Raspberry Pi and external MySQL

Question

I've follow this instructable: Web Control of Raspberry Pi GPIO.

It shows how to turn GPIO pins on or off through a simple web interface. Basically, a PHP file updates a local MySQL database with information about the pins (on or off) and a .sh file continusly reads the database to see if a pin should be turned on or off. Here is the .sh file:

# Script created by Daniel Curzon (http://www.instructables.com/member/drcurzon)
# Initial version created 10th June 2012
# Version: 1.0

###################################
#####  EDIT THESE BEFORE USE  #####
###################################
mysqlusername="USERNAME"
mysqlpassword="PASSWORD"

#############################################################################################################################
################################################### DO NOT EDIT BELOW THIS LINE ##############################################
##############################################################################################################################

#Set  Refresh
echo "How long do you want the wait time to be?          "
read waitTime

#Invoke GPIO
echo "4" > /sys/class/gpio/export
echo "17" > /sys/class/gpio/export
echo "18" > /sys/class/gpio/export
echo "21" > /sys/class/gpio/export
echo "22" > /sys/class/gpio/export
echo "23" > /sys/class/gpio/export
echo "24" > /sys/class/gpio/export
echo "25" > /sys/class/gpio/export

#Start Loop
while :
do
#Read MySQL Data
#Direction
direction4=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinDirection FROM pinDirection WHERE pinNumber='4'";)
direction17=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinDirection FROM pinDirection WHERE pinNumber='17'";)
direction18=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinDirection FROM pinDirection WHERE pinNumber='18'";)
direction21=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinDirection FROM pinDirection WHERE pinNumber='21'";)
direction22=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinDirection FROM pinDirection WHERE pinNumber='22'";)
direction23=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinDirection FROM pinDirection WHERE pinNumber='23'";)
direction24=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinDirection FROM pinDirection WHERE pinNumber='24'";)
direction25=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinDirection FROM pinDirection WHERE pinNumber='25'";)
#Status
status4=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinStatus FROM pinStatus WHERE pinNumber='4'";)
status17=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinStatus FROM pinStatus WHERE pinNumber='17'";)
status18=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinStatus FROM pinStatus WHERE pinNumber='18'";)
status21=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinStatus FROM pinStatus WHERE pinNumber='21'";)
status22=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinStatus FROM pinStatus WHERE pinNumber='22'";)
status23=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinStatus FROM pinStatus WHERE pinNumber='23'";)
status24=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinStatus FROM pinStatus WHERE pinNumber='24'";)
status25=$(mysql -B --disable-column-names --user=$mysqlusername --password=$mysqlpassword gpio -e "SELECT pinStatus FROM pinStatus WHERE pinNumber='25'";)

#Run Commands
if [ "$direction4" == "out" ]; then
    echo "out" > /sys/class/gpio/gpio4/direction
    if [ "$status4" == "1" ]; then
        echo "1" > /sys/class/gpio/gpio4/value
        echo "GPIO 4 Turned On"
    else
        echo "0" > /sys/class/gpio/gpio4/value
        echo "GPIO 4 Turned Off"
    fi
else
    echo "in" > /sys/class/gpio/gpio4/direction
fi
if [ "$direction17" == "out" ]; then
        echo "out" > /sys/class/gpio/gpio17/direction
    if [ "$status17" == "1" ]; then
                echo "1" > /sys/class/gpio/gpio17/value
                echo "GPIO 17 Turned On"
        else
                echo "0" > /sys/class/gpio/gpio17/value
                echo "GPIO 17 Turned Off"
        fi
else
        echo "in" > /sys/class/gpio/gpio17/direction
fi
if [ "$direction18" == "out" ]; then
        echo "out" > /sys/class/gpio/gpio18/direction
    if [ "$status18" == "1" ]; then
                echo "1" > /sys/class/gpio/gpio18/value
                echo "GPIO 18 Turned On"
        else
                echo "0" > /sys/class/gpio/gpio18/value
                echo "GPIO 18 Turned Off"
        fi
else
        echo "in" > /sys/class/gpio/gpio18/direction
fi
if [ "$direction21" == "out" ]; then
        echo "out" > /sys/class/gpio/gpio21/direction
    if [ "$status21" == "1" ]; then
                echo "1" > /sys/class/gpio/gpio21/value
                echo "GPIO 21 Turned On"
        else
                echo "0" > /sys/class/gpio/gpio21/value
                echo "GPIO 21 Turned Off"
        fi
else
        echo "in" > /sys/class/gpio/gpio21/direction
fi
if [ "$direction22" == "out" ]; then
        echo "out" > /sys/class/gpio/gpio22/direction
    if [ "$status22" == "1" ]; then
                echo "1" > /sys/class/gpio/gpio22/value
                echo "GPIO 22 Turned On"
        else
                echo "0" > /sys/class/gpio/gpio22/value
                echo "GPIO 22 Turned Off"
        fi
else
        echo "in" > /sys/class/gpio/gpio22/direction
fi
if [ "$direction23" == "out" ]; then
        echo "out" > /sys/class/gpio/gpio23/direction
    if [ "$status23" == "1" ]; then
                echo "1" > /sys/class/gpio/gpio23/value
                echo "GPIO 23 Turned On"
        else
                echo "0" > /sys/class/gpio/gpio23/value
                echo "GPIO 23 Turned Off"
        fi
else
        echo "in" > /sys/class/gpio/gpio23/direction
fi
if [ "$direction24" == "out" ]; then
        echo "out" > /sys/class/gpio/gpio24/direction
    if [ "$status24" == "1" ]; then
                echo "1" > /sys/class/gpio/gpio24/value
                echo "GPIO 24 Turned On"
        else
                echo "0" > /sys/class/gpio/gpio24/value
                echo "GPIO 24 Turned Off"
        fi
else
        echo "in" > /sys/class/gpio/gpio24/direction
fi
if [ "$direction25" == "out" ]; then
        echo "out" > /sys/class/gpio/gpio25/direction
    if [ "$status25" == "1" ]; then
                echo "1" > /sys/class/gpio/gpio25/value
                echo "GPIO 25 Turned On"
        else
                echo "0" > /sys/class/gpio/gpio25/value
                echo "GPIO 25 Turned Off"
        fi
else
        echo "in" > /sys/class/gpio/gpio25/direction
fi
#Complete Loop
sleep $waitTime
done

I want to control the GPIO outside my network, so I wanted to upload the database to a server and create a website to update it. However, I have no idea how to access an external MySQL database in the .sh file! How can I do it?

Answer 1

You can tell MySQL which host to connect to using the --host=<hostname> option. You might need to allow external connections on the server though.

Look at http://linux.die.net/man/1/mysql for more details. Scroll down to "--host".