// Rapsberry Pi: I2C in C - Versione 0.64 - Luglio 2013
// Copyright (c) 2013, Vincenzo Villa (https://www.vincenzov.net)
// Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.
// Creative Commons | Attribution-Share Alike 3.0 Unported
// https://www.vincenzov.net/tutorial/RaspberryPi/i2c_c.htm

// Compile:  gcc MCP23017-2.c -std=c99 -o MCP23017-2
// Run as user with R&W right on /dev/i2c-* (NOT ROOT!)
// vv@vvrpi ~ $ ./MCP23017-2 X
// 0 <= X <= 255 
// Using MCP23017 - I2C 

#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/i2c-dev.h>
#include <stdlib.h>

#define I2C_ADDR 0x20				// Device adress
#define DATA_TO_READ 22

#define MCP23017_IODIRA 0                       // IODIRA (see data sheet)
#define MCP23017_IODIRB 1			// IODIRB (see data sheet)
#define MCP23017_GPPUA 0x0C                     // GPPUA (see data sheet)
#define MCP23017_GPIOA 0x12                     // GPIOA (see data sheet)
#define MCP23017_GPIOB 0x13                     // GPIOB (see data sheet)
#define MCP23017_IOCON 0x05                     // IOCON (see data sheet)

static const char *device = "/dev/i2c-1";	// I2C bus

static void exit_on_error (const char *s)	// Exit and print error code
{ 	perror(s);
  	abort();
} 

int main(int argc, char *argv[])
{
	int fd;
	
	int32_t SMBUS_word;
	uint8_t datas[DATA_TO_READ];
	uint8_t data; 
	
        printf("Rapsberry Pi: I2C in C - Versione 0.64 - Luglio 2013\n");
        printf("Copyright (c) 2013, Vincenzo Villa (https://www.vincenzov.net)\n");
        printf("Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.\n");
        printf("Creative Commons | Attribution-Share Alike 3.0 Unported\n");
        printf("https://www.vincenzov.net/tutorial/elettronica-di-base/RaspberryPi/i2c-c.htm\n\n");                                       

        if (argc != 2) 
        { 
          printf ( "Usage: \n rpi ~ $ ./MCP23017-2 X\n X is an integer number from 0 to 255\n\n");
          exit(-1);        
         }

       	// Open I2C device
       	if ((fd = open(device, O_RDWR)) < 0) exit_on_error ("Can't open I2C device");

	// Set I2C slave address
	if (ioctl(fd, I2C_SLAVE,I2C_ADDR) < 0) exit_on_error ("Can't talk to slave");
        
        // Configure PortB as output      
        if ( (SMBUS_word = i2c_smbus_write_byte_data(fd , MCP23017_IODIRB, 0x00 )) < 0) exit_on_error ("Failed to write to the i2c bus [1]");
         
        // Put data to PortB      
        data = atoi(argv[1]);
        if ( (SMBUS_word = i2c_smbus_write_byte_data (fd , MCP23017_GPIOB, data )) < 0) exit_on_error ("Failed to write to the i2c bus [2]");                      
        printf("Write 0x%X to PortB\n\n", data );

        // Configure PortA as input          
        if ( (SMBUS_word = i2c_smbus_write_byte_data (fd , MCP23017_IODIRA, 0xFF )) < 0) exit_on_error ("Failed to write to the i2c bus [3]");
                                
        // Enable pull-up on PortA                                  
        if ( (SMBUS_word = i2c_smbus_write_byte_data (fd , MCP23017_GPPUA, 0xFF )) < 0) exit_on_error ("Failed to write to the i2c bus [4]");
        
        // Read from PortA                                                
        if ( (SMBUS_word = i2c_smbus_read_byte_data (fd , MCP23017_GPIOA )) < 0) exit_on_error ("Failed to read from the i2c bus [1]");
        printf("Data read from PortA: 0x%X\n\n", SMBUS_word);      

        // Read a block of bytes
        if ( (SMBUS_word = i2c_smbus_read_i2c_block_data (fd , 0, DATA_TO_READ, datas )) < 0) exit_on_error ("Failed to read from the i2c bus [2]");
        printf("Reading %d byte: ", SMBUS_word);  
        for (int i = 0; i < DATA_TO_READ; i++)  printf("%.2X ",  datas[i]);
        printf("\n\n");

        close(fd);

	return (0);
}