28 Jul 2016
ppscheck
8
The GPSD Project
GPSD Documentation
ppscheck
tool to check a serial port for PPS
ppscheck
-h
-V
device
DESCRIPTION
ppscheck watches a specified serial port for transitions that
might be PPS. It looks for changes in handshake lines CD, RI, and CTS
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.
To check the first serial port do this:
ppscheck /dev/ttyS0
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.
The program accepts the following options:
-h
Display help message and terminate.
-V
Dump version and exit.
The "device" argument should be the pathname of a device. It will
be the device monitored.
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 aserted.
If you don't see output within a second, use gpsmon 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 DCD. 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
1 if the device counld not be opened. 0 otherwise
SEE ALSO
gpsd8.
AUTHOR
Eric S. Raymond esr@thyrsus.com.