GpsService

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Creating a script

In order to keep a bluetooth GPS unit connected to the gumstix we need a script which watches the bluetooth connection and re-establishes it if the gpsd loses the connection. The following shell script does just that:

#!/bin/sh
# Use "hcitool scan" to find out the MAC address
GPS_MAC=00:11:67:80:75:F4
# Use "sdptool browse GPS_MAC_ADDRESS" to find out the channel (it is listed
# in a line beginning with RFCOMM) after you know the MAC address
SERIAL_PORT_CHANNEL=1
while true; do
        # Kill old gpsd instances
        echo "Killing all gpsd"
        killall gpsd;
        sleep 2;
        killall -9 gpsd
        # Add a new Serial Port service, in order to keep the original Serial Port unaffected
        # Local services can be displayed with: sdptool browse ff:ff:ff:00:00:00
        echo "Adding a new serial port"
        sdptool del 0x10001 > /dev/null
        if sdptool add --channel=2 SP; then
                echo "Adding SP successful";
        else
                echo "Adding failed";
                sleep 10;
                continue;
        fi
        sdptool setattr 0x010000 0x100 "Ch 1 Serial (getty)" > /dev/null
        sdptool setattr 0x010001 0x100 "Ch 2 Serial (GPS)" > /dev/null
        # Scanning for gps
        echo "Scanning for GPS";
        while ! hcitool scan | grep $GPS_MAC > /dev/null; do
                sleep 10;
                echo "Scanning for GPS";
        done
        echo "GPS with MAC $GPS_MAC found"
        # Try to bind channel 1 (/dev/rfcomm1) to the GPS serial port
        while ! rfcomm | grep $GPS_MAC | grep clean > /dev/null; do
                echo "Establishing channel to GPS"
                rfcomm release 1
                rfcomm bind 1 $GPS_MAC $SERIAL_PORT_CHANNEL
                sleep 2
        done
        echo "Starting gpsd"
        gpsd -n /dev/rfcomm1
        echo "Waiting for gpsd to get connected";
        sleep 20
        if rfcomm | grep $GPS_MAC | grep connected > /dev/null; then
                echo "GPS connected, going into watchdog mode"
        fi
        while rfcomm | grep $GPS_MAC | grep connected > /dev/null; do
                sleep 10
        done
        echo "gpsd disconnected";
done

Just adjust GPS_MAC to fit your GPS (use "hcitool scan" to find out the address). This script only works for bluetooth GPS devices which do not require a PIN code. You can save it under /usb/bin/gps_service and run it at startup. Please not that I had problems to connect to my GPS while being connected to the gumstix via bluetooth.