// Rapsberry Pi: RS232 in C - Versione 0.8 - Luglio 2014
// Copyright (c) 2014, 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/serial.htm

// Compile:  gcc serial.c -std=gnu99 -o serial
// vv@vvrpi ~ $ ./serial <data_to_send>

#include <termios.h>
#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 <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <errno.h>

#define PORT "/dev/ttyAMA0"   // Device name
#define SPEED B115200         // I/O speed - B9600 and so on 
#define DATA_BUFFER_SIZE 100  // RX buffer data size  
int fd;                       // Serial handler

int open_and_configure_interface (void)
{struct termios tty;          // Device descriptor
  
 fd = open (PORT, O_RDWR);    // Open device
      
 if (fd < 0)
          {printf ("Error %d opening %s: %s\n", errno, PORT, strerror (errno));
           return (-1);
          }
                                    
 memset (&tty, 0, sizeof tty);
 if (tcgetattr (fd, &tty) != 0)
        {printf("ERROR! %s\n", strerror(errno));
         return (-1);
        }

 cfsetospeed (&tty, SPEED);                      // Set output speed 
 cfsetispeed (&tty, SPEED);                      // Set input speed 
 tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;     // 8-bit chars
 tty.c_iflag &= ~IGNBRK;                         // Disable break processing
 tty.c_lflag = 0;                                // No signaling chars, no echo, no canonical processing
 tty.c_oflag = 0;                                // No remapping, no delays
 tty.c_cc[VMIN]  = 0;                            // Read doesn't block
 tty.c_cc[VTIME] = 5;                            // 0.5 seconds read timeout
 tty.c_iflag &= ~(IXON | IXOFF | IXANY);         // No xon/xoff ctrl
 tty.c_cflag |= (CLOCAL | CREAD);                // Ignore modem controls, enable reading
 tty.c_cflag &= ~(PARENB | PARODD);              // No parity
// tty.c_cflag |= 0;
 tty.c_cflag &= ~CSTOPB;                         // Set bit stop
 tty.c_cflag &= ~CRTSCTS;                        // No gandshake

 if (tcsetattr (fd, TCSANOW, &tty) != 0)
        {printf("ERROR! %s\n", strerror(errno));
         return (-2);
        }
        
 return (0);
}


int main(int argc, char *argv[])
{ char buffer [DATA_BUFFER_SIZE];                 // Data buffer (Rx)

  printf("Rapsberry Pi: serial port in C - Versione 0.8 - Luglio 2014\n");
  printf("Copyright (c) 2014, 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/RaspberryPi/serial.htm\n\n");

  if (argc < 2)
   { printf("Usage: ./serial <data_to_send>\n\n");
     exit (-1);
   }
                                                                                                                                          
  printf ("Opening %s\n", PORT);
  
  open_and_configure_interface();
    
  sleep(1);                                       // Kernel bug workaround - see text
  
  printf("User data [%d bytes]: %s\n", strlen(argv[1]), argv[1]);
  write (fd, argv[1], strlen(argv[1]) );          // send data

  sleep(1);                                       // Sleep enough to get reply

  memset (buffer, 0, sizeof(buffer) );            // Clear data buffer

  int n = read (fd, buffer, sizeof(buffer));      // Read up to 100 characters

  if (n < 0) printf("ERROR! %s\n", strerror(errno));
          
  printf("Data from device [%d bytes]: %s\n\n", n, buffer);
  
  close (fd);
  
  return (0);
}