Portland Area Robotics Society

Regular Meeting Minutes

August 5, 2006, 10:30AM



1.      Presentations:

a.       Mark Medonis %G–%@ demo of code loading on Freescale semiconductor microcontroller

2.      News Reports

a.       Show-and-tell


1. Monty Goodson announced a table-top contest for next months meeting. Implement a line-following robot capable of following a black line on white paper to turn a 90-degree corner. See the Yahoo group for details.



a. Mark Medonis %G–%@ demo of code loading on Freescale S12 16-bit 50Mhz microcontroller

Mark is using a $50 demo board from Freescales website and a USB pod for programming. The USB pod provides debugging capabilities also.

Marks programming is in C-language, using CodeWarrior. A free compiler is available, limited to 32Kb of code size. The compiler supports C, C++, and Embedded C. Code is compiled through the make utility. The debugger is accessible from CodeWarrior also, enabling direct access to memory and code breakpoints.

Versions of the S12 are available with built-in USB or Ethernet.

b.                Larry Geib %G–%@ demo of Parallax Propeller microcontroller.

The Propeller chip costs $25. A downloading interface is needed. Larry is using the Parallax USB interface available for $100. The Propeller has 8 microcontrollers and a central controller and bus interface unit. It includes a 32k RAM. Each cog has a private memory space of 512 words. The Propeller chip runs at 80Mhz. It provides a simple interface for driving PAL or NTSC video devices.

There are 2 ways to program the chip %G–%@ assembly language, and a language that is similar to BASIC. The on-board ROM downloads an interpreter program to each on-chip cog microntroller. Parallax provides a library of demonstration programs and example code on its web site.

Within the IDE, code files can contain schematic symbols to record the circuitry used by the code. The language is like BASIC, but it is somewhat like Python also %G–%@ formatting and indentation are used to define code blocks.

Larrys demo program blinked 2 LEDs, each controlled by a separate cog controller on the Propeller chip.

c.                Monty Goodson %G–%@ demo of Atmel AVR 8-bit programming using the MegaBitty board.

Monty is using the Code Vision AVR C-compiler and IDE. The full version costs $150, but a code-size limited free version is available also. Compilers are available for other C versions and other languages. Others using WinAVR ( a free GCC compiler) have had good experiences.

Monty demonstrated code set-up and programming in CodeVisionAVR. He configured interrupts and PWM through CodeVisions Code Wizard menus. Montys demo program and hardware controlled a DC motor using PWM. The speed is based on a value retrieved from an IR distance sensor. The code also used a sensor to trigger an interrupt routine. The interrupt stops the motor while the sensor is activated.

Monty uses the AVR ISP (about $30) for in-system programming of AVR chips. After initially loading a bootloader program, other programs can be downloaded to the chip using a serial port and a $10 serial port level converter. Monty uses the MegaLoad bootloader (however, setting up the latest version is somewhat complicated; use the older versions if possible).


1.     CodeVision: www.hpinfotech.ro

2.     AVR Studio: www.atmel.com/products/avr

3.     AVR Freaks (user group): www.avrfreaks.com

4.     MegaLoad: www.microsyl.com/megaload/megaload.html

d.                Domnic Casey %G–%@ demo of the Parallax Boe-bot robot

The demo program uses a range sensor, drives servo motors, and toggles LEDs. He passed around the robot and his BASIC code. The entire project uses only components from the Boe Bot kit. The program downloads over a serial port. The code editor is free from Parallax. The kit includes an excellent instruction manual that teaches programming and circuit design. Sensors can be added to the robot using the included solder-less breadboard. The kit sells for about $150.

e.                Jeff Steidl %G–%@ demo of FPGA programming

Jeff is using Spartan3 FPGA chips by Xylinx. Code is written in VHDL. The WebPack from Xylinx provides a code development environment. Jeff is using a $100 Spartan3 demo board.

Using the code editor, you can configure inputs and outputs and automatically generate some code. Jeff demonstrated the implementation of a multiple channel fixed-width PWM controller.

f.                   Paul -- programming of PIC microcontrollers

PIC microcontroller programming is similar to AVR programming. In-circuit programming is possible, provided that the programming lines can be isolated from the rest of the circuit.

Show-and-Tell and News

Larry Geib is working on an 8-survo walker. He hopes to have it completed in time for the Seattle walker competition.

Bob Pearson has been working with Vex kits. He is planning to switch to C programming. Programming is possible in Microchip PIC MPLab.

AVR-based robot using aluminum extrusion framing. Power from automotive window motors. He is planning to implement a vision-based line follower robot on this platform. Members recommended the AVR Cam camera.

Monty Goodson demonstrated speech output on his MegaBitty controller board.

Tim Weaver has started working again on his flying robot chassis. It has two rotors driven directly by 3-phase brushless motors. Tim is using the MegaBitty board for control and 2 independent 10 amp motor drivers. It has two survo-driven fins to provide directional control and stability. The chassis was laser cut by PC Laser Works.

Don Young is working on a OS-X port of the AVR toolchain. See the AVRFreaks website for details. Don also works on art-based robots %G–%@ see digithink.com/embedded

Martin has made further progress on his omni-directional line following robot. Sensors are hooked up and working. He has found some difficulty setting the thresholds on multiple sensors %G–%@ each sensor has different sensitivity.