Super-small and super-smart, new microcontroller development systems are changing the shape of embedded design
Rick Grehan
Miniaturization has created a new twist in the world of embedded design: The development system is also the target system -- you design on the system that you deploy. Your PC becomes the development host and is tethered to the target via a serial cable or a specialized parallel cable.
Four development boards
from Blue Earth Research, Micromint, Parallax, and Z-World are indicative of this trend. Such systems can include as few as two chips plus a few glue components for power-supply regulation and communications.
The Stamp
Parallax's Basic Stamp is currently king of the miniature hill. Two chips -- one serving as the processor, the other acting as the
serial EEPROM -- do it all (not counting the support circuitry). It all fits on a 16-pin single in-line package (SIP), which you plug into a carrier board during development. The board is not much bigger than the 9-V transistor battery that powers the whole thing. A special cable connects the Stamp to your computer's printer port.
You program the Stamp in an admittedly anemic dialect of BASIC. But this becomes understandable when you recognize that you're working with just 256
bytes
of program space and 14
bytes
of variable space.
Parallax has offset the language's limitations, however, with specialized commands. For example, a single Stamp BASIC command can emit a pulse train out of an I/O-port pin (the Stamp has eight of them) with a specified duty cycle.
The Domino Effect
Micromint's Domino-52 comes in a solid epoxy package that looks like an oversize IC (it measures 1.1 by 1.75 inches). Inside is an 80C52 processor with ROM BASIC as well as 32
KB of static RAM (SRAM) and 32 KB of EEPROM (for program storage). A row of 20 pins along the underside provides an 8-bit bidirectional I/O port, a pair of interrupt lines, a serial port, and access to an optional 12-bit, two-channel A/D converter.
As with the Stamp, you program the Domino-52 by plugging it into a carrier board that provides power regulation and communications hardware. Micromint also offers an optional multiwindowed host-based integrated development environment (IDE), called Host52, that serves as an editor/terminal program.
The BASIC dialect understood by the Domino is BASIC52, a reasonably orderly version that's far more robust than the Stamp's BASIC. It supports floating-point, one-dimensional arrays and a kind of rudimentary string handling.
Micro Genius
Compared to the other devices in this review, Z-World's Micro Genius is a Hulk Hogan of capabilities. It uses a Zilog Z180 that runs at 6.144 MHz. The Z180 is a descendant of the venerable Z80 p
rocessor with mutated abilities that include, among other things, addressing for up to 1 MB of memory.
The Micro Genius can support a variety of memory configurations. Its base version comes with 32 KB of SRAM and 32 KB of EPROM. The EPROM is socketed, allowing the system to support up to 512 KB of EPROM or 256 KB of EEPROM.
The base-model Micro Genius also includes an RS-232 port (used for communications with the host) and a 555 timer IC configured as an analog input channel for measuring external resistance. Without consuming any additional board space, an upgraded version also has a real-time clock and an RS-485 circuit (for building "networks" of Micro Geniuses).
You program the Micro Genius with Z-World's Dynamic C, which includes a full-blown IDE that includes an editor, a C compiler, and a debugger. The IDE lets you open watch windows, evaluate expressions, single-step through the executing program, and even examine CPU registers.
Dynamic C is an extended version of C. For examp
le, it supports
costatements
, types of constructs that allow cooperative multithreading. The number of routines and libraries provided is stunning; the package even includes two real-time kernels.
Exploration
Blue Earth Research's Xplor connects to your PC via the serial port. Programming the Xplor is simply a matter of firing up a communications program and entering BASIC code. Once you've entered and debugged your program, that's all there is to it; the code is automatically saved in the Xplor's on-board 4-KB EEPROM. Turn off the Xplor, install it wherever it needs to be, and the next time power is applied, the Xplor executes your program.
I tested the lowest member of the Xplor family tree: the Xplor-32. Its rudimentary I/O hardware consists of 12 digital I/O lines.
The capabilities of the Xplor's version of BASIC fall somewhere between the Stamp's and the Domino-52's. The Xplor's BASIC understands integers only and has no concept of strings or arrays. It
provides a set of commands for controlling program flow, as well as special functions for reading the system's built-in A/D converter (functions that are not available on the Xplor-32) and returning the frequency of a wave form at one of the input pins.
Little Is Big
If you do embedded design, these little systems mean big savings. You don't have to spend money on in-circuit emulators, ROM emulators, EPROM burners, and so forth. All you need is a relatively modest PC and some extra space on your desk.
PRODUCT INFORMATION
Basic Stamp
With carrier board $54
Parallax, Inc.
Rocklin, CA
(916) 624-8333; fax (916) 624-8003
info@parallaxinc.com
Domino-52
Without A/D converter $79
With A/D converter, development
board, and software $198
Micromint
Vernon, CT
(203) 871-6170; fax (203) 872-2204
Micro Genius $79
Standard version for DOS or Windows $195
Deluxe version $395
Z-World
Davis, CA
(916) 757-3737; fax (916) 753-5141
Xplor-32
Board only $59.95
Board with cables, power supply,
manual, and disk $99.95
Blue Earth Research
Mankato, MN
(507) 387-4001; fax (507) 387-4008
739-0298@mcimail.com
photo_link (25 Kbytes)
The Micro Genius (left) and Xplor-32. Inset: the Domino-52 (left) and Basic Stamp.
Rick Grehan is
a senior technical editor for BYTE reviews. He can be contacted on the Internet or BIX at
rick_g@bix.com
.
Let's Get Small
