Let's say you're the lead engineer on a really nifty projectóthe design of a mechanical spider that walks on water. You're unfazed by the mechanical complexities, because you've got lots of smarts and plenty of relevant experience. You're still troubled, though, because you know this beast is going to need a microcontroller for a brain, and microcontrollers are something you've just never had time to learn about.
Robotic waterspiders, designed by cyberartist Remo Campopiano, use Basic Stamp modules for control. Campopiano receives assistance in building the spiders from the Robotics Art Club of New England, a group of 10-13 year olds.
Maybe you should check out the Basic Stamp, a tiny computer from Parallax, Inc. (Rocklin, CA). It's the heart of several development kits, costing as little as $49, that can teach you about microcontrollers and the kinds of devices they interface to. The Basic Stamp is also capable enough to go into real design projects, as evidenced by successful application to areas ranging from industrial control to rocketry to robotics (including a robotic waterspider). It has even gone into experiments on the space shuttle.
Although the Basic Stamp isn't your only option for low-cost, educational microcontroller development systems, it is by far the most popular. Since the introduction of its first version in 1993, it has gained almost a cult following of avid users. Enthusiast magazines like Circuit Cellar and Nuts & Volts frequently publish articles on different uses for it, and their ads feature add-on products and copycat products galore. Dozens of books detail how to use the Basic Stamp in a wide variety of applications.
So just what is a Basic Stamp? It's a very small and simple computer, built on a circuit board about the size of a postage stamp, that runs programs written in Basic (thus the name). It has either 8 or 16 I/O pins, depending on the model, that you can use to interface to devices such as switches, LEDs, speakers, and potentiometers. By adding a few extra components, you can also connect to solenoids, relays, and other devices that require higher voltage or more current. Available instructional materials explain how to use all of these devices.
Components of the Basic Stamp include an 8-bit microprocessor, a ROM chip that contains a Basic interpreter, and an EEPROM chip that stores the Basic programs you write. You write a Basic program on your PC using the software that comes with a Basic Stamp development kit. You then download the program to a Basic Stamp's EEPROM using your PC's parallel port or serial port. As soon as the program downloads to the EEPROM, it runs automatically. Because the EEPROM is non-volatile, it retains your program when power is off, and you can reprogram the Basic Stamp as many times as you like.
The Basic Stamp finds wide use in research laboratories, where its low cost and ease of use make it suitable for small, one-of-a-kind projects. It's also popular with mechanical engineers, reports Parallax founder Chuck Gracey. "Electrical engineers are often disappointed that it doesn't have more features," Gracey says, "but mechanical engineers just want to get a job done."
A particular appeal of the Basic Stamp to MEs, who are less likely than EEs to have learned about microcontrollers in classes, may well be the instructional books and experimental kits that are available for it. The materials available from Parallax range from simple and general (What's a Microcontroller? and Basic Analog and Digital) to more complex and specific (Robotics!, Earth Measurements, and Industrial Control). Prices for kits, which include books, range from $39 to $119. (You also need the $109 Board of Education development kit.)
The heart of a Basic Stamp is an 8-bit microprocessor. Clock speeds for the processors in the various Basic Stamp models range from 4 MHz to 50 MHz. The simplest Basic Stamp can run programs of about 80 Basic instructions at a rate of roughly 2,000 instructions per second. The most advanced model can handle 600 instructions at 10,000 instructions per second.
If you need bigger programs or faster execution than a Basic Stamp can handle, you can turn to a host of other suppliers for additional capabilities. For example, you can get a Basic compiler for the Microchip PIC processor that's in many models of the Basic Stamp. These compilers turn your Basic programs into native microprocessor machine code before downloading, thus reducing program size and greatly increasing execution speed. They're available from companies such as Code Designer, Basic Micro, and Micro Engineering Labs. You can also get hardware modules that are more powerful than some of the Basic Stamp models. Micromint and Technological Arts, for example, are sources for these.
For microcontroller development kits that are less basic, but still inexpensive and easy to use, you might consider Rabbit Semiconductor. Rabbit kits cost as little as $139 and are based on the Rabbit 2000 processor, a modified version of Zilog's popular Z180. You program the Rabbit 2000 in Dynamic C, a proprietary version of C developed by Rabbit's parent company, Z-World, specifically for embedded control. Together, Rabbit and Z-World provide a wide range of controller hardware, so you can start with a simple system and then move up to a more powerful, but compatible, system if necessary.
Finally, don't overlook mainstream microcontroller manufacturers as a source of instructional material. Some of them offer fairly basic development kits and learning materials, and all of them have a vast range of technical documentation that goes far beyond the basic level. The chip companies also have savvy application engineers that can help solve the tough problems you face. That's their job, and most of them do it well.
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