Vintage Computing
access to 18 Propeller I/O pins, the LEDs and switches,
and power and ground connections. The breadboard is
small, but it’s all you need for many computer-controlled
hardware experiments. (In fact, it’s the same one that’s on
several Parallax hobbyist boards.) Figure 6 shows the
History of the
Pocket Mini Computer
Amigo kit and what comes in the box.
Since you are reading this magazine, the chances are
excellent that you already possess the background and
skills to easily build your own Amigo. The assembly
instructions are meant to be complete and easy to follow,
and they include lessons learned from builders before you.
The Amigo is a direct descendant of the Pocket Mini
Computer (PMC): a project by Jeff Ledger that combined
the work of several Propeller gurus to offer a series of
retro computers running a version of BASIC. A bit of
history may be helpful to understand the technical
elegance behind this seemingly simple little device.
With the exception of the SD card socket, all parts are
through-hole — not surface-mount — and the 4” x 4”
board size allows plenty of room to work comfortably. I
am a slow and methodical builder, but my 15 watt iron,
magnifier, and I can easily finish an Amigo kit in a single
afternoon, with plenty of time left over for some
refreshments after the tools are put away.
In 2012, Gadget Gangster offered the first official
Pocket Mini Computer created by Ledger, who himself was
a longtime Propeller project designer and more recently,
the proprietor of propellerpowered.com. (You may have
come across Ledger on various computer Internet forums
under the nickname of Oldbitcollector. He has been a
prolific designer, author, and contributor.)
Time for a Test Drive
The initial PMC combined a Parallax QuickStart board
with an expansion board that interfaced a PS/2 keyboard,
VGA monitor, Wii controller, audio jack, and SD card. In
addition to the open source software objects that
supported all those interfaces, the PMC software
contained a tinyBASIC interpreter that Ledger and others
extended from the original 2006 work of Tomas Rokicki
and Mike Green.
So, once you’ve built your Amigo, what can you do
with it? The first thing you’ll notice is that Color BASIC is
definitely tiny — only 26 variables, just 4K of program
memory, no support for strings, 32-bit integer arithmetic
only, no arrays, no explicit DATA statement. However, for
an initial mentoring platform, those are all good things,
not bad ones. Excluding the various operators, Color
The design challenge for Color BASIC was figuring out
how to shoehorn all that capability into the eight cogs and
32K memory of the Propeller chip. Several “big brains” in
the Propeller user community volunteered their expertise
where needed to help make Color BASIC a reality, and in
mid-201, 2 the first PMC was on the market.
BASIC has about 50 commands. (Please see online
resources for an overview of most Color BASIC
commands. You’ll be glad you did!)
It’s fun and compact, and easy to learn and enjoy. It
also includes everything you need to really understand the
fundamentals of computer programming and hardware
control, without the continuing disappointment of yet
another layer of complexity to learn. With a little guidance,
young students can truly “master” the Amigo, and with that
mastery comes a self-confidence and “big picture”
understanding that will serve them well going forward.
In 2013, Ledger and Propellerpowered released an
updated PMC which paired the Parallax QuickStart board
with an improved expansion board, adding 32K of SRAM
and upgrading the VGA from 48 to 64 colors, with an
option for 256. This update also added bus headers to
allow direct access to available Propeller I/O pins. In 2014,
the PMC was updated again to move to an easier-to-build
single board configuration (no longer using the QuickStart
board) and to add several features users were asking for.
These included more access to I/O pins; onboard
breadboard, LEDs, and switches; an interface option to the
Raspberry Pi (or other computers); and sockets for port
expansion and Flash memory ICs.
Here is an actual Amigo starter program to give you
an idea of how simple Color BASIC is to understand and
use. Once you get your kit built and see the READY
prompt on your VGA monitor, press <F1> on your
keyboard to start the editor, then enter this Color BASIC
version of the classic first program:
The resulting Propeller Experimenter Board (PEB 2014)
from propellerpowered.com was a superb technology
mentoring platform, but was no longer available in late
2014. The Amigo is a simplified version of that PEB 2014
developed by Dane Weston in mid-2015 to provide a
BASIC-driven mentoring platform for Nuts & Volts
readers.
10 REM HELLO WORLD! ***
20 COLOR 63,0 REM <~~~ WHITE TEXT, BLACK
BACKGROUND
30 CLS REM <~~~ CLEAR THE SCREEN
40 FOR N=1 TO 100
50 A=RND(34) REM <~~~ RANDOM COLUMN
60 B=RND(37) REM <~~~ RANDOM ROW
70 C=RND(63)+1 REM <~~~ RANDOM TEXT COLOR
(NOT 0)
80 LOCATE A,B
90 COLOR C,0
100 PRINT “HELLO WORLD!”;
110 NEXT N
120 PAUSE 3000 REM <~~~ WAIT 3 SECONDS
130 GOTO 20 REM <~~~ DO IT AGAIN
When you’ve entered the code, press <F1> again to
return to Color BASIC and run your program. If all goes
well, you should see lots of instances of “HELLO
WORLD!” in different colors at random screen locations,
followed by a short pause, then repeating. Now, press
December 2015 41
