ppscheck(8) GPSD Documentation ppscheck(8)
NAME
ppscheck - tool to check a serial port for PPS
SYNOPSIS
ppscheck [-?] [--help] [-p] [--pps] [--version] [-h] [-V]
ppscheck [-m] device
DESCRIPTION
ppscheck watches a specified serial port for transitions that might be
PPS. It looks for changes in handshake lines CD, CTS, DSR, and RI by
running ioctl(...., TIOCMIWAIT, ...) in a loop. When it sees a state
change it emits a timestamped line of output dumping the state of the
handshake signals. It's useful for checking whether a device is emitting
PPS.
ppscheck can run as a normal user, but that user must have permissions to
read the target device. Running under sudo may, or may not, work.
Running as root will always work.
To check the first serial port do this:
# ppscheck /dev/ttyS0
As a side effect, ppscheck will try to create the matching /dev/ppsX by
setting the tty line discipline (ldisc) to N_PPS (18). You should then
have a device /dev/pps0. Note that not all serial devices support ldisc
N_PPS.
You can now use ppscheck to see if the KPPS (RFC 2783) interface is
working:
# ppscheck /dev/pps0
ppscheck is not intended for routine use, but rather for diagnostic
purposes. Once you have verified a particular device can output PPS
signals you will never need to use it again on that device.
OPTIONS
The program accepts the following options:
-?+, `+-h+, `+--help
Print help message, then exit.
-m+, `+--match
Find PPS device that matches device.
-p+, `+--pps
Print active PPS devices, then exit.
-V+, `+--version
Dump version, then exit.
-x SEC, --seconds SEC
Exit after delay of SEC seconds.
ARGUMENTS
The device argument should be the pathname of a device. Such as
/dev/ttyS0 or /dev/pps0. It will be the device monitored.
For a tty device, each output line is the second and nanosecond parts of
a timestamp followed by the names of the handshake signals then asserted.
Off transitions may generate lines with no signals asserted.
For a pps device, each output line will contain the assert and clear
times last detected by KPPS.
If you don't see output within a second, use cgps, xgps, or some other
equivalent tool to check that your device has a satellite lock and is
getting 3D fixes before giving up on the possibility of PPS.
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 CD.
Suspect this especially if the cable jacket looks too skinny to hold more
than three leads!
Most GPS that have built in USB do not support PPS. When in doubt,
contact the vendor for confirmation that your device does supply PPS.
RETURN VALUES
0
OK
1
if the device counld not be opened, or some other failure
SEE ALSO
cgps(1), xgps(1), gpsd(8)
RESOURCES
Project web site: <https://gpsd.io/>
COPYING
This file is Copyright 2013 by the GPSD project
SPDX-License-Identifier: BSD-2-clause
AUTHOR
Eric S. Raymond
GPSD, Version 3.24 2022-04-27 ppscheck(8)
mgpsd 3.24 - Generated Sun Jan 1 13:25:17 CST 2023