/*
PCF8574_addr_byteout--read_to_ramdisk_slug.c
--------------------------------------------
Send address and byte to switch/read lines on 8 line port of i2c bus PCF8574
----------------------------------------------------------------------------
Save result to ramdisk file
---------------------------

1) send the i2c address
2) send byte as decimal to set the 8 port lines on or off
3) read the line states and save in /var/www/ramdisk/PCF8574_port_byte.dat

example-
use port line 0 as output to control a relay
detect the states of the lines 1 to 7
send <i2c address-byte> <255 for line 0 HI>or<254 for line 0 LO>
the read will report the state of all the lines

usage :- type with spaces but without the < >
<PCF8574_addr_byteout--read_to_ramdisk_slug> <decimal address> <decimal byte out 0-255>

*/
#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 != 3) { /* error if we are not getting just 2 inputs 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]);
/* the byte to send out to the PC8574 is the second number*/
data[0] = atoi(argv[2]);

i2c = open("/dev/i2c-0",O_RDWR); /* open the device dev/i2c-0 */

rc=ioctl(i2c,I2C_SLAVE,address); /* set the i2c chip address */

write(i2c,data,1) ; /* send the byte */

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

byte = data[0];

// printf("%d", byte); ( not used in this program)
/* BYTE value is 0-256 - print no return character - just the byte)*/

//save port byte to ramdisk
FILE *f;
f = fopen("/var/www/ramdisk/PCF8574_port_byte.dat","w");
fprintf(f, "%d", byte);
fclose(f);

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

/*
PCF8591_address_channel_Vout-ramdisk_slug.c
------------------------------
read the voltage on one A/D lines (0-3) and set the output voltage on the D/A pin
---------------------------------------------------------------------------------

1) send the i2c address
2) choose channel 0-3
3) send byte for D/A out
4) read channel volts as 5 x (byte_received)/255)
usage :- type with spaces but without the < >
<PCF8591_address_readvolts> <address as decimal> <channel 0-3> <D/A value as decimal 0-255>
(even if the D/A pin is unused type in any value 0-255)
4) save decimal byte to /var/www/ramdisk/AtoD.dat
*/

#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 channel; /* line number 0-3 */
int V_out; /* value for the D/A out line */
unsigned char buf[1]; /* use to feed the i2c driver */
unsigned long address; /* i2c bus address */
int byte_in_0; /* the 8 bit byte that represents the voltage on the AD_line */
int AD_input; /* volts byte on chosen channel */

int rc;

int main(int argc, char** argv)
{
if (argc != 4) /* report error if we are not getting just 3 inputs after the program name */
{
printf("Error. usage: %s i2c_chip_address channel_to_read D/A_Vout(0-255)\n", argv[0]);
}

address = atoi(argv[1]); /* decimal address is the first number after the program name */
channel = atoi(argv[2]); /* choose A to D line to read 0-3 */
V_out = atoi(argv[3]); /* volts out as decimal 0-255 */

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

channel = channel + 64; /* control register - enable the D/A output */
buf[0] = channel; /* A/D input line number is the first data byte sent */
buf[1] = V_out; /* D/A out value is the second data byte sent */
write(i2c,buf,2); /* we send 2 bytes <control register> <D/A value> */
read(i2c,buf,1); /* buf(0) contains the byte of data in the chip cache */
usleep (1000); /* do it again */
read(i2c,buf,1); /* buf(0) now contains the byte of data from the most recent analogue input*/
AD_input = buf[0];

//printf("%d", AD_input);
/*AD_line_x goes 0 to 255 as voltage input goes from 0 to supply voltage*/

//save AtoD byte to ramdisk
FILE *f;
f = fopen("/var/www/ramdisk/AtoD.dat","w");
fprintf(f, "%d", buf[0]);
fclose(f);

i2c = close(i2c);
return(0);
}
/* Sunspot 091108 - (Google/copy/paste c code - thanks to sources) */