Setting up the GPS
I have been lucky on this.
Apart from the Adafruit Ultimate GPS I recently purchased, I did find in my drawers a
couple more:
As shown in this photo, apart of the Adafruit GPS, I also had a choice from a Garmin 18-5, a 5 Hz device with serial TTL output and a 1-Hz OEM USB GPS,
I decided to use the USB unit because:
A. since the speed -in absolute terms- I will be moving with is low, 1 GPS sample per second is more than sufficient.
B. The USB GPS has a long cable, long enough to put it out of the window now that I am doing the development, something that enables the system to get a fix!
Setting it up was plain simple:
1. Installed the required packages:
The setup was verified using the following command:
This produced the following result:
Which mean that the GPS works and communicates with the Raspberry.
Further tests where conducted using Python:
gpsd documentation can be found at gpsd home, and a quickstart how-to can be seen here.
At this document one can find info on the gpsd report structure which has as follows:
For example, the following code
produces this output:
This concludes post "Setting up the GPS".
Additional details will be found in future post with title something in the line of "GPS Software"
References:
GPSD Home
GPSD Client HOWTO
GPSD Result Structures
The Architecture of Open Source Applications, GPSD
GPS Protocol Reference Manual
UPDATE:
After rebooting the Raspberry PI, gpsd didn't seem to work.
I did some debuging using
The same time gpsd daemon was running and hooked to TCP port 2947.
I killed the process and started it again manually giving
Reboot caused once again the same issue.
I check the default gpsd config (cat /etc/default/gpsd) but looked OK.
I reconfigured the gpsd using "dpkg-reconfigure gpsd" but on reboot I had the same issue.
I decided to take matters in hand, "runlevel" indicated the Raspberry was running in level 2.
I deleted the S04gpsd file from /etc/rc2.d (a link to /etc/init.d/gpsd) and added the above command ("/usr/sbin/gpsd -n -F /var/run/gpsd.sock -P /var/run/gpsd.pid /dev/ttyUSB0" to the end of the /etc/rc.local file.
Now the system works everytime.
It's probably a quick and dirty solution but for the time being it works.
The actual solution to the initial problem came by adding the -n flag ("don't wait for client connect to poll GPS") to the gpsd initialization.
UPDATE 2:
few more problems with gpsd, sometimes after reboot, gpsd was running but gpsd.pid had wrong id.
Quick and dirty solution by removing the line
I have been lucky on this.
Apart from the Adafruit Ultimate GPS I recently purchased, I did find in my drawers a
couple more:
I decided to use the USB unit because:
A. since the speed -in absolute terms- I will be moving with is low, 1 GPS sample per second is more than sufficient.
B. The USB GPS has a long cable, long enough to put it out of the window now that I am doing the development, something that enables the system to get a fix!
Setting it up was plain simple:
1. Installed the required packages:
sudo apt-get install gpsd gpsd-clients python-gps2. Associate gpsd with the physical GPS device:
sudo gpsd /dev/ttyUSB0 -F /var/run/gpsd.sock
The setup was verified using the following command:
cgps -s
This produced the following result:
Further tests where conducted using Python:
#!/usr/bin/python
import gps
session = gps.gps("localhost", "2947")
session.stream(gps.WATCH_ENABLE | gps.WATCH_NEWSTYLE)
while True:
try:
report = session.next()
print report
except KeyError:
pass
except KeyboardInterrupt:
quit()
except StopIteration:
session = None
print "GPSD has terminated"
gpsd documentation can be found at gpsd home, and a quickstart how-to can be seen here.
At this document one can find info on the gpsd report structure which has as follows:
| Name | Always? | Type | Description |
|---|---|---|---|
| class | Yes | string | Fixed: "TPV" |
| tag | No | string | Type tag associated with this GPS sentence; from an NMEA device this is just the NMEA sentence type. |
| device | No | string | Name of originating device. |
| mode | Yes | numeric | NMEA mode: %d, 0=no mode value yet seen, 1=no fix, 2=2D, 3=3D. |
| time | No | string | Time/date stamp in ISO8601 format, UTC. May have a fractional part of up to .001sec precision. May be absent if mode is not 2 or 3. |
| ept | No | numeric | Estimated timestamp error (%f, seconds, 95% confidence). Present if time is present. |
| lat | No | numeric | Latitude in degrees: +/- signifies West/East. Present when mode is 2 or 3. |
| lon | No | numeric | Longitude in degrees: +/- signifies North/South. Present when mode is 2 or 3. |
| alt | No | numeric | Altitude in meters. Present if mode is 3. |
| epx | No | numeric | Longitude error estimate in meters, 95% confidence. Present if mode is 2 or 3 and DOPs can be calculated from the satellite view. |
| epy | No | numeric | Latitude error estimate in meters, 95% confidence. Present if mode is 2 or 3 and DOPs can be calculated from the satellite view. |
| epv | No | numeric | Estimated vertical error in meters, 95% confidence. Present if mode is 3 and DOPs can be calculated from the satellite view. |
| track | No | numeric | Course over ground, degrees from true north. |
| speed | No | numeric | Speed over ground, meters per second. |
| climb | No | numeric | Climb (positive) or sink (negative) rate, meters per second. |
| epd | No | numeric | Direction error estimate in degrees, 95% confidence. |
| eps | No | numeric | Speed error estinmate in meters/sec, 95% confidence. |
| epc | No | numeric | Climb/sink error estimate in meters/sec, 95% confidence. |
For example, the following code
#!/usr/bin/python
import gps
# Listen on port 2947 (gpsd) of localhost
session = gps.gps("localhost", "2947")
session.stream(gps.WATCH_ENABLE | gps.WATCH_NEWSTYLE)
while True:
try:
report = session.next()
# Wait for a 'TPV' report
if report['class'] == 'TPV':
print 'fix mode:', report.mode
print 'Course over ground, degrees from true north', report.track
print 'Speed over ground, meters per second', report.speed
print '-----------------------------------------------------------------'
except KeyError:
pass
except KeyboardInterrupt:
quit()
except StopIteration:
session = None
print "GPSD has terminated"
produces this output:
fix mode: 2This report says that we have 2D fix (possibly a result of not having a good view of the sky) and that we are stationary.
Course over ground, degrees from true north 0.0
Speed over ground, meters per second 0.0
-----------------------------------------------------------------
fix mode: 2
Course over ground, degrees from true north 0.0
Speed over ground, meters per second 0.0
-----------------------------------------------------------------
This concludes post "Setting up the GPS".
Additional details will be found in future post with title something in the line of "GPS Software"
References:
GPSD Home
GPSD Client HOWTO
GPSD Result Structures
The Architecture of Open Source Applications, GPSD
GPS Protocol Reference Manual
UPDATE:
After rebooting the Raspberry PI, gpsd didn't seem to work.
I did some debuging using
gpsmon /dev/ttyUSB0This showed that hardware-wise the GPS was working.
The same time gpsd daemon was running and hooked to TCP port 2947.
I killed the process and started it again manually giving
/usr/sbin/gpsd -n -F /var/run/gpsd.sock -P /var/run/gpsd.pid /dev/ttyUSB0gpsd & cgps got working.
Reboot caused once again the same issue.
I check the default gpsd config (cat /etc/default/gpsd) but looked OK.
I reconfigured the gpsd using "dpkg-reconfigure gpsd" but on reboot I had the same issue.
I decided to take matters in hand, "runlevel" indicated the Raspberry was running in level 2.
I deleted the S04gpsd file from /etc/rc2.d (a link to /etc/init.d/gpsd) and added the above command ("/usr/sbin/gpsd -n -F /var/run/gpsd.sock -P /var/run/gpsd.pid /dev/ttyUSB0" to the end of the /etc/rc.local file.
Now the system works everytime.
It's probably a quick and dirty solution but for the time being it works.
The actual solution to the initial problem came by adding the -n flag ("don't wait for client connect to poll GPS") to the gpsd initialization.
UPDATE 2:
few more problems with gpsd, sometimes after reboot, gpsd was running but gpsd.pid had wrong id.
Quick and dirty solution by removing the line
/usr/sbin/gpsd -n -F /var/run/gpsd.sock -P /var/run/gpsd.pid /dev/ttyUSB0and adding
pkill gpsdon the /etc/rc.local
service gpsd start
