Make ppcheck a full fledged program, with man page.

This tool makes it easy for the newbie to unambiguous verify that
his GPS has PPS.

1 files changed, 131 insertions, 0 deletions

diff --git a/ppscheck.c b/ppscheck.c
new file mode 100644
index 00000000..c0b49f6a
--- /dev/null
+++ b/ppscheck.c
@@ -0,0 +1,131 @@
+/*
+ * 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 <stdlib.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"},
+};
+
+void usage(void)
+{
+	fprintf(stderr, "usage: ppscheck [-h] [ -V] <device>\n");
+	fprintf(stderr, "                 -h   print usage\n");
+	fprintf(stderr, "                 -V   print cwVersion\n");
+	exit(1);
+}
+
+int main(int argc, char *argv[])
+{
+    struct timespec ts;
+    int fd;
+    int c;
+
+    while((c = getopt(argc, argv, "hV")) != -1) {
+	    switch(c){
+	    case 'h':
+	    default:
+		usage();
+		exit(0);
+	    case 'V':
+		(void)printf("%s: %s\n", argv[0], "3.17");
+		exit(EXIT_SUCCESS);
+	    }
+    }
+    argc -= optind;
+    argv += optind;
+
+    if (argc != 1)
+	    usage();
+
+    fd = open(argv[0], O_RDONLY);
+
+    if (fd == -1) {
+	(void)fprintf(stderr,
+		      "open(%s) failed: %d %.40s\n",
+		      argv[0], errno, strerror(errno));
+	exit(1);
+    }
+
+    (void)fprintf(stdout, "# Seconds  nanoSecs   Signals\n");
+    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 %09ld", 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 */