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How to use Pharos USB GPS (Microsoft Streets & Trips) with N800 & maemo mapper

Just in case someone else ends up with the Pharos USB GPS (the one that comes with Microsoft Streets & Trips with GPS). This device is a USB-only GPS receiver powered by SIRF III technology. It reads model no. GPS-500 and part no. X13-51914.

Instead of buying a separate Bluetooth dock, I thought I would try and make use of the USB host mode that comes with OS versions chinook and up. A specially modified adapter does the specific trick of automatically switching the USB mode.

The Pharos USB GPS-500 receiver has a built-in Prolific USB-serial interface. N800 however does not come with the necessary modules and drivers to perform USB-serial interfacing. Fanoush was kind enough to make available a module pack (tar.gz) (see also this post) containing suitable modules: usbserial.ko and pl2303.ko under drivers/usb/serial. These of course will have to be loaded with insmod from the root account. Upon successfully insmodding, a new /dev/ttyUSB0 serial device is created.

One last trick I had to figure out was a hidden file called /var/lib/gps/.gps_no_serial_ports which will prevent maemo-mapper and the built-in gpsd daemon from accessing /dev/ttyUSB0. Once you remove that file everything should work like a charm.

The following steps are involved:

Code:

# insert kernel modules BEFORE connecting the dongle

insmod usbserial.ko # as root

insmod pl2303.ko    # as root

# this is when we connect the GPS dongle, wait ~10 seconds

chmod 666 /dev/ttyUSB0               # as root

rm /var/lib/gps/.gps_no_serial_ports # again as root

# the next step is probably not necessary

stty -F /dev/ttyUSB0 sane ; stty -F /dev/ttyUSB0 4800

Maemo-mapper will have to be configured to use the serial device /dev/ttyUSB0 under Settings/GPS/File Path. Make sure you write down the default /dev/pgps somewhere before replacing just in case it may prove critical some time in the future.

Cheers

Z

2/7/09 Edit: here is an implementation suggestion in conjunction with the Personal Menu app. A notable change from the example above is the use of gpsd as data source in maemo-mapper as opposed to pointing it to /dev/ttyUSB0. The scripts below will fire up gpsd with the right command-line options, This way several gps-enabled applications can run simultaneously.

Caution: some unix/linux skills are required, such as opening an xterm session, navigating the file system using cd and ls, copying and renaming files etc--

(1) I opened a Terminal session and created a new directory called /home/user/bin/usbser containing the following files; the .ko files are the new kernel modules described above:

Code:

start-gpsd    

restart-gpsd  

stop-gpsd

pl2303.ko     

usbserial.ko

The other 3 files are simple shell scripts as shown below:

start-gpsd

Code:

#!/bin/sh

echo do not connect the GPS dongle just yet. press enter when ready...

read x

killall gpsd && ( sleep 3 ; killall -9 gpsd ; sleep 3)

echo enabling usbserial module

lsmod | grep usbserial || ( insmod /home/user/bin/usbser/usbserial.ko ; sleep 3 )

echo enabling pl2303 module

lsmod | grep pl2303 || ( insmod /home/user/bin/usbser/pl2303.ko ; sleep 3 )

echo you can now connect the GPS dongle. press enter when ready...

read x

echo "/dev/ttyUSB0" > /var/lib/gps/gps_serial_ports

echo "/dev/pgps" >> /var/lib/gps/gps_serial_ports

echo --------------------------

echo modules that are now active

echo --------------------------

lsmod

echo --------------------------

chmod 666 /dev/ttyUSB0

stty -F /dev/ttyUSB0 sane

stty -F /dev/ttyUSB0 4800

rm /var/lib/gps/.gps_no_serial_ports

echo firing up gpsd

/usr/sbin/gpsd -n /dev/ttyUSB0

sleep 4

restart-gpsd

Code:

#!/bin/sh

killall gpsd && ( sleep 3 ; killall -9 gpsd ; sleep 3)

stty -F /dev/ttyUSB0 sane

stty -F /dev/ttyUSB0 4800

rm /var/lib/gps/.gps_no_serial_ports

echo firing up gpsd

/usr/sbin/gpsd -n /dev/ttyUSB0

sleep 4

stop-gpsd

Code:

#!/bin/sh

echo please remove the GPS dongle now. press enter when ready...

read x

killall gpsd && ( sleep 3 ; killall -9 gpsd ; sleep 3 )

echo disabling pl2303 module

lsmod | grep pl2303 && ( rmmod /home/user/bin/usbser/pl2303.ko ; sleep 3 )

echo disabling usbserial module

lsmod | grep usbserial && ( rmmod /home/user/bin/usbser/usbserial.ko ; sleep 3 )

echo ----------------------------

echo modules that are still active

echo ----------------------------

lsmod

echo ----------------------------

sleep 4

These scripts can be created on your PC using notepad then copied over a USB cable on the internal or external card. Then you could open a terminal session and copy the new files from either your external card (found at /media/mmc1) or internal (/media/mmc2). An alternative of course would be to create said shell scripts in vi or any other editor you may have available that can save plain text files (I for one use mc / mcedit).

With all files in place, I made the scritps executable: chmod +x *-gpsd.

(2) I installed Personal Menu. Then using the Edit Personal Menu option, I created entries for the scripts above and checked the "run as root" box; here are excerpts from my ~/.personal_menu.rc config file:

Code:

[1]

app name=engps

icon name=qgn_stat_gps_fix

executable=osso-xterm /home/user/bin/usbser/start-gpsd

run as root=true

run in term=false

service=



[2]

app name=disgps

icon name=qgn_stat_gps_no_fix

executable=osso-xterm /home/user/bin/usbser/stop-gpsd

run as root=true

run in term=false

service=



[3]

app name=regps

icon name=qgn_stat_gps_searching

executable=osso-xterm -e /home/user/bin/usbser/restart-gpsd

run as root=true

run in term=false

service=

(3) Logged in as root (see below posting from Aquabits describing how to do this,) I went ahead and added the following line to the bottom of /etc/sudoers:

Code:

user ALL = NOPASSWD: /usr/bin/osso-xterm

(4) One final step is to set maemo-mapper to use gpsd on localhost port 2947.

The "restart-gpsd" command above is sometimes useful when maemo-mapper is unable to locate the gps device; this most likely happens when the OS (stubbornly) recreates the .gps_no_serial_ports file.

Hope this helps

Cheers

Z.