sirfmon
1
23 Mar 2005
sirfmon
monitor a SiRF GPS
sirfmon
device
DESCRIPTION
sirfmon is a monitor that watches
packets coming from a SiRF GPS (the SiRF chipset is the one by far the
most commonly used in GPS mice and other consumer-grade GPSes, about
80% of them and rising in early 2005). This program is primarily
useful as a diagnostic aid for troubleshooting
gpsd problems; it deliberately uses decoder
logic that different from the decoder in the
gpsd SiRF driver, so behaviors that show up
in both are unlikely to be due to logic bugs in either.
The device argument should be the serial devicename associated
with the GPS; sirfmon will search for a
correct baud rate and lock on to it automatically.
Note that sirfmon will fail if
gpsd is running, and vice-versa. You will
probably need to be root to run this program.
After startup, the top part of the screen reports the contents
of several especially interesting packet types. The bottom half of
the screen is a scrolling hex dump of all packets the GPS is issuing.
Dump lines beginning >>> represent control packets sent to the
GPS.
To interpret what you see, you will need a copy of the
SiRF Binary Protocol Reference Manual.
COMMANDS
The following comands are available while
sirfmon is running:
n
Switch device to NMEA mode at current speed and exit.
b
Change baud rate.
c
Set (c1) or clear (c0) static navigation. The SiRF documentation
says Static navigation is a position filter designed to be used
with motor vehicles. When the vehicle's velocity falls below a
threshold, the position and heading are frozen, and velocity is set to
zero. This condition will continue until the computed velocity rises
above 1.2 times the threshold or until the computed position is at
least a set distance from the frozen place. The threshold velocity and
set distance may vary with software versions.
l
Start logging of packets to specified file. If logging is
enabled, turn it off.
s
Send hex bytes to device. Following the 's' you may type hex
digit pairs; end with a newline. These will become the payload of a
SiRF control packet shipped to the device.
t
Toggle navigation-parameter display mode. Toggles between
normal display and one that shows selected navigation parameters from
MID 19, including the Static Navigation bit toggled by the 'c' command.
Ctrl-S
Freeze display, suspend scrolling in debug window.
Ctrl-Q
Unfreeze display, resume normal operation.
BUGS AND LIMITATIONS
The logic for hunting the GPS's baud rate is vulnerable to
various sorts of RS232 flakiness. If it hangs for longer than a few
seconds, kill the program and restart.
SEE ALSO
gpsd8,
xgps1,
libgps3,
libgpsd3,
gpsprof1,
gpsfake1,
gnuplot1.
AUTHOR
Eric S. Raymond esr@thyrsus.com, based on code
originally by Rob Janssen, PE1CHL. This code is part of the gpsd
toolset; there is a project page for gpsd
here.