1PPSCHECK(8)                   GPSD Documentation                   PPSCHECK(8)
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NAME

6       ppscheck - tool to check a serial port for PPS
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SYNOPSIS

9       ppscheck [-?] [--help] [-p] [--pps] [--version] [-h] [-V]
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11       ppscheck [-m] device
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DESCRIPTION

14       ppscheck watches a specified serial port for transitions that might be
15       PPS. It looks for changes in handshake lines CD, CTS, DSR, and RI by
16       running ioctl(...., TIOCMIWAIT, ...) in a loop. When it sees a state
17       change it emits a timestamped line of output dumping the state of the
18       handshake signals. It’s useful for checking whether a device is
19       emitting PPS.
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21       ppscheck can run as a normal user, but that user must have permissions
22       to read the target device. Running under sudo may, or may not, work.
23       Running as root will always work.
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25       To check the first serial port do this:
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27           # ppscheck /dev/ttyS0
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29       As a side effect, ppscheck will try to create the matching /dev/ppsX by
30       setting the tty line discipline (ldisc) to N_PPS (18). You should then
31       have a device /dev/pps0. Note that not all serial devices support ldisc
32       N_PPS.
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34       You can now use ppscheck to see if the KPPS (RFC 2783) interface is
35       working:
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37           # ppscheck /dev/pps0
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39       ppscheck is not intended for routine use, but rather for diagnostic
40       purposes. Once you have verified a particular device can output PPS
41       signals you will never need to use it again on that device.
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OPTIONS

44       The program accepts the following options:
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46       -?+, `+-h+, `+--help
47           Print help message, then exit.
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49       -m+, `+--match
50           Find PPS device that matches device.
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52       -p+, `+--pps
53           Print active PPS devices, then exit.
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55       -V+, `+--version
56           Dump version, then exit.
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58       -x SEC, --seconds SEC
59           Exit after delay of SEC seconds.
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ARGUMENTS

62       The device argument should be the pathname of a device. Such as
63       /dev/ttyS0 or /dev/pps0. It will be the device monitored.
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65       For a tty device, each output line is the second and nanosecond parts
66       of a timestamp followed by the names of the handshake signals then
67       asserted. Off transitions may generate lines with no signals asserted.
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69       For a pps device, each output line will contain the assert and clear
70       times last detected by KPPS.
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72       If you don’t see output within a second, use cgps, xgps, or some other
73       equivalent tool to check that your device has a satellite lock and is
74       getting 3D fixes before giving up on the possibility of PPS.
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76       Check your cable. Cheap DB9 to DB9 cables such as those issued with
77       UPSes often carry TXD/RXD/GND only, omitting handshake lines such as
78       CD. Suspect this especially if the cable jacket looks too skinny to
79       hold more than three leads!
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81       Most GPS that have built in USB do not support PPS. When in doubt,
82       contact the vendor for confirmation that your device does supply PPS.
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RETURN VALUES

85       0
86           OK
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88       1
89           if the device counld not be opened, or some other failure
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SEE ALSO

92       cgps(1), xgps(1), gpsd(8)
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RESOURCES

95       Project web site: https://gpsd.io/
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COPYING

98       This file is Copyright 2013 by the GPSD project
99       SPDX-License-Identifier: BSD-2-clause
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AUTHOR

102       Eric S. Raymond
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106GPSD, Version 3.25                2023-01-10                       PPSCHECK(8)