BufferAddress;       /* which buffer[] to hold start of data */
  int DataForBuffer[8];       /* values for the PIC buffer[BufferAddress] */
  int PicData[8];             /* byte sent by PIC*/
  unsigned char buf[8];    /* 3 bytes - use to feed the i2c driver */
  unsigned long address;   /* i2c bus address */

  int rc;

int main(int argc, char** argv)
{
 if (argc != 5)   /* report error if we are not getting just 4 inputs after the program name */
 {
  printf("Error. usage: %s i2c_chip_address  BufferAddress  data_for_buffer[address]-(6 data numbers)\n", argv[0]);           
 }

  address = atoi(argv[1]); /* i2c decimal address is the first number after the program name */
  BufferAddress = atoi(argv[2]); /* the array number for buffer */
  DataForBuffer[1] = atoi(argv[3]); /* data for  buffer[BufferAddress]*/
  DataForBuffer[2] = atoi(argv[4]); /* data for  buffer[BufferAddress+1]*/

  //------------------------------------------------------------------------send all data then read PicData1
 i2c = open("/dev/i2c-0",O_RDWR); /* open the device dev/i2c-0 */
 rc=ioctl(i2c,I2C_SLAVE,address); /* set the i2c chip address */

  buf[0] = BufferAddress;   /* address in buffer to start recording received data */
  buf[1] = DataForBuffer[1];     /* first data byte to be sent - used for moving up array of return data*/
  buf[2] = DataForBuffer[2];     /* display command byte*/

  
  write(i2c,buf,3);   /* we send 7 bytes <BufferAddress> <Datas For Buffer1/2> */
  
   /* the next command forces the PIC to respond - it makes "(state == 0x80)" in the PIC */
  read(i2c,buf,1);    /* buf(0) now contains 1 data byte from PIC */
  PicData[1] = buf[0];
  //printf("%d \n", PicData[1]);
  i2c = close(i2c);
    //---------------------------------------------------------------------read next data - PicData2
   i2c = open("/dev/i2c-0",O_RDWR); /* open the device dev/i2c-0 */
 rc=ioctl(i2c,I2C_SLAVE,address); /* set the i2c chip address */

  buf[0] = BufferAddress;   /* address in buffer to start recording received data */
  buf[1] = DataForBuffer[1] + 1;     /* first data byte to be sent */
  write(i2c,buf,2);   /* we send 3 bytes <BufferAddress> <DataForBuffer1> <DataForBuffer2>*/
  
   /* the next command forces the PIC to respond - it makes "(state == 0x80)" in the PIC */
  read(i2c,buf,1);    /* buf(0) now contains 1 data byte from PIC */
  PicData[2] = buf[0];
  //printf("%d \n", PicData[2]);
  i2c = close(i2c);
  
 printf("%d \n", PicData[1] + 256*PicData[2]);
    
}