Problem with reading nonblocking /dev/com in 1.7.10 and up
Abdul Muis
muis@ui.ac.id
Tue Apr 10 18:17:00 GMT 2012
I have notice that I could not read serial device (/dev/com4 or
/dev/ttyS3) with non blocking mode since 1.7.10 and up. I used to read
serial data while doing openGL visualization. In which, the openGL
display was not changed due to blocking mode reading.
The command is
fcntl(fd, F_SETFL, FNDELAY); // set reading as non blocking mode, should
return '0' if no data comming
n=read(fd, &test, 10); // starting from 1.7.10 always return -1 although
there is incoming data
There is no problem with blocking mode, the program can read incoming data
fcntl(fd, F_SETFL, 0); // blocking mode
n=read(fd, &test, 10); // the program will stop here until incoming data
arrived
Before reporting this bug, I have tested in Windows 7 32bit, Windows 7
64bit.
luckily I have several cygwin version in different folder.
I have tested the program in version 1.7.9, 1.7.10, 1.7.11, and current
version 1.7.13 at both 32bit and 64bit Windows7.
The program can read in non blocking mode only in 1.7.9
In addition, although I compiled the program in 1.7.10 and put
cygwin1.dll (ver. 1.7.9) in the same folder, the program could read in
non blocking mode too. So, I suspect the bug is in cygwin1.dll in
version 1.7.10 and up.
Unfortunately, if I compiled the program in 1.7.11 and 1.7.13 then used
cygwin1.dll (ver. 1.7.9) the program stuck.
I notice in version 1.7.10, there are additional API_MINOR changed
(/usr/include/cygwin/version.h)
238: Export pthread_spin_destroy, pthread_spin_init, pthread_spin_lock,
pthread_spin_trylock, pthread_spin_unlock.
239: Export pthread_setschedprio.
240: Export ppoll.
241: Export pthread_attr_getstack, pthread_attr_getstackaddr,
pthread_getattr_np.
242: Export psiginfo, psignal, sys_siglist.
243: Export sysinfo.
244: Export clock_settime.
245: Export pthread_attr_getguardsize, pthread_attr_setguardsize,
pthread_attr_setstack, pthread_attr_setstackaddr.
246: Add CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID.
Export clock_getcpuclockid, pthread_getcpuclockid.
247: Export error, error_at_line, error_message_count, error_one_per_line,
error_print_progname.
248: Export __fpurge.
249: Export pthread_condattr_getclock, pthread_condattr_setclock.
250: Export clock_nanosleep.
251: RTLD_NODELETE, RTLD_NOLOAD, RTLD_DEEPBIND added.
252: CW_CVT_ENV_TO_WINENV added.
253: Export TIOCSCTTY, tcgetsid.
254: Export getgrouplist.
255: Export ptsname_r.
256: Add CW_ALLOC_DRIVE_MAP, CW_MAP_DRIVE_MAP, CW_FREE_DRIVE_MAP.
257: Export getpt.
258: Export get_current_dir_name.
259: Export pthread_sigqueue.
I don't know what kind of changed that made non blocking read failed. I
attached the program for testing.
I really hope next version will make it possible again.
Thanks in advanced for all efforts.
Kind regards,
Abdul Muis
-------------- next part --------------
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h> /* File control definitions */
#include <errno.h> /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */
#include <sys/time.h>
#include <io.h>
int fd, fser1, fser2;
int baud, parity;
int open_port(void) {
int fd; // File Descriptor for serial port
char s[60]="/dev/com4";
baud=19200;
parity=0;
printf("Checking communication port : %s\n",s);
fd = open(s, O_RDWR | O_NOCTTY | O_NDELAY);
if(fd == -1) {
perror("-- Unable to open /dev/com --");
exit(1);
} else {
fcntl(fd, F_SETFL, 0);
printf("...Done\n");
}
return(fd);
}
void init_port(int fd) {
struct termios configs;
tcgetattr(fd, &configs);
switch(baud) {
case 9600: baud=B9600;break;
case 19200: baud=B19200;break;
case 38400: baud=B38400;break;
default: baud=B19200;
}
cfsetispeed(&configs, baud);
cfsetospeed(&configs, baud);
// Setting Control Mode
switch (parity) {
case 1: // even parity
configs.c_cflag |= PARENB; // Parity enable
configs.c_cflag &= ~PARODD; // Even Parity
break;
case 2: // odd parity
configs.c_cflag |= PARENB; // Parity enable
configs.c_cflag |= PARODD; // Even Parity
break;
default : // no parity
//configs.c_cflag |= PARENB; // Parity enable
//configs.c_cflag &= ~PARODD; // Even Parity
configs.c_cflag &= ~PARENB; // Parity disable
}
configs.c_cflag &= ~CSTOPB; // 1 stop bit
//configs.c_cflag |= CSTOPB; // 2 stop bit
configs.c_cflag &= ~CSIZE;
configs.c_cflag |= CS8; // 8-bit data
configs.c_cflag &= ~CRTSCTS; // Disable hardware flow control
// Setting Local Mode
configs.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG); //RAW input
// Setting Input mode
configs.c_iflag |= INPCK; // Enabling Parity Check
configs.c_iflag &= ~ISTRIP; // Disable strip off 8th bit when received
configs.c_iflag &= ~(IXON | IXOFF | IXANY); // Disable software flow control
// Setting Output Mode
configs.c_oflag &= ~OPOST; // RAW output
// Setting Control chars
configs.c_cc[VTIME] = 0; // Timeout in 0.1s, 0 (no timeout)
configs.c_cc[VMIN] = 0;
tcflush(fd, TCIFLUSH); // clean line
if (tcsetattr(fd, TCSANOW, &configs)!=0) {
fprintf(stderr, "ERROR ! Unable to write configuration to hardware\n");
}
}
int main(int argc, char **argv) {
FILE *fdata;
int comm, count,n;
unsigned char i;
fd_set read_fd;
struct timeval tv;
tv.tv_sec=0;
tv.tv_usec=100;
unsigned char test[10];
//Open serial port
fd = open_port();
//Initialize serial
init_port(fd);
int fd0, retval;
struct timeval tv0, tv1;
gettimeofday(&tv0, NULL);
printf("start reading..\n");
while(1) {
gettimeofday(&tv1, NULL);
fcntl(fd, F_SETFL, FNDELAY); // set reading as non blocking
n=read(fd, &test, 10); // return -1 in version 1.7.10 and up
if (n>0) {
printf("%d, ",(tv1.tv_sec-tv0.tv_sec)*1000+(tv1.tv_usec/1000-tv0.tv_usec/1000));
printf("read (%d bytes) : ", n);
for (i=0;i<n;i++)
printf("%x ", test[i]);
printf("\n");
} else
printf("%d \n",n);
}
close(fd);
return 0;
}
-------------- next part --------------
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