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/*
* Watch a specified serial port for transitions that might be 1PPS.
*
* Each output line is the second and nanosecond parts of a timestamp
* followed by the names of handshake signals then asserted. Off
* transitions may generate lines with no signals aserted.
*
* If you don't see output within a second, use gpsmon or some other
* equivalent tool to check that your device has satellite lock and is
* getting fixes before giving up on the possibility of 1PPS.
*
* Also, check your cable. Cheap DB9 to DB9 cables such as those
* issued with UPSes often carry TXD/RXD/GND only, omitting handshake
* lines such as DCD. Suspect this especially if the cable jacket
* looks too skinny to hold more than three leads!
*
* This code requires only ANSI/POSIX. If it doesn't compile and run
* on your Unix there is something very wrong with your Unix.
*
* This code by ESR, Copyright (C) 2013, under BSD terms.
*/
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h> /* needed for open() and friends */
#include <sys/ioctl.h>
#include <errno.h>
#include <time.h>
struct assoc {
int mask;
char *string;
};
/*
* Possible pins for PPS: DCD, CTS, RI, DSR. Pinouts:
*
* DB9 DB25 Name Full name
* --- ---- ---- --------------------
* 3 2 TXD --> Transmit Data
* 2 3 RXD <-- Receive Data
* 7 4 RTS --> Request To Send
* 8 5 CTS <-- Clear To Send
* 6 6 DSR <-- Data Set Ready
* 4 20 DTR --> Data Terminal Ready
* 1 8 DCD <-- Data Carrier Detect
* 9 22 RI <-- Ring Indicator
* 5 7 GND Signal ground
*
* Note that it only makes sense to wait on handshake lines
* activated from the receive side (DCE->DTE) here; in this
* context "DCE" is the GPS. {CD,RI,CTS,DSR} is the
* entire set of these.
*/
const static struct assoc hlines[] = {
{TIOCM_CD, "TIOCM_CD"},
{TIOCM_RI, "TIOCM_RI"},
{TIOCM_DSR, "TIOCM_DSR"},
{TIOCM_CTS, "TIOCM_CTS"},
};
int main(int argc, char *argv[])
{
struct timespec ts;
int fd = open(argv[1], O_RDONLY);
if (fd == -1) {
(void)fprintf(stderr,
"open(%s) failed: %d %.40s\n",
argv[1], errno, strerror(errno));
return 1;
}
for (;;) {
if (ioctl(fd, TIOCMIWAIT, TIOCM_CD|TIOCM_DSR|TIOCM_RI|TIOCM_CTS) != 0) {
(void)fprintf(stderr,
"PPS ioctl(TIOCMIWAIT) failed: %d %.40s\n",
errno, strerror(errno));
break;
} else {
const struct assoc *sp;
int handshakes;
(void)clock_gettime(CLOCK_REALTIME, &ts);
(void)ioctl(fd, TIOCMGET, &handshakes);
(void)fprintf(stdout, "%10ld %10ld", ts.tv_sec, ts.tv_nsec);
for (sp = hlines;
sp < hlines + sizeof(hlines)/sizeof(hlines[0]);
sp++)
if ((handshakes & sp->mask) != 0) {
(void)fputc(' ', stdout);
(void)fputs(sp->string, stdout);
}
(void)fputc('\n', stdout);
}
}
}
/* end */
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