#define STX 2
#define ETX 3
#define EOT 4
#define ACK 0x06
#define ESC 0x1B

#include <sys/types.h>
#include <stdio.h>	/*-- printf(), perror()         --*/
#include <stdlib.h>	/*-- exit()                     --*/
#include <unistd.h>	/*-- STDIN_FILENO, usleep       --*/
#include <termios.h>	/*-- tcgetattr(), tcsetattr()   --*/
#include <signal.h>     /*-- kill()                     --*/

int ch;
struct termios tty, tty_old;
FILE *fd_data, *fd_hs;
char line[5];
pid_t pid;
int status;
useconds_t microseconds;

int main(void) {

printf("%c\n", 'a');
return(0);

  /*-- Create/Open handshake and data channels, and initialize them.     --*/

  fd_hs = fopen("kbHS.txt", "w");        /*-- Open HS channel.           --*/
  if( fd_hs == NULL ) {                       /*-- if fopen() error:     --*/
    perror("kb can't open handshake:");        /*--  report,             --*/ 
    exit(1);                                   /*--  and EXIT(1).        --*/
  }

  fd_data = fopen("kbData.txt", "w");    /*-- Open data channel.         --*/
  if( fd_data == NULL ) {                    /*-- if fopen() error:      --*/
    perror("kb can't open data:");             /*--  report,             --*/ 
    exit(1);                                   /*--  and EXIT(1).        --*/
  }

  fprintf(fd_hs, "%0.2x\n", ACK);       /*--  Write ready   hs sig.      --*/
  fprintf(fd_data, "%0.2x\n", 0x31);    /*--  Write dummy data '1'.      --*/
  fclose( fd_hs ); fclose( fd_data );   /*-- Close HS and data channels. --*/

  /*-- Start child for verilog simulaton. -------------------------*/
  pid = fork(); if(pid == -1) { perror("kb can't fork: "); exit(1); }
  if (pid == 0) {
    status = execlp("vvp", "vvp", "a.out", 0);
    if (status == -1) { perror("kb child can't exec: "); exit(1); }
  }

  /*-- MAIN LOOP: ------------------------------------------------*/
  /*-- Get ascii code per key event, translate ascii to string, --*/
  /*-- write string to data file, write ETX string to hs file.  --*/
  /*-- Exit on ESC.                                             --*/
  while(1) { 


      usleep(1000);

      fd_hs = fopen("kbHS.txt", "r+");       /*-- Open HS channel.           --*/
      if( fd_hs == NULL ) {                      /*-- if fopen() error:      --*/
        perror("kb can't open handshake:");        /*--  report,             --*/ 
        tcsetattr( 0, TCSAFLUSH, &tty_old );       /*--  restore tty,        --*/
        if(status < 0) perror("kb can't reset: "); /*--  if can't, report,   --*/
        kill(pid, SIGTERM); exit(1);               /*--  and EXIT(1).        --*/
      }

      rewind(fd_hs);
      fprintf(fd_hs, "%c\n", ETX);        /*-- Write handshake signal.    --*/
      fclose(fd_hs);                         /*-- Close HS channel.          --*/

      fd_data = fopen("kbData.txt", "r+");   /*-- Open data channel.         --*/
      if( fd_data == NULL ) {                    /*-- if fopen() error:      --*/
        perror("kb can't open handshake:");        /*--  report,             --*/ 
        tcsetattr( 0, TCSAFLUSH, &tty_old );       /*--  restore tty,        --*/
        if(status < 0) perror("kb can't reset: "); /*--  if can't, report,   --*/
        kill(pid, SIGTERM); exit(1);               /*--  and EXIT(1).        --*/
      }
      rewind(fd_data);
      fprintf(fd_data, "%0.2x\n", ch);       /*-- Write char as string.      --*/
      fclose(fd_data);                       /*-- Close data channel.        --*/


  }/*--while(1)--*/

}/*--main--*/

/*-----------------------------------
the idea here is
1. kb.c creates:
    ()  file kbData.txt to send keyboard chars to LC3:kbDevice
    ()  file kbHS1.txt to send STX to LC3:kbdevice.
    ()  NAMED pipe kbHS2.txt to get ACK from LC3:kbdevice.
    ()  NAMED pipe dispData.txt to get char from LC3:dispDevice.
    ()  write( kbHS.txt, ACK )
    ()  write( dispHS.txt, ACK )
    ()  fork()                                () child: exec( a.out )
    LOOP:                                     LOOP-kbDevice:
                                              () readmem( kbHS.txt )
    () if (read(kbHS.txt) == ACK )
         if (read(stdio) == nonNull )
           write( kbData.txt, char )
           write( kbHS.txt, STX )
                                              () if readmem( kbHS.txt ) == STX
                                                     readmem( kbData.txt, char )
                                                     newData <== char
                                                     fwrite( kbHS.txt, ACK )
                                              () go LOOP-kbDevice
                                              LOOP-dispDevice:
                                              () DDR <== char
                                              () if readmem( dispHS.txt ) == ACK
                                                     fwrite( dispData.txt, char)
                                                     fwrite( dispData.txt, STX)
                                                 else goto if (ACK)
                                              goto LOOP-dispDevice
    () if (read(dispHS.txt) == STX)
           char = read(dispData.txt)
           write( dispHS.txt, ACK)
           write(stdout, char)
   goto LOOP-kb.c

*/