Wednesday, July 6, 2011

Control a robot with a watch

Some six months ago Texas Instruments announced the Evalbot, a development platform for their Stellaris ARM Cortex-M3 microcontrollers in the shape of a little robot. It took me a while to get hold of one, but now I have one driving happily around in my living room. It is actually a pretty neat and cleverly engineered kit that you have to assemble yourself. Most parts are made out of PCB material – the two wheels for instance are each made of three disks and a rubber ring – the rest are mainly nuts & bolts. Two little motors with gears drive the wheels and everything is powered from three AA batteries.

The Evalbot is not a gadget; it is a powerful development board with wheels. In the center off the disk-shaped board sits an LM3S9B92 ARM Cortex-M3 controller (256 KB flash, 96 KB RAM and more peripherals than you will probably ever need) assisted by a tiny 96 x 16 blue OLED display, 6 push-buttons (including the on/reset and the off buttons), an Ethernet connector, a USB host port, a USB device port, a USB debugger/programmer port (ICDI), a micro-SD card connector, a speaker, power supply, JTAG, two LEDs and probably more that I am overlooking now; and two motor drivers. Thanks to the battery holders (with batteries) on the bottom of the board the whole thing is pretty heavy and the rubber “tires” prevent sliding it off your desk when you hook the board up to a computer with a USB cable that wants to unwind the wrong way around.

A special wireless expansion port is available too on which you can plug a CC1101EM sub-1 GHz transceiver, which will get you an 868 or 915 MHz radio link. The James Bond part of this setup is a third kit from TI, the eZ430-Chronos based on the CC430F6137 sub-1 GHz RF SoC. This is a combination of a biggish but stylish black watch with a large character display and a USB access point for your PC. Once connected you can control your PC with the watch, although it takes some exercise to do it properly. But... you can also use the watch to control the Evalbot! An integrated accelerometer lets you influence the driving direction of the robot by tilting and rotating the watch. Cool huh? The watch in itself is actually a dev kit and you can reprogram it with your own application.

Programming the dev kits is done with Code Composer Studio 4, the Eclipse-based dev environment from TI. A license file is included with the Evalbot kit, but what exactly this enables is not clear to me. I did read something somewhere about code sizes & limits, but I forgot where. Anyway, all the source code for the Chronos controlled Evalbot is available, it compiles without warnings and errors and programs fine. This really is a fine (but strange) development kit.

1 comment:

  1. That is awsome, and much more intuitive than the other Chronos/robot projects I've seen who usually takes on the chronos->computer->robot path instead. I bet TI is very happy to have this project for showcasing two of they're most awsome eval kits ;)

    Just got the chronos myself, I want the evalbot badly. I'm sad I got the 433MHz version now that I realize (almost) all the accessories are 868/915MHz.