Arduino board connected to router.
6 analog inputs, 2 relay outputs, software counter  


Example for data  sent over serial interface every second:

6 analog inputs. Can connect to it PIR motion detector. 

Software counter. For counting Geiger counter clicks.

Watchdog count. If Arduino has not received a command to clear watchdog for 5 min it disconnects router power for a second. Effective to keep router from hanging.  

Status of second relay  for switching on/off 220V lamp over internet, to impress people.



My experience. 
Need Arduino with old type of USB interface chip. The new are not recognized by 
Linux. Buy Duemilanove! 
Arduino hangs router if connected via serial port of the router. 
May be speed is wrong. Played around, but could not solve problem. 
Started to use USB-serial adapter. Communication with Arduino works. Do not neeed to set speed. 

--------------------------------------------------------
Some code concerning serial port, but not necessary fot USB-serial adapter. 

lsdev install
apt-get install procinfo

com port speed 
http://uavideas.blogspot.com/2009/03/change-serial-port-speed-on-openwrt.html

opkg install coreutils
does not work 

cd /home 
wget http://bobo.bash.fi/stty
./stty -F /dev/ttyS0 9600

opkg install kmod-usb-core kmod-usb-ohci kmod-usb-serial kmod-usb-serial-ftdi kmod-usb2 
http://www.arduino.cc/playground/Italiano/Avrdude-openwrt

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########################################################
# Arduino analog input as a software counter, 
# for example motion detector, Geiger counter, electricity meter, etc. 
# Program run in loop check Arduino serial output
########################################################
c1=$(cat /www/test1)
while (true)
do
sleep 1
a=$(head -2 /dev/ttyUSB0)
echo $a
set -- $a
t1=$1
if [ $t1 -gt 500 ]; then
echo "alarm" $t1
c1=$(($c1+300))

echo $c1

else echo "quiet" $t1
fi

#rrdtool update /www/counts.rrd  N:$c1;

echo $c1 > /www/test1
done



##################################
#Once in 5 min 
##################################

c1=$(cat /www/test1)
rrdtool update /www/counts.rrd  N:$c1;



# creates fraphs for motion detector click database



rrdtool graph /www/counts1.png --start -1d --end now \
--vertical-label "Motion detected" -a PNG \

--upper-limit 30 --lower-limit 0  --rigid  \
DEF:temp1=/www/counts.rrd:c1:AVERAGE \
LINE1:temp1#FF0000:"c1" \
GPRINT:temp1:LAST:"Last CPM\: %3.0lf"



rrdtool graph /www/counts2.png --start -1w --end now \

--vertical-label "Motion detected" -a PNG \

--upper-limit 30 --lower-limit 0  --rigid  \
DEF:temp1=/www/counts.rrd:c1:AVERAGE \

LINE1:temp1#FF0000:"c1"