Minutes of the PARTS meeting on September 6th, 2003
President Pete Skeggs opened the meeting by announcing that all members should have gotten an email announcement recently from a new PARTS members-only email list. This list has been created to provide a means of sending announcements that would not concern subscribers of the Yahoo PARTS list. Any members who did not receive Petes email announcement should contact club secretary, Doug Arnold.
Pete reminded attendees that elections for PARTS officer positions will be held at the November meeting. In an effort to encourage members to give serious consideration to running for office, the three officers who were present (Pete Skeggs, President; Warren Leach, Vice-president; Doug Arnold, Secretary) announced that they do not intend to run for re-election. Except for the months that lead up to PDXBOT, all three officers reported that they spend 10 hours per month on club activities.
A discussion of possible future directions for PARTS followed. Pete said that the current executive team had discussed a couple of scenarios. One involved keeping things pretty much as they were now, with one major robotics activity each year. A second possibility was to focus more on robotics education, with outreach to school groups interested in learning about robotics.
Someone suggested two levels of membership: one for students/beginners, and another for those with more experience.
Club dues were briefly discussed; it was generally agreed that having dues encourages more active participation and could provide discounts for activities.
Someone suggested that PARTS provide day-long seminars about robotics. Pete responded that he would prefer to leave this type of activity up to Saturday Academy or vendors of hardware products, especially since we have not had much success lately getting members to participate at local community events such as the Beaverton Summerfest and the Japan Festival.
Pete conducted two informal polls of members. A majority of the members present indicated that they would be willing to participate at some level in at least one activity per year besides PDXBOT. A majority of members also indicated that they would be willing to pay club dues to offset the costs of printed materials that promote the club. It was suggested that all of the current member benefits, such as the member discounts on purchases from Parallax and OReilly, be posted on the club website. Pete encouraged members who have ideas for additional PARTS member benefits to send their suggestions to email@example.com.
Pete announced that the topic for the days educational session was a discussion of the relative merits of different microprocessor families. Monty Goodson led the session dealing with the Atmel AVR family of processors. Monty reported that his observations were the result of his use of the ATmega8 AVR chip. The AVR family is a collection of 8-bit RISC processors with varying on-chip capabilities. The line has been optimized for running applications written in C, and has a compact and efficient instruction set. The processor has three memory pointers, making C code easy to run. There are 32 general purpose registers, and the chip supports both 16-bit and 32-bit arithmetic operations. The AVR family supports a rather large RISC set, which means that migration from one processor to another is fairly easy. All of the AVR processors are in-system programmable, and can program their own FLASH memory. The boot loader memory is protectable. On-chip debug capability means you can watch the operation of the chip while developing your code. Schmitt triggering is provided on all inputs, greatly simplifying sensing of mechanical switches. Monty said there are about a dozen different ways of generating PWM signals with the AVR family.
The Atmel STK500 development system is available for about $80, and includes a built-in ISP programmer. Sockets on the board can accommodate most of the AVR family chips. A separate programming cable is available for about $30, and the AVRStudio development software is available free from Atmel. Monty showed the Atmel Butterfly, a demonstration board with a built-in LCD display, clock, speaker and temperature sensor. There are several C compilers for the AVR family. GCC is free, and the standard version of the CodeVision C compiler costs about $150. Imagecraft and IAR are other vendors with C compilers. Monty said that BASIC, Pascal, and FORTH compilers are also available. Monty suggested www.avrfreaks.org and www.atmel.com as web site resources. Two Yahoogroups (avrchat and avrclub) also can provide support.
Warren Leach provided an overview of the Motorola 68HC11 processor. This chip was based on the 6800 processor, and was the result of a General Motors request to Motorola for an engine control processor. Members of the 68HC11 family all use an 8 mHz crystal, which is divided several times to provide a system clock. The fastest instructions take a minimum of two clock cycles and execute in 1 microsecond. Warren reported that the chip has been around so long that there are many development environments. The HC11 has a simple bootloader scheme in which the first 255 bytes sent on the serial port are loaded into memory; bootloaders less than 255 bytes long must be padded to exactly 255 bytes. There are five ports, but only three ports are available if the processor is running in extended mode. There is limited RAM and ROM on board, so additional memory is almost a necessity. As you might expect from an engine control processor, there are multiple timers available, and the resolution of 500 nanoseconds is sufficient for robotics tasks. Interrupts can be triggered on rising or level or falling edges of signals. The 68HC12 processor is the successor to the older are model; this new processor offers a 20-bit address space, and all instructions execute in a single cycle (including a hardware multiply instruction).
Karl Lunt and Kevin Ross both offer boards and software for would-be 68HC11 (12) developers. The assembly language is relatively straightforward, and the ports are simply memory addresses.
Steven Minichiello followed Warrens presentation with some information about the Motorola 68HC1x family. He said that these processors are known in the industry as being fairly "high-end" devices, and they carry a somewhat higher price tag than competing chips. The new Motorola "HCS" series processors are 100% compatible with the HC11 and HC12 families, but offer higher integration and performance. Steven said that there is abundant code support for these families because they have been around forever. He said that he considers the development system to be extremely important; the Motorola system has a built-in emulator.
Steven gave a few highlights of the new HCS12 family. These are 16-bit processors with up to 8Kbytes of RAM, up to 2Kbytes of EEPROM, and up to 256Kbytes of FLASH memory built-in. The chips use a 16 mHz clock, but a PLL multiplies the clock frequency upward. The chips will support up to 512K of external RAM, and have two serial ports, three SPI interfaces, an I2C bus, five CAN bus interfaces, 10-bit AtoD conversion, and seven PWM outputs. Steven suggested that processor selection be given a lot of thought before a project is begun.
Pete Skeggs finished up the review of processor families by discussing the Microchip PIC family of processors. Pete said that these chips are very popular, partly because there is a lot of information (books, web resources) available for folks who want to use PICs. The PIC processors are pretty self-contained, with lots of hardware capabilities built-in. Pete reported that the PICs are not as fast as the AVR series, but they are sufficiently fast for most robotics projects. Pete said that there is a free Integrated Development Environment available and plenty of good (although expensive) commercial compilers for BASIC, C, and JAL. Pete said that support libraries make use of external hardware pretty painless (especially with the CCS C compiler).
Some negatives about the PIC chip family is the bizarre assembler language (if youre not using a compiled language), insufficient on-chip RAM, the lack of a built-in bootloader, and poor support for math functions. Pete suggested that robot builders interested in using PIC-based products consider the OOPIC, the DIOS products from Kronos Robotics, the Brainstem from Acroname, and the various BS2 products from Parallax. Other interesting PIC-based products include the Cypress "system on a chip", and the Signal 8051 equivalent with configurable pin assignments.
Following the presentations about these various processor families, it was suggested that PARTS have a "lending library" of development boards, chips, and books. Brad Lewis volunteered to coordinate this project. PARTS members who have unused or no longer needed items to contribute should contact Brad via email: firstname.lastname@example.org.
The Show and Tell portion of the meeting began with Brad Lewis, who reported that for about $75 he got a module from EDTP that connects a microcontroller to the web. He can now control his telerobot with a web browser. More details are available on Brads website.
James Davis said that he is looking for recommendations of 16-bit microprocessors, and would like some information about using the Scott Edwards Electronics SSC serial servo controller board.
John Gregory brought in a robot that he built to pull cable in the crawl space below his house. He used _-scale RC servos as wheel motors, a video camera, and Linx Tech RF modules to remotely control the robot. To power his robot, John used a 3000 mAh 2/3 "C" battery commonly used in electric model airplanes. John also showed a robot-in-process that he intends to use for line following and maze solving. He has installed encoders on his wheels and is using Hamamatsu IR sensors.
Tim Weaver reported that he has designed an all-new PCB for LandShark. This new design will use fifteen IR sensors so LandShark will always know where its opponent is. Tim said that he determined why he was burning out his motor driver chips: he switched to larger-gauge wire for his motors, and the lower resistance allowed additional power to flow, thus burning out the driver chips. Tims new design toggles the Enable lines to turn the motor drivers on and off.
Monty Goodson reported that there has been a lot of activity on the Yahoo megaBitty group dedicated to using his micro-sumo controller board. Monty recently built a programming fixture using pogo pins. He is now selling assembled and tested megaBitty boards with a bootloader for $45. Monty showed the magnetic fields of a disk drive motor armature with some magnetic display film he bought from Wondermagnet. He also recommends NWMagnets as a local source of high-strength magnets.
Dan Gates urged RoboMaxx competitors to visit the Southern Oregon Robotics website to register robots in advance. Robots will not be weighed during registration at RoboMaxx; instead, the winners of each match will be weighed. This will speed registration. RoboMaxx will be October 11-12, with battle bots events on the first day, and sumo and maze competitions on the second day. Dan showed a line following development platform outfitted with a CMU Cam. He showed his articulated robot legs with six degrees of freedom; these are intended for a walking robot. Dans legs use the Hi-Tec HS645 servos. Dan will supply the legs for the prototype walking robot that New Micros is building; their controller board will drive up to 26 servos. Dan is building a walking robot, and plans to use R/C helicopter stabilization gyros for balance. Dan reported that Little Johnny was melted during filming of the new "I, Robot" movie starring Will Smith. Apparently Little Johnny was positioned too close to Klieg lights, and was melted beyond repair. Dan will write an article for the new robotics magazine, Servo, that is being spun off from Nuts and Volts magazine.
Larry Geib brought in ChickenBot, his first walking robot. ChickenBot is controlled by a Parallax BASIC Stamp, and uses only two servos. Larry also reported that he may be able to produce a repeatable gray value for next years line following event by using a larger checkerboard pattern.
Daryl Sandberg brought in a power sunroof assembly and remote control rear view mirror assembly for someone to turn into robotics projects. He showed his new mini-sumo challenger to Solo and LandShark; this robot will be more intelligent, and faster, not just stronger. It will use wheels 30 mm in diameter with treads 37 mm wide. He will keep the height under 45 mm in order to keep the front slope less than about 10 to 12 degrees.
The next PARTS meeting will be Saturday, October 4th at 10:30 am in PCAT 28.