Resurecting the Arduino/Xbee/Gumstix sensor network

About four years ago, I built a simple sensor network that used a couple of Arduinos, a Gumstix Linux mini computer and Xbee wireless that acted as an indoor-outdoor temperature display. A couple of years back, the outdoor part of the system stopped working. I poked it and prodded it and finally just decided the Arduino clone I was using had died.

Finally, after it had sat on my shelf for a couple of years, I figured I should start to look at salvaging some of the parts for something new. Just as a last chance, I once again unplugged the processor and juggled the wires and suddenly, it works like a charm!! As with most thing, the threat of imminent destruction got it moving!

Anyway, in honour of it's miraculous recovery, I have fixed up my blog posts and reinserted the graphics Google lost for me. The posts can be found at:

1. Overview of the sensor network
2. Indoor Outdoor temp display
3. Xbee -Gumstix hardware
4. Gumstix-Arduino software

This project is pretty old now and obviously could be done much more easily with newer models of Arduino like the Yun, but it does show some good basics on getting Zigbee and PHP and Arduino all working together. Apparently, too, it is capable of great longevity!

RFID Facebook Updater

I have an RFID reader I bought from www.sparkfun.com and 5 credit card style RFID cards. The reader is hooked up to my Gumstix small PC via serial.

I have two PHP scripts running on the Gumstix. One continuously monitors the RFID reader to see if there has been a card read and it writes that value to a file. The other script is the actual Facebook application that picks up the RFID tag value and lines it up with statuses I have assigned the different cards.

Anyway, very cool to learn how to use RFID and write a very simple Facebook application. In a broader application, this does show that you can "hardware-enable" Facebook so that you could have statuses, new stories, messages generated by a variety of different "real-world" events. This could be a home alarm system or just your plants saying they need to be watered.

While it is possible to generate these kinds of messages through other means (email, SMS etc), Facebook offers a reasonably comprehensive framework for authentication & messaging and a more-or-less documented API.

Here is a shot of the updater & my Gumstix:


And here is a diagram:


I have pretty much stopped work on this as my Arduino-based stuff has come back to the fore front. Some of the things I would like to do with this are:

• Have the status messages stored in a SQL database so they can be updated more easily (currently they are hardcoded into the PHP script for the FB application).
• Have a "remote reader" with an Arduino & an Xbee radio so your status can be updated anywhere in the house.
• Think about how to scale this up so multiple people could use the application. How would it be hosted, how to architect the reader (Arduino with Xport Ethernet, maybe?). Would there be a demand for a Facebook "hardware add-on"?