Spent a good deal of time on Saturday working with the Base Station and my collection of sensors. I’ve managed to decipher enough information from both the Serial and ZigBee side of things to come up with a workable solution for my needs.
I picked up an Atmel RZUSBSTICK (Available on Mouser and elsewhere) based upon information from Josh Wright’s published ZigBee documentation. His KillerBee framework was invaluable in my effort to understand the Home Heartbeat’s wireless communication. I’ve ordered a copy of Hacking Exposed Wireless, Second Edition in order to delve a bit deeper into this realm, as it’s quite interesting. Josh’s Toorcon slides are a good read as well if you’re interested in this sort of thing. The HHB’s usage of ZigBee is very basic, and took surprisingly little time to decipher once I had the proper tools to monitor the traffic.
I’ve explored three primary avenues for modding the original HHB base station for my needs. The first option involves developing new firmware for the HHB. Since the HHB base station is based upon an Atmel AtMEGA128L, this would certainly be technically possible. If I had more time at my disposal I may have selected this option; starting with an assembly dump of the existing binary image would provide a pretty good start.
The second option involves developing an intermediate device which acts like a Home Heartbeat key but which provides an interface to additional functionality. The device would utilize a simple ZigBee radio to speak with the base station. The base station/key protocol is quite straightforward. This approach has several advantages: the base station basically remains in its unadulterated form, and the new device could provide any number of additional features (internet connectivity for notifications, etc). The Chibi Wireless Board from the fine folks at FreakLabs would be an ideal platform for this effort, as it provides the necessary wireless hardware, is Arduino compatible, has a proven track record (Safecast.org hardware is based upon this board), and is cheap as well – $30 USD for the bare board. I will probably pursue this option in the long term, as it would be an interesting project to work on. I’ve already ordered a couple of Chibi boards with enclosures to experiment with. Check out the site’s wiki as well – Akiba does some amazing work, and the best way to support his efforts are by buying stuff from his store.
The final (and simplest) option involves interacting directly with the base station as a serial client. There is enough information available via serial to interact with the sensors and report on activity. I’ll be basing my solution on this approach using the Arduino Ethernet board; stay tuned for build details.
Throughout all of my digging I’ve come to the conclusion that the HomeHeartbeat device and sensors have a lot of hacking potential. As they are all built around the Atmel ATMega microcontroller (ATMega128L and ATMega64L), it should be possible to build out some simple tools to take advantage of all of the available Arduino libraries to build some pretty cool devices. The HomeKey in particular would be fun to hack, with its built-in backlit graphical LCD screen, thumbwheel, and ZigBee radio. I’ll spend some time tomorrow documenting my findings with the HomeHeartbeat sensors; lots of pictures and technical information to share!
Keep the comments coming – I’d love to hear more about how people are using this hardware as well as any crazy ideas that you may have for hacking the hardware. Please respond via comments rather than emailing me directly so that the discussion is not just limited to two people. I’m hearing a lot of duplicate information and requests from people via email. It’s been really cool to see my site traffic picking up over the last couple of weeks!