Figure 3. Basic Atom
Figure 6. Basic Atom
Figures 5A and 5B. Atom Interpreter chip and Nano Interpreter chip.
circuit. Parallax sells this board
for $69.99 on their website.
The one shown in Figure 2 is
the USB version but there is
also a nine-pin serial connection
Basic Micro doesn’t offer a
24-pin specific board like the
BOE. Instead, they offer a board
that accepts the 24-pin, 28-pin,
and 40-pin Atom modules. I
haven’t mentioned these other sizes previously, but both
Parallax and Basic Micro offer larger module versions. The
larger modules eliminate the need to solder the wires on
the Atom 24 to access the extra analog-to-digital pins. The
Atom board shown in Figure 3 sells for $49.95. It doesn’t
have the servo connections but does have a larger
breadboard area. I’ve used an older version of this board
so I don’t know all the new features. The Basic Micro
website shows the current version of the board can accept
the nine-pin RS-232 style cable or a USB connection.
There are numerous other third party development
board options for both of these modules, so just shop
around and I’m sure you’ll find the perfect development
board for your project. Since they are pin-compatible, in
most cases you can use a Stamp in an Atom board and
an Atom in a Stamp board.
Figures 4A and 4B. BASIC
Stamp 2 Interpreter and
Some people complain about the roughly $50 cost per
module. When you are planning on building something in
volume, then that $50 can get very expensive. But in both
cases, you don’t have to stop at the module level. Both
companies offer the raw chips at a lower price so you can
build your design cheaper. The Stamp 2 interpreter chip and
external EEPROM are shown in Figure 4. You can get these
in volume discounts from Parallax; the single quantity
price is $11.99 for the microcontroller and $1.10 for the
EEPROM. You’ll need to add the 20 MHz resonator, external
regulator, and the programming interface circuit but even
then you are saving a lot versus the $50 module.
The Atom doesn’t use the external EEPROM so all you
need to buy is the interpreter chip. The Atom interpreter
chip is $20 and is shown in Figure 5. This also requires the
20 MHz resonator, voltage regulator, and programming
interface though Basic Micro also offers a module
(Figure 6) that has the programming circuitry built in,
so programming the interpreter is much easier and you
don’t have to include that circuitry on every design. They
designed it originally for the Atom Nano version of the
interpreter chip, but it will work on some of the Atom
interpreters, as well.
The Nano is a lower cost interpreter version that
doesn’t need the external 20 MHz resonator because it uses
its internal 8 MHz oscillator. This slows down the program
by 60% so you have to account for that in all the timing
delays of your program. The Nano 28-pin is shown in Figure
5 next to the Atom interpreter chip. The Nano 28 chip
costs $8.95, so sacrificing a little speed saves you a lot of
money. The Nano uses the same commands and same
programming software so you don’t have to learn anything
Figures 7A and 7B.
and Starter Kit.
70 SERVO 08.2009