Simple Kindle Temperature Display 
Thursday, February 7, 2013, 12:41
Posted by Administrator
I've been wanting to make an e-paper temperature display ever since seeing the beautiful weather forecast display that Matthew Petroff put together but as is my style I wanted to do something much simpler and easier to get running. My main self imposed requirement was to make something that would work on an unrooted device. With my kindle touch laying around mostly unused the last few weeks I finally got determined to put it to some better use around the apartment.

I started off with my old weather grabbing script to pull the current temperature information from Wunderground. Wunderground claims to be phasing out their API that I like, but it shouldn't be difficult to scrape another site once they finally can it. I cut out a lot of the extra information I had been grabbing before since I wanted to dedicate this display to just temperature information.

The revised bash script follows below:

# Temperature Grabbing Bash Script From Wunderground
# Created by Spike Snell 2013

# Make sure there is an argument which could have a zip
if [ $# -lt 1 ] ; then
echo "Please include a zipcode as an argument such as: ./ 72703"
exit 1

# Grab the Zipcode from the command line argument


# Grab the content from the Wunderground API
weather_wget=`wget -q $url -O -`
weather_xml=`echo "$weather_wget" | sed 's/<current_observation>.*//'`
weather=`echo "$weather_xml" | sed 's/></>\n</g'`

# Get the temperature in C
temp=`echo "$weather" | grep -e '<temp_c>' | \
sed -e 's/\t\t<temp_c>//' -e 's/<\/temp_c>//'`

# Print out all the information
echo $temp

# Write it to a gif
echo $temp | convert -pointsize 555 text:- n.gif

The biggest change in the code from the old one is that I'm now using imagemagick to do a convert on the temperature text into a gif file. This is because I found that the kindle's experimental web browser was very iffy about displaying very large fonts, it would work about 1/10th of the time. It was able to display a large picture great though.

This whole project was made much simpler than Matthew's by driving the process with the kindle's built in web browser. I have a server running a lamp stack that I like to use and put the previous shell script and the following php code up on.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "">
<meta http-equiv="refresh" content="360" charset=UTF-8">
<META NAME="DESCRIPTION" CONTENT="A small temperature indicator to run as an art piece displaying degrees C.">
<META NAME="KEYWORDS" CONTENT="temperature,art,large,tool">
<title>Current Local Temperature Indicator</title>
<body bgcolor="#FFFFFF">
$z = 72703;
if (isset($_GET['z'])) {
$z = $_GET['z'];
$t = `./ $z`;
# convert to F
$f = $t*9/5+32;
echo $f;
<img src="n.gif">

All that was left to do was to point the kindle's browser towards the php file, this triggers the bash script, writes the image and does a simple conversion of C -> F degrees to display above the large C readout. Voila! A temperature readout, self updating every 6 minutes with a meta refresh. So now everything is finished, except the kindle has one last gotcha, it blanks the screen and displays a screensaver after about a 15 minute inactivity period. Luckily this can be easily disabled. At the home screen of the kindle you can enter "~ds". This will disable the screensaver until the device is restarted.

Now some glamour shots of the kindle temperature display in operation, along with a closeup of my tacky wall-mounting job.

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