Serial port read() blocking
Hi everyone
I am having an infuriating time trying to get my c code to read from the serial port under Linux. When ever I execute the code the program blocks on the read() function even after I have inputted 5 characters (as defined in c_cc[VMIN]) - it should fall through and end the application however it just sits on the read() function.
At the serial end I get a block of 5 characters printed to the screen after the obligatory 5 have been entered even though I believe I have told it not to echo the input characters...
Ahhhhrgg! If can anyone could help me out I would be incredibly great full as this is driving me nuts!
Many thanks :)
Code:
#include <fcntl.h>
#include <termios.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#define BAUDRATE B9600
#define MODEMDEVICE "/dev/ttyS0"
#define FALSE 0
#define TRUE 1
int main() {
printf("Start\n");
int fd, res;
struct termios oldtio,newtio;
char buf[255];
fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY );
if (fd <0) {
printf("Failed to open %s", MODEMDEVICE);
} // if
else {
printf("Port Opened\n");
tcgetattr(fd,&oldtio); /* save current port settings */
bzero(&newtio, sizeof(newtio));
newtio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD;
newtio.c_iflag = IGNPAR;
newtio.c_oflag = 0;
// set input mode (non-canonical, no echo,...) */
newtio.c_lflag = 0;
newtio.c_cc[VTIME] = 0; /* inter-character timer unused */
newtio.c_cc[VMIN] = 5; /* blocking read until 5 chars received */
tcflush(fd, TCIFLUSH);
tcsetattr(fd,TCSANOW,&newtio);
res = read(fd,buf,255); /* returns after 5 chars have been input */
buf[res]=0; /* so we can printf... */
printf("Input: %s\n", buf);
tcsetattr(fd,TCSANOW,&oldtio);
} // else */
printf("Done\n");
return 0;
} // main
