Using the Texas eZ430 Watch with the .NET Micro Framework

Some time back I got a Texas Instruments EZ430-Chronos watch. One of my better investments. For only fifty dollars you get an LCD watch which you can program. What’s more, it contains a whole bunch of sensors and can communicate with a host device over a wireless link. Around the same time I got a ChipworkX board from GHI Electronics.

So, one lunch hour I decided to try and make them work together. It turns out to be very easy. The watch has a wireless connector (you can just see the PCB at the top of the picture) that appears as a USB serial port to whatever you plug it into. Since the ChipworkX board has USB hosting and serial port support it was an easy matter to get the two talking. A bit of searching and I found the accelerometer protocol for the watch, and away we went.

If you are interested, I’ve created a Watch class that abstracts the watch behind an object that will fire off events when the watch delivers new accelerometer readings. You can find a sample .NET Micro Framework project here.

Fez Micro Robot Bottom

If you are having bother positioning the support posts to hold your Fez Mini robot together you might find the above picture useful.  The PDF gives lots of good detail about how to fit the motors to the battery tray, but lining up the unit with the right screw holes on the base is a bit tricky. I think mine is right, at least the wheels seem straight enough for me. The back of the robot is at the bottom of the above picture.

Oh, and you don’t have to fit the line detectors where I have (just outside each wheel). This is part of an experiment I’m doing to find out how well grey scale line following can be made to work.

Using the FEZ Line Sensors

The Fez reflective sensors let your robot detect what it is running on. You can use them to create line following robots. They are surprisingly sensitive. You can connect them to an analogue port on your Robot Controller. The most important aspect of these devices is that the line you print must be a “proper” black. This means a printout from a Laser Printer, and not the output from an inkjet. For some reason inks are not detected, but the black produced by a laser printer works a treat.

Clearing out your FEZ

I managed (I’m not entirely proud of this) to get my lovely FEZ Micro into a bit of a pickle.  I think I set some pins how they shouldn’t be. The result was that Visual Studio got stuck at “Preparing to Deploy Assemblies to Device” and never got past this. If I tried to use MFDeploy to ping the device it didn’t work. Things looked bad.

Turns out that it is fixable though. The FEZ is a dual personality device. Normally it is a Micro Framework device that accepts programs and runs them. However, it also has a mode where it accepts updates to the internal firmware. TinyClr call this the “’Firmware Updater”. I call it my “Get out of Jail Free Card”.

There is a very useful video from the Fez folks that describes this mode and how to activate it.  First thing you do is watch the video:

Once you have watched the video, installed Terra Term and got the device on the end of the terminal to talk to the terminal program you are ready to clear the memory. You don’t actually want to install any new firmware (so don’t do any of the XModem stuff), you just want to get rid of that nasty Micro Framework program that is stuck in your device. You can do this using the Bootloader program, which is described in Chapter 5 of this guide:

http://www.ghielectronics.com/downloads/USBizi/USBizi%20User%20Manual.pdf

The command you want to use is D.  Just press D and then Y to confirm the erase. You can now exit from Terra Term, reset the device and everything in the garden will be lovely again.

If your PC complains that it can’t find the USB drivers for the FEZ you can find them in the installation directory on your PC once you have installed the FEZ SDK.

I must stress that it is very unlikely that your FEZ will get stuck. I did to something really stupid to break mine, but it is nice to know there is a way back if it does.

Micro Framework Version 4.0

Version 4.0 of the .NET Micro Framework was released in November 2009 and builds nicely on the earlier releases. Since the Micro Framework is now released under an Open Source license you can get hold of an entire porting kit to allow you to run the system on any platform, and you can also get hold of most of the source of the program.

It is great to see the system developing in this way. Over the next few weeks I’m going to be posting some .NET projects, starting with some fun and games with the new FEZ devices from TinyCLR.