I am not sure how much this will help, but...
I know when I started playing around with using an XBee connected to an XBee shield using this IO port, that I had to play around with the code for awhile to get it to work right for me. The first set of code I got working is my Robot (Arm or Hex or) controlled by Edison talking to Arbotix Commander Remote control.
Note: My c/c++ code creates a thread to actually process the IO. I also open it as device /dev/ttyXBEE where I create an alias to this port. I am also using the port at the speed 38400... This code earlier worked on BBBk, ODroid U2/U3, RPI... But I modified it to be closer to the init code that the Arduino IDE does for the Serial1 object.
The initial Init code looks like:
bool Commander::begin(char *pszDevice, speed_t baud)
{ int err; // Create our lock to make sure we can do stuff safely if (pthread_mutex_init(&lock, NULL) != 0) return false; _fCancel = false; // Flag to let our thread(s) know to abort.
#ifdef CMDR_USE_XBEE _pszDevice = pszDevice; _baud = baud; // Lets do our init of the xbee here. // We will do all of the stuff to intialize the serial port plus we will spawn off our thread. struct termios tc, tcNew; if ((fdXBee = open(_pszDevice, O_RDWR | O_NONBLOCK)) == -1) { printf("Open Failed\n"); return 0; } if (tcgetattr(fdXBee, &tc)) { perror("tcgetattr()"); return 0; } // build new version bzero(&tcNew, sizeof(tcNew)); //newtios.c_cflag |= _dwBaudRate | CRTSCTS | CS8 | CLOCAL | CREAD; tcNew.c_cflag = tc.c_cflag; tcNew.c_cflag &= ~CBAUD; tcNew.c_cflag |= _baud; tcNew.c_iflag = IGNPAR; tcNew.c_oflag = 0; /* set input mode (non-canonical, no echo,...) */ tcNew.c_lflag = 0; tcNew.c_cc[VTIME] = 0; /* inter-character timer unused */ tcNew.c_cc[VMIN] = 1; /* blocking read until 1 chars received */ tcflush(fdXBee, TCIFLUSH); tcsetattr(fdXBee, TCSANOW, &tcNew); // Now we need to create our thread for doing the reading from the Xbee pthread_barrier_init(&_barrier, 0, 2); err = pthread_create(&tidXBee, NULL, &XBeeThreadProc, this); if (err != 0) return false; // sync startup pthread_barrier_wait(&_barrier);
#endif
#ifdef CMDR_USE_SOCKET
// Now we need to create our thread for doing the reading from the Xbee err = pthread_create(&tidSocket, NULL, &SocketThreadProc, this); if (err != 0) return false;
#endif
return true;
}
If looking at the code would help, my code is up on github (kurte/raspberry_Pi) project in the library/commanderEx.cpp file. Again it is modified to be similar to what the Edison Arduino system does for Serial1 in the function void TTYUARTClass::begin( const uint32_t dwBaudRate ) in the file TTYUART.cpp.
good luck
