This program checks for the presence of an XBee module in the TS-7553 socket.

Note that the XBee is connected to a serial port in the FPGA. The serial port needs to be activated by xuartctl before it can be used.

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/select.h>
#include <fcntl.h>
#include <termios.h>
#include <stdio.h>
#include <strings.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>

int main( int argc, char **argv ){
  int fd, res, n;
  struct termios oldtio, newtio;
  char buf[255] = {0}, *c;
  char comport[255];
  const char cmd[] = "xuartctl --server --port 3 --speed 9600 2>&1";
  FILE *fp;
  fd_set input;
  struct timeval timeout;  

  // setup com port using xuartctl
  fp = popen( cmd, "r" );
  while( fgets( buf, sizeof buf, fp )){
    //printf( "Received: %s-\n", buf );
    c = strchr( buf, '=' );
    strcpy( comport, c+1 );
    *(comport+strlen(comport)-1) = 0;  // remoew new line
    printf( "Using port %s\n", comport );
  }
  pclose( fp );

  // open port
  fd = open( comport, O_RDWR | O_NOCTTY );
  if( fd < 0 ){
    // nope, bail
    perror( comport );
    return( -1 );
  }  

  // ----- Configure port -----
  // save current port settings
  tcgetattr( fd, &oldtio );
  // define timeout
  timeout.tv_sec = 3;
  timeout.tv_usec = 0;
  // define new terminal structure
  bzero( &newtio, sizeof( newtio ));
  newtio.c_cflag = CRTSCTS | CS8 | CLOCAL | CREAD;
  newtio.c_iflag = IGNPAR;
  cfsetispeed( &newtio, B9600 );
  cfsetospeed( &newtio, B9600 );
  newtio.c_oflag = 0;
  
  newtio.c_lflag = 0;       // set input mode (non-canonical, no echo,...)
  newtio.c_cc[VTIME] = 0;   // inter-character timer unused
  newtio.c_cc[VMIN] = 2;    // blocking read until 2 chars received
  
  tcflush( fd, TCIFLUSH );
  tcsetattr( fd, TCSANOW, &newtio );
  
  // Sending +++ within 1 second sets the XBee into command mode
  printf( " Sending +++\n" );
  write( fd, "+++", 3 );

  // initialize "input" to contain fd:
  FD_ZERO( &input );
  FD_SET( fd, &input );  
  n = select( fd+1, &input, NULL, NULL, &timeout );
  
  if( n < 0 )
    printf( "select() failed\n" );
  else if( n == 0 )
    printf( "TIMEOUT, no XBee\n" );
  else{
    res = read( fd, buf, 250 );
    buf[res] = 0;
    //printf( "Received: %s\n", buf );
    if( 0 == strncmp( buf, "OK", 2 )){
      printf( "XBee Detected\n" );
    }else{
      printf( "Something else responded!\n" );
    }
  }
  tcsetattr( fd, TCSANOW, &oldtio );
  return( 0 );
}

To make the program, name this file “hello.c: and simply type “make hello” at the command line.