The Texas Instruments eZ430 Chronos is a cool gadget. It has bidirectional radio communication, and a whole bunch of sensors: temperature, pressure, acceleration.
In fact, it is a development kit for the MSP 430 (a low-power microcontroller), that TI packaged as a watch (pure genius!), and delivered with plenty of tools. Its firmware can be modified to implement new features into the watch.
Even without developing anything on the watch, it is a terrific toy:
- the watch alone is pretty cool --and has the TI logo ;-),
- the default features allow for a wide range of cool experimentations and developments around it.
The RF communication has a quite short range, and quite low consumption. It is not Bluetooth, but SimpliciTI[TM] or BlueRobin[TM].
Pretty much documentation about the watch (sample code, specifications, schematics) can be found on the Web. Google is your friend.
Watch to PC
The watch comes along with an access point (i.e. the peer device the watch can talk to) in the form of a dongle, incorporating a TI chip that can, on one side, talk to the watch via RF, and on the other side, talk to the PC via an USB slave interface.
When the access point is plugged into a PC, a PC application provided by TI can exploit it to communicate with the watch: graph sensors, set the watch time, calibrate sensors, send fitness data. The nice thing is that TI wrote it in a scripting language (venerable Tcl/Tk) to run on multiple OS-es.
It is very easy to write your own PC application, as shown by some examples written in Python. There are numerous such examples that can be found on the web.
Watch to Arduino
What about using an Arduino instead of a PC? You could make completely pocket-sized projects!
Surprisingly, I could not find any clue about it on the web.
I evaluated several USB host libraries, and finally found the right application source code to get started (ACM on CDC, for modem, by Circuits@Home, http://www.circuitsathome.com; Oleg, thanks for the library, examples, and for the help!).
It finally works, it's very simple, and that's what I'm covering with the present post.
Just basic Arduino knowledge is required. However, this post is not an Arduino tutorial.
Enough said, let's get to the point!
Step 1: Needed Stuff
You can purchase the TI eZ430 Chronos watch from several resellers (e.g. Mouser, Farnell, or Amazon). It will come along with:
- software and doc on a CDROM,
- an USB dongle that is an RF access point,
- an USB dongle to reprogram the watch, (we won't use it here),
- a screwdriver to open the watch (we won't use it either * )
Any more or less standard Arduino will do, and the most important thing is to have USB host capability.
For this, the following configurations are among the possible ones:
Arduino (mine is Duemilanove) and an USB host shield (mine is from Circuits@Home)
- or -
- Arduino Mega ADK (important: must be ADK variant! it has USB host on board)