serial port configuration

[windell]

Hi, I'm currently writing a program that only reads characters from the serial port. The device connected to the port only puts out data. I would then like to convert the byte values into hex.

To get the data from the serial port I used the following tutorial:
Serial Programming Guide for POSIX Operating Systems - Michael R Sweet
however, I don't think I am understanding all of it because I am sending ASCII characters from a windows machine and my program isn't displaying the data to the screen. I am using a crossover able between the two computers.

My hunch is that I do not have the port configured right. I barely understood that part of the tutorial.

If any of you could help me figure out what is wrong and help me find a way to simplify the port configuration, I would be very grateful!

Thank you very much for your time,
windell

Here is what my code looks like...I took out the none essential parts.

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

#define BYTE_COUNT 38

int main()
{
char port_name[] = "/dev/ttyUSB0";	//set port name here.

/*variable declarations*/
int serial_port;
struct termios options;
char input[50];
char old_string[50];
int i,print_flag;

/*initialize arrays*/
for(i=0;i<50;i++){
	input[i]='n';
	old_string[i]='n';
}

//-------------open port---------------------------------
serial_port = open(port_name, O_RDWR | O_NOCTTY | O_NDELAY);
if (serial_port < 0){
	printf("unable to open %s\n",port_name);
	exit(0);
}
else
{
	printf("Connected to %s\n",port_name);
//	fcntl(serial_port,F_SETFL,0);
}
//----------------------------------------------------------

/*configure port (don't know what this stuff does)*******************/
//get current options for the port.
tcgetattr(serial_port, &options);

//set the receive baud rate to 115200 baud
cfsetispeed(&options, B115200);

//enable the receiver and set local mode...
options.c_cflag |= (CLOCAL|CREAD);

//set the new options for the port.
tcsetattr(serial_port, TCSANOW, &options);

//8N1.
options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;

//disable flow control.
options.c_cflag &= ~(IXON | IXOFF | IXANY);

//choose raw input.
options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
/**********************************************/

while (1)
{

read(serial_port,input,BYTE_COUNT);	//store incoming data.
input[BYTE_COUNT]='\0';			//terminate string.


printf("%s\n",input);			//print the input to screen.

/*nonessential code here.*/
}
//-----------------------------------------------------------


/*dont know what these do!*/
tcsetattr(serial_port, TCSANOW, &options);  
tcflush(serial_port, TCOFLUSH);
tcflush(serial_port, TCIFLUSH);

//close the serial port.
close(serial_port);
serial_port = -1;

return 0;
}

[csdude]

>tcgetattr(serial_port, &options);
puts the current ports settings in a struct

>cfsetispeed(&options, B115200);
linespeed (you should set out speed too)


>//set the new options for the port.
>tcsetattr(serial_port, TCSANOW, &options);
You probably want to do this after the following lines.

>//8N1.
>options.c_cflag &= ~PARENB;
>options.c_cflag &= ~CSTOPB;
>options.c_cflag &= ~CSIZE;
>options.c_cflag |= CS8;

>//disable flow control.
>options.c_cflag &= ~(IXON | IXOFF | IXANY);

>//choose raw input.
>options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);


this is where you do the tcsetattr (because else it doesn't make sense to
change the struct members in options


>/**********************************************/

>while (1)
>{



.... snip ....

>/*dont know what these do!*/
>tcsetattr(serial_port, TCSANOW, &options);

set option to be effective immediately

>tcflush(serial_port, TCOFLUSH);
>tcflush(serial_port, TCIFLUSH);
flush the serial IO buffers

those 5 lines go before the 'tcsetattr' too

>//close the serial port.
>close(serial_port);
>serial_port = -1;

>return 0;