Hello,
I'm have connected some device on one of the UART peripherals of the
BeagleBone Black, and now I would like to be able to somehow detect if
there's a "BREAK" sequence present (with some kind of Linux signaling
method).
I have tried with this code:
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#define error_message printf
int set_interface_attribs (int fd, int speed, int parity) {
struct termios tty;
memset (&tty, 0, sizeof tty);
if (tcgetattr (fd, &tty) != 0) {
error_message ("error %d from tcgetattr", errno);
return -1;
}
cfsetospeed (&tty, speed);
cfsetispeed (&tty, speed);
tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8; // 8-bit chars
tty.c_iflag &= IGNBRK; // disable break processing
tty.c_lflag = 0; // no signaling chars, no echo,
// no canonical processing
tty.c_oflag = 0; // no remapping, no delays
tty.c_cc[VMIN] = 0; // read doesn't block
tty.c_cc[VTIME] = 5; // 0.5 seconds read timeout
tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl
tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls,
// enable reading
tty.c_cflag &= ~(PARENB | PARODD); // shut off parity
tty.c_cflag |= parity;
tty.c_cflag &= ~CSTOPB;
tty.c_cflag &= ~CRTSCTS;
//tty.c_iflag = ~BRKINT | ~INPCK;
if (tcsetattr (fd, TCSANOW, &tty) != 0) {
error_message ("error %d from tcsetattr", errno);
return -1;
}
return 0;
}
void breakHandler(int signo) {
printf("\n\nCATCHED!!!\n\n");
}
int main() {
char *portname = "/dev/ttyO5";
int fd = open (portname, O_NOCTTY);
if (fd < 0) {
error_message ("error %d opening %s: %s", errno, portname, strerror (
errno));
return;
}
set_interface_attribs (fd, B19200, 0); // set speed to 192,000 bps, 8n1
(no parity)
char buf [100];
if (signal(SIGINT, breakHandler) == SIG_ERR) {
printf("\n\nCan't catch SIGINT!\n\n");
}
fcntl(fd, F_SETOWN, getpid());
struct sigaction saio; /* definition of signal action */
saio.sa_handler = breakHandler;
saio.sa_flags = 0;
saio.sa_restorer = NULL;
sigaction(SIGINT, &saio, NULL);
while(1) {
int n = read (fd, buf, sizeof buf); // read up to 100 characters if
ready to read
usleep ((95 + 25) * 100);
printf("\n I read:\n");
int i;
for(i = 0; i < n; i++) {
printf("%#08x ", buf[i]);
}
printf("\nError: %s\n", strerror(errno));
}
return 0;
}
But it seems that it's not working, the signal is only triggered when I
press CTRL+C on my keyboard.
What should be the problem?
Thanks.
--
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