How to use C++ for transmitting data using xbee? - c++

Question

For a project i need to establish 2 way xbee communication. But I have a problem sending data from my pc. I use cpp with termios to transmitt a char array but on the xbee tx pin I do only get a signal (I observe this on an oscilloscope) when one of the chars is 0x0A.
The XBee module is on a 30011662-02 board, which is connected to my pc via usb.
I thought maybe this is some kind of starting parameter needed by the xbee board to transmit but couldnt find any information on this.
ctx->debug = debug;
//open USB port for read/write and check success
ctx->fd = open(devFileName, O_RDWR | O_NOCTTY); //opens the usb port for reading
if (ctx->fd < 0) {
cerr << "Could not open the USB Port. Try adding User to group dialout!" << endl;
return 0;
}
//is the opened port a terminal?
if(!isatty(ctx->fd)) {
close(ctx->fd);
errno = ENOTTY;
return 0;
}
//setup termios
tcgetattr(ctx->fd, &(ctx->oldtio));
cfmakeraw(&newtio);
cfsetispeed(&newtio, baudrate);
cfsetospeed(&newtio, baudrate);
tcsetattr(ctx->fd, TCSANOW, &newtio); //connects fd to newtio
tcflush(ctx->fd, TCIOFLUSH); //discards data not transmitted or received
lseek(ctx->fd, 0, SEEK_END);
ctx->bufIO = fdopen(ctx->fd, "r+");
bool connection_status=0;
unsigned char frame_id=0x00;
unsigned char checksum=0xff;
int j=0;
while(!connection_status){
checksum=0xFF;
unsigned char buffer[] = {
0x7E, //start delimiter
0x00,0x07,//length of the data packet
0x01,//API identifier (refer to XBee module manual for further details)
frame_id++, //frame id
0x00,0x0B,//destination address
0x00,//options
0x02,0x03,//data: 0,receiver address,mode
0x00}; //checksumm
for(unsigned int i=0;i<sizeof(buffer);i++){
checksum-=buffer[i];
}
cout << buffer << endl;
j++;
buffer[10]=checksum;
fwrite(buffer,sizeof(char),sizeof(buffer),ctx->bufIO);
usleep(2000000);
}
I do expect to see data on the xbee tx pin in every itteration of the while loop but so far it only works when frame_id is 0x0A or i manually enter 0x0A in the array buffer. But still it does not seem to be sending the correct data. Maybe you have some hints for me.

Answer 1

You're probably missing a setting (maybe O_NDELAY?) for the serial port (tty) and it's in line mode. You might want to look at this serial driver used in an Open Source XBee Host Library written in ANSI C (instead of C++). You might even be able to build your application on top of that library. At the very least, you could compile the samples and see if they work with your module as a way to verify your wiring and XBee configuration.