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Evalbot Chronos USB Control

Evalbot (EKB-UCOS3-EVM from Texas Instruments) is a simple, jet fun robotic development platform for ARM® Cortex™-M3 Stellaris (LM3S9B92) microcontroller. Another great tool from TI is a MSP430 Chronos a programmable sport watch with radio-enabled MSP430 microcontroller (CC430F6137). Evalbot has a headers for TI's standard radio modules. You can plug the CC1101EMK module and use sample code from StellarisWARE (StellarisWare\boards\ek-evalbot\chronos_drive\) to drive your Evalbot remotely.

Operation in such configuration can be seen on the following video (Property of Elektor International Media):


Evalbot also has a USB OTG functionality. I was curious if is it possible to use a CC1101 USB dongle shipped with Chronos to drive Evalbot. What I found was that the dongle is just a simple CDC Class device. I was able to write a very simple CDC Host driver and receive packets from Chronos. Chronos is using stock unmodified firmware. Simply start accelerometer mode just like in the TI Control Center demo.

Wave playback

There is even more! Evalbot has an build in micro SD card slot and audio coded with small speaker. The V2 binaries allow to play wave files.

  • Wav file format: MONO 16 bit 11025 [Hz]
  • SD card file system: Fat
  • File naming: 3 digit hex: 000.wav, 001.wav 002.wav, …, 00A.wav, 010.wav …

Files are being played in a loop. You can play next file using SW2 button on Evalbot, or Chronos' # button in acc mode. The * button selects next file without playing.


You can flash following binaries using LM Flash Programmer.

Source code is currently not available.


The effect of the program can be seen on the following video:


After powering the device on USB dongle is enumerated automatically. The radio link is inactive until user press SW 1 button. Pressing this button toggles SimpliciTI link.

The Chronos uses stock software in accelerometer mode. Tilting watch forward makes robot drive forward. Tilting sideways causes robot to turn. To stop the robot simply move your hand upwards.

  • Yellow LED on the Ethernet socket signals successful enumeration of USB device.
  • Orange LED on the Ethernet socket signals SipliciTI packets reception.

Future development perspective

This project can be extended. I doubt I will return into it as my design assumptions were fulfilled. Some of the possibilities are:

  1. Creating Chronos-specific USB CDC Host driver and publishing source code for it.
  2. Making drive control more fluid (variable speed of wheels during turning)

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projects/evalbotusbdrive.txt · Last modified: 2012/09/01 10:51 by mkucia