A forum member asks: “I noticed that recent Nuts & Volts articles are almost exclusively for SX, instead of the traditional BS2 codes”.
I was recently browsing the Parallax forums when I came across the above interesting article started by one of our support forum members. It got me thinking about a well known song lyric made popular by the pop group Simple Minds, “Don’t you forget about me”! It also got me thinking about the SX chip and how versatile, powerful and flexible this little chip is. While Parallax has created the Propeller Chip and we focus some of our attention on this incredible new chip, it’s always refreshing to be reminded about just how wonderful the SX chip is and all its functions.
A response from Jon Williams - Author (Servo/Nuts & Volts), Forums Contributor, Entrepreneur (EFX-TEK):
I will continue to write about the SX because, frankly, there's not enough material on it now; the BASIC Stamp has been around forever and there is a TON of written material for it (some by me), and the Propeller is the new golden child so it's going to get a lot of attention from Parallax. The fact is that the SX is a rockin' little chip, especially with SX/B for folks like me that don't have the patience for 100% assembly language. The fact is that I've become a better assembly programmer because I can see the output from SX/B, and this was the original intent for that compiler. SX/B continues to get better every day which allows us users to get more out of the SX.
No, I'm not saying that the SX and SX/B are perfect, but they do work very well for me. Truthfully, I use the SX every day. I like it, my customers like it, and until the general Parallax user base has the same comfort with the SX as they do with the BASIC Stamp I think I should keep the focus of my articles on the SX.
Just so you know that my use of the SX goes beyond my columns, these are the commercial products I've designed/coded with the SX and SX/B
EFX-TEK AP-8 (ISD audio player; hardware design by JB, coded by JW and JB)
- EFX-TEK DC-16 (digital output expander)
- EFX-TEK RC-4 (relay controller)
- EFX-TEK FC-4 (lamp controller/fader)
- three additional EFX-TEK projects in design now
- solenoid controller (part of a hand-held compressor created by an airbrush make-up company)
- LanC controller for video cameras
- Pan/Tilt head controller
- digital candle (for huge SoCal amusement park)
- DMX lighting controller (for same HUGE amusement park)
And yes, I'm always open to ideas.
Jon Williams
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MyDanceBot and ViewPort Software by Hanno Sander (MyDanceBot.com)
MyDanceBot is an autonomous robot that balances naturally, yet precisely on common surfaces.
How do hobbyists or educators go about building a robot which does not need legs, platforms, flat surfaces or 4 wheels to stay upright? Combine the power and multiple functionality of the Propeller Chip with the vast capabilities Viewport 4.0 and the dream becomes a reality. One such project was created by Hanno Sander, builder of sophisticated yet affordable robots including his favorite, the DanceBot.
Today’s robots are difficult to program, inflexible to changes, and move robotically. When Hanno started experimenting with balancing robots he started thinking about making robots more fun.
Goal: A Robot that is fun and easy to use: a dance partner.
Vision: Take DanceBots to a party where they dance intuitively with strangers. First robots that don’t need to be programmed- just dance with them to have fun. They keep a set distance while continually facing their partner and look like they’re enjoying themselves.
Challenges:
- Maneuverable platform: turn on a dime, Move organically: not rigid like car
- Can be programmed to move precisely: needs to move at set speed
- Robust- should dance on common surfaces: carpet, wood, grass, slopes, different lighting
- Affordable and autonomous
Solution:
- Balancing robot with 2 independent motors
- 2 Fuzzy PID controllers to stay balanced at a given speed
- Kalman Filter with Gyro and Accelerometer to measure tilt
- Parallax Propeller and ViewPort
Hanno explains in his own words how all this was possible:
After watching friends demonstrate their Roomba Robotic Vacuum cleaners at a party, I wondered if I could teach my balancing robot to dance. Not just with me, but with anyone in any environment. I wanted to build a robot that could dance with people and seem almost human.
I believe balancing robots make a great platform for mobile robots. They are highly maneuverable, have great traction, and move more smoothly and naturally than other designs. They can turn on a dime, navigate precisely with dead reckoning and are a pleasure to watch while they keep their balance. Unfortunately, building a robot that balances and maintains position robustly in any environment is not easy.
The first lesson I learned was that unlike the inverted pendulum problem, a true balancing robot requires two control loops. One control loop to keep the robot from falling and another to keep the robot from losing its position. This combination also lets you move it programmatically. A significant milestone for building a balancing robot involves taking a simple step- accelerate to a set speed, travel, and then decelerate to a stop. DanceBot uses what’s known as a “hybrid fuzzy logic cascading PID controller” to precisely carry out this and other advanced maneuvers. In the algorithm the inputs to the PID controllers are first processed by a fuzzy logic engine to make the control algorithm more robust and easier to tune. The PID controllers, which correct the error between a measured variable and its setpoint by calculating a corrective action, are arranged in a cascade with the output of one used as the setpoint in the second.
Secondly, while it’s possible to determine tilt by optically measuring the distance to the floor, this technique isn’t robust. DanceBot measures rate of turn using a ceramic gyroscope and integrates this signal to calculate tilt. Fusing the calculated tilt value with measurements from an accelerometer with a Kalman filter yields an accurate tilt reading with no drift- in any environment. This combination gives DanceBot perfect balance for any amount of time.
Once my robot could balance I wanted to give it a purpose. I needed an algorithm that would provide the target speed and heading to autonomously drive the robot. After experimenting with remote control and line following I developed a computer vision module to dance with people. Adding this module was straightforward because I buillt DanceBot using the Parallax Propeller and the ViewPort Development Studio. The Propeller combines 8 processors running at 80MHz in a low cost chip. ViewPort runs in one of the 8 processors to continually stream DanceBot’s state to a PC-based graph and control program. Since the balancing algorithm runs in 2 processors DanceBot had ample processing power to digitize video into memory and continuously apply simple vision filters to determine the location of its partner in real time.
Debug Propeller Programs with ViewPort
ViewPort is widely considered one of the best tools for building advanced projects with the Propeller including building sophisticated, yet affordable robots.
Hanno Sander developed ViewPort to debug and tune his balancing robot. He chose the Propeller because its 8 processors (cogs) allowed him to break his complex project into simple modules that could be developed and tested independently. By dedicating one cog to ViewPort, Hanno could monitor and control his robot from the PC. ViewPort uses views to organize data on screen. Simulated instruments like an oscilloscope, logic state analyzer, and spectrum analyzer allow him to measure and analyze his system. This has helped him debug SPI communication problems, tune PID loop constants, and develop a vision algorithm to make his robot dance with others. The new release makes it easy to integrate any Propeller program with ViewPort. A single line of code at the start of a program starts a cog which continuously communicates with the PC to share variables and process commands- all configuration can be done in the customizable graphic interface. Optional ViewPort objects allow sampling the IO port at up to 80MSps, digitizing and processing video and calculating with fuzzy logic.
A free 30 day download which includes tutorials and a 60 page manual is available here: http://mydancebot.com/viewport
To learn to use the ViewPort software with your Propeller Education Kit, download this new Lab:
ViewPort App
The
OpenStompTM Coyote-1 is an open source audio effects processor built for guitar players. With the Coyote-1 users can develop custom audio effects in software (like distortion, echo, chorus etc.), mix multiple effects to build "patches", and exchange those effects and patches with the OpenStomp community.
At the heart of the Coyote-1 is one the coolest, most innovative, and just plain knock-your-socks-off fun microprocessors to come along in a decade; the Propeller from Parallax. The Propeller contains 8 independent processor cores running simultaneously at 80MHz with a unique architecture supporting a high-level byte coded language called "Spin", and a low-level assembly language with an amazingly versatile instruction set.
The Propeller development tools are all free, and the Propeller architecture allows users to develop firmware with nothing more than a simple USB cable. Its revolutionary architecture allows the Propeller to generate video in software by adding just three external resistors, so the Coyote-1 includes a video out port which can be used by developers for debugging or adapted to implement things like graphical tuners, spectrum analyzers, oscilloscopes, or light shows.
September 4, 2008 marked the conclusion of Parallax Inc’s 20 year anniversary celebration. Many prizes, products and specials were given away throughout the year to celebrate this incredible achievement. Since 1987 Parallax has been making products that allow companies and individuals alike to create and build incredible products and projects. Parallax has always based its ideas and products on a simple philosophy. Build products that create solutions and are built of the highest possible quality. From the BASIC Stamp microcontroller to the Propeller chip, we are proud that our customers have enjoyed our products for over 20 years and continue to support our business. Here’s to another 20+ years of fun and excitement together!
Beginning in this edition we will begin spotlighting some of our many trusted and valuable distributors of Parallax products. It’s our goal to provide our customers with the best quality, lowest cost products possible. This year our goal is to expand our product offerings thru our distributor channel to add convenience and provide lower product and shipping costs to our customers. We encourage all our customers to consider using our distribution partners when considering the purchase of Parallax product. Look for more distributors in upcoming editions or visit our website at
http://www.parallax.com/Company/LocateaDistributor/tabid/69/Default.aspx
http://www.jameco.com - With thousands and thousands of products to choose from, finding the right product can be difficult, as well as searching for specifications and finding similar products for comparison. Jameco’s site has one of the most powerful and sophisticated search engines in the electronic components industry. We’ve designed it to be flexible and search the way you want to search. The Jameco search design features four levels on your way to finding the products you need.
http://se.mouser.com/ - Mouser Electronics, Inc. is an electronic component distributor, focused on the rapid introduction of new products and technologies to electronic design engineers. Mouser.com features over a million products online from more than 366 manufacturers. Mouser’s 2,128+ page catalog is published every 90 days, providing designers with up-to-date data on the components now available for the next generation of electronic devices. Mouser ships globally to over 280,000 customers in 170 countries from its 432,000 sq. ft. state-of-the-art facility in Mansfield, Texas.
Meet Mark. Mark works in our warehouse kitting dept. You can often find Mark running around the building putting together all of your favorite kits! We ask Mark to tell us a little about himself. Here’s what he had to say.