•RAM Size: 368 bytes (300 variables)
•14K of Program Space
•256 bytes of User EEPROM
•Number of I/O Pins: 16 + 2 dedicated serial
•Source/Sink Current per I/O: 25 mA/25 mA
• 66 Basic Commands
•Package: 24-pin DIP
•Three Hardware Timers
•Analog-to-Digital Converter (three channels)
•32-bit Integer Bit Math
•32-bit Floating Point Math
As you can see, the Atom took what made up the
Stamp and then added some extras. The Atom used a
higher level Microchip PIC microcontroller at its core which
gave the Atom more memory and more I/O features. You
may not need all these extras, but it’s nice to know you
have an upgrade path. For many people, once they start
building more complex programs they eventually want to
use floating point math. Interrupts are another useful
feature. And best of all analog to digital conversion though
the Atom 24 requires you to solder some extra wires to get
to the special pads on the circuit board.
The speed is different between the two modules, along
with the added memory size. The Stamp 2 uses an external
EEPROM chip to store the command tokens and then
retrieves them one at a time from that EEPROM. The Atom
software compresses the Basic commands into a single file
that fits inside the PIC memory and then retrieves each
tokenized command from internal Flash memory. Accessing
commands from external EEPROM is significantly slower
than accessing memory from within the Flash memory, so
this is why the Atom runs faster.
The Atom’s compression technique is similar to a
compiler converting high level language to binary, so this
allows it to access all the Flash memory in the PIC. This is
where the 14k of total memory space comes from. Exactly
how many commands that equates to is hard to determine.
I’ve found that the Atom offers more than 500 instructions,
but the first 2K is used up very fast. After that, it gets
much more efficient. I would estimate that the Atom can
accept about 800-1,000 command lines, but it really
depends on which commands you use. Some use far less
memory than others.
Both modules use unique software development tools
that are free to download. The Stamp uses the Parallax
programming software for writing code and the Atom
uses the Basic Micro programming software. In both
cases, they offer a one-click programming feature which
is a nice, easy interface for the beginner.
The Stamp and Atom both communicate and program
through a serial connection. This can be an RS-232 serial
connection or a USB connection. (You just have to use the
proper cable.) I’ve programmed both with a third party USB
to RS-232 converter cable and also a standard nine-pin
straight through serial cable. I find the communication
worked really well for both. The Stamp seemed to program
a bit faster for the same size program.
The programming software is available on each of their
websites, and they run on a Microsoft based PC. Neither
offers a pure Macintosh version but I have used an Intel-based iMAC with Windows installed on a partition and
programmed them both successfully.
The Stamp 2 offers a DEBUG feature that allows you to
see a variable while it is running for debugging your code.
The Atom offers a full debugger interface that allows you
to see multiple variables and internal registers, plus also
allows you to single step through your code when trying to
find a problem.
This is an area where the Stamp wins. The example
code and the supporting documentation for the BASIC
Stamp is much better than what is offered for the Atom.
The Stamp has been around longer, plus Parallax made the
investment in producing application notes. Because the
PBASIC code and the Atom Basic code are so similar, you
can usually convert PBASIC to Atom Basic easily. Having
documentation from Parallax is a clear advantage for
There are numerous development boards available for
both modules. The Parallax Board of Education (BOE)
development board is a common platform that is often
used in robotics (Figure 2). It has a socket for the module
and also connectors for attaching servo motors. The
breadboard area allows you to build your own interface
Figure 2. BASIC Stamp 2 Board of Education
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