How was this demo created?

This demo was created in just a few minutes using a few simple tools (learn more -- including a demonstration video -- Here):

The GP3 Hardware interface
An LM34 temperature sensor
The free GP3EZ software
Free Cygwin software (allows Linux-style scripting for Windows)

If the temperature is not updating, that means I am not running the software at the moment.

The GP3EZ lets you develop applications for the GP3 with a "point and click" interface. You can see the screen shots on the link above. However, GP3EZ can also export scripts to HTML. The script that is running this demo looks like this:

Examples\webtemp.gp3

This is the Cygwin/Web Temperature demo. LM34 hooked up to AN2.

Step #	Tag	Condition	Action	Next	Notes
1	Start	(wait) Analog 2>0 V	External New File: c:\gp3temp.txt		This will always trigger.
2	pause	(wait) After 10000 ms			Wait 10 sec.
3		(wait) Analog 2>0 V	External Add File: c:\gp3temp.txt	pause	This will always trigger.

Step 1 reads the voltage from the LM34 and writes it to a new file. Then the script pauses for 10 seconds and makes more readings, adding them to the file.

The file looks like this:

1/9/2008 7:24:33 AM,0.7373047,Start,{none}
1/9/2008 7:24:43 AM,0.7373047,3,{none}
1/9/2008 7:24:53 AM,0.7373047,3,{none}
1/9/2008 7:25:03 AM,0.7421875,3,{none}
1/9/2008 7:25:13 AM,0.7373047,3,{none}

The first two fields are what we are interested in: the date/time and the LM34 voltage (10mV = 1 degree). The other two fields are the step name or number, and the current GP3EZ state (which isn't used in this script). Note that readings taken by different steps could be distinguished (if you wanted to display multiple values). Keep in mind that the readings are 10 bit accurate, so the number of significant digits computed ought to be adjusted during calcuation (although this simple demo doesn't do that).

Now we just need a cygwin script (gp3temp.sh):

#!/bin/bash
# Be sure to execute chmod +x gp3temp.sh once to make
# the script executable
while true
do
  # read the last line from the file and "awk" it
  tail -n1 /c/gp3temp.txt | awk -f gp3temp.awk >/c/gp3temp.html
  # copy file to Web server
  scp gp3temp.html awce:public_html/gp3ez
  sleep 30   # wait 30 seconds
done

That's easy enough. Awk processess the last line of the file and then scp sends it to the Web server. You could use FTP, rsync, or however you normally send things to your Web server. If you run a local Web server, it could be a simple file copy.

So what's in the Awk script? Easy:

BEGIN {
  FS=",";
  print "<HTML><HEAD><META HTTP-EQUIV='REFRESH' CONTENT='60'>\n";
  print "<TITLE>GP3 Temperature Demo</TITLE>";
  print "</HEAD><BODY BGCOLOR=CORNSILK>";
}

/^[0-9]/ {
  xtemp=$2*100;  # 10mV/degree
  print "<H1>At " $1 " the temperature at AWC was "  xtemp "F";
}

END {
  print "</BODY></HTML>";
  }

Most of this is just spitting out generic HTML. The only real work is computing the actual temperature (xtemp=$2*100). Awk splits the lines into fields (in this case, on the commas) so $1 is the date/time and $2 is the voltage.