Hello fox guys,
I wrote a simple shell script, which allows to read out the most
important gps-parameters from the nmea-message, received by the gps-mouse:
file: "gps_d"
-----------------------snip-----------------------
#!/bin/sh
# The script is made by gazoox - don't remove this line ;)
# stty xxx xxx Configure your serial-Port if needed!
gps=/dev/ttyUSB0
echo "?" > /var/gps_latitude
echo "?" > /var/gps_longitude
echo "?" > /var/gps_altitude
echo "?" > /var/gps_sats_in_view
echo "?" > /var/gps_heading
echo "?" > /var/gps_speed
echo gazoox greets you --> gps_Deamon started
while true;
do
awk -F , '$1=="$GPGGA" {print}' $gps | head -n 1 > /var/gps_GPGGA
awk -F , '$1=="$GPRMC" {print}' $gps | head -n 1 > /var/gps_GPRMC
echo
echo
echo --------------------------
echo : $(cat /var/gps_GPGGA)
echo : $(cat /var/gps_GPRMC)
# echo $(awk -F , '$1=="$GPGGA" {print $2}' /var/gps_GPGGA)
# echo $(awk -F , '$1=="$GPRMC" {print $2}' /var/gps_GPRMC)
awk -F , '$1=="$GPRMC" {print $3}' /var/gps_GPRMC > /var/gps_valid
good_pos=$(cat /var/gps_valid)
case $good_pos in
V) echo GPS Data is NOT VALID !!!
echo "?" > /var/gps_latitude
echo "?" > /var/gps_longitude
echo "?" > /var/gps_altitude
awk -F , '$1=="$GPGGA" {print $8}' /var/gps_GPGGA >
/var/gps_sats_in_view >
echo "?" > /var/gps_heading
echo "?" > /var/gps_speed
;;
A) # echo GPS Data is valid
awk -F , '$1=="$GPGGA" {print $3 $4}' /var/gps_GPGGA >
/var/gps_latitude
awk -F , '$1=="$GPGGA" {print $5 $6}' /var/gps_GPGGA >
/var/gps_longitude
awk -F , '$1=="$GPGGA" {print $10 $11}' /var/gps_GPGGA >
/var/gps_altitude
awk -F , '$1=="$GPGGA" {print $8}' /var/gps_GPGGA >
/var/gps_sats_in_view
awk -F , '$1=="$GPRMC" {print $9}' /var/gps_GPRMC >
/var/gps_heading
awk -F , '$1=="$GPRMC" {print $8}' /var/gps_GPRMC >
/var/gps_speed
;;
esac
echo
echo lat_________: $(cat /var/gps_latitude)
echo lon_________: $(cat /var/gps_longitude)
echo altitude____: $(cat /var/gps_altitude)
echo sats_in_view: $(cat /var/gps_sats_in_view)
echo heading_____: $(cat /var/gps_heading)°
speed=$(cat /var/gps_speed)
if [ "$speed" = "" ]; then
speed=0
fi
echo speed_______: $speed knots
sleep 1
done
exit 0
-----------------------snip-----------------------
It works with my USB-mouse with an pl-2302 serial to usb
changer, but should work with all standard gps-mice (serial or usb
with fox-supported usb-serial chips).
A few notes and explanations:
1)
First, you should check on wich device the data is received. Check
/dev/ttyUSB[x] or the serials on /dev/ttyS[x]. You can print the data
via "cat /dev/ttyUSB0" for example. If you connect a serial mouse,
configure the serial port with "stty" first.
2)
Make your "stty" entry in the script, if needed.
3)
gps=... must represent your correspondenting device
4)
The script is running in an endless loop. Each data line is checked
via "awk". The each data is writen into a separate file which includes
the parameter in readable ascii. (The /var directory is in the ram,
not in flash!). A little bit tricky was to recognize the lines and
then move the SINGLE message line to a separate file for extracting
the parameters in the next step. When you use "cat /dev/ttyUSB0" for
example, a EOF-signal (end of file) is never received...
5)
You can run the script as a background task with "gps_d &". You can
remove the echo lines or start it with "gps_d > /dev/null &" if you
don't want a console output.
6)
-->When the script runs in backgroung, you can access and use the
parameter files (/var/gps_xxxx) in your own scripts, compiled c
programs or even in a html script from the webbrowser.
In the shell you could use it with "cat /var/gps_xxxx"
7)
The processing of the NMEA-data lines are optimized for my
gps-mouse. Note that awk is waiting for the GPGGA and then for the
GPRMC line before the results are written in the parameter files.
Perhaps you can get a faster processing if you swap the first two
lines ("awk...") after the do command.
8)
For starting the script automatically after booting up, include a
small startup script in /etc/init.d/boottime. All scripts in this
directory are runned after the boot process. Don't forget "chmod +x .."
for example:
--snip--
#!/bin/sh
exec /mnt/1/my_deamons/gps_d > /dev/null &
exit 0
--snip--
9)
The skript works not realy in realtime, but fast enough. Even the
gps-mouse sends only one gps coordinate every second. Faster update
rates are not usual with the cheap ones.
Have fun!
I spend much time on my "foxboard project", so please leave a comment
if this HowTo was helpfull for you.
Greetings
gazoox
