/* Simple send and receive C example for communicating with the
*  Arduino echo program using UART4. 
*
* Written by Derek Molloy for the book "Exploring BeagleBone: Tools and 
* Techniques for Building with Embedded Linux" by John Wiley & Sons, 2014
* ISBN 9781118935125. Please see the file README.md in the repository root 
* directory for copyright and GNU GPLv3 license information.            */

#include<stdio.h>
#include<fcntl.h>
#include<unistd.h>
#include<termios.h>
#include<string.h>

int main(int argc, char *argv[]){
   int file, count;
   if(argc!=2){
       printf("Invalid number of arguments, exiting!\n");
       return -2;
   }
   if ((file = open("/dev/ttyO4", O_RDWR | O_NOCTTY | O_NDELAY))<0){
      perror("UART: Failed to open the file.\n");
      return -1;
   }
   struct termios options;
   tcgetattr(file, &options);
   options.c_cflag = B57600 | CS8 | CREAD | CLOCAL;
   options.c_iflag = IGNPAR | ICRNL;
   tcflush(file, TCIFLUSH);
   tcsetattr(file, TCSANOW, &options);

   // send the string plus the null character
   if ((count = write(file, argv[1], strlen(argv[1])+1))<0){
      perror("Failed to write to the output\n");
      return -1;
   }
   usleep(100000);
   unsigned char receive[100];
   if ((count = read(file, (void*)receive, 100))<0){
      perror("Failed to read from the input\n");
      return -1;
   }
   if (count==0) printf("There was no data available to read!\n");
   else {
      receive[count]=0;  //There is no null character sent by the Arduino
      printf("The following was read in [%d]: %s\n",count,receive);
   }
   close(file);
   return 0;
}