• If you use the same
RazzPi- 20 board in both
PICAXE-Pi and pure
PICAXE projects, make
sure the jumpers on the
two three-pin headers are
in the correct position for
your current project.
• If you never intend
to use the RazzPi- 20 in a
PICAXE-Pi project, you
could assemble the board
without the two three-pin
headers, and replace each
one with a soldered-in
wire jumper that connects
the two lower positions
for each three-pin header.
Since the RazzPi- 20 board can
be used with both PICAXE and
PICAXE-Pi projects, let’s take a look
at the process of assembling the
PCB. A complete parts list is shown
in Figure 13, and all the parts (except
the PICAXE processor) are available
on my website. (PICAXE processors
are available at www.phander
son.com and www.sparkfun.com.)
As usual, read through the following
list of assembly instructions to be
sure you understand the entire
procedure before beginning to put
the board together.
1. On the top of the board,
install the diode (observing polarity),
the two three-pin headers, and the
stereo jack. (Do not install the IC
2. Snip excess leads on the
bottom of the PCB.
3. On the bottom of the board,
install the SMD cap and the three
4. Insert headers H1, H4, and H5
into the middle area of a breadboard
so their positions match the spacing
on the PCB layout.
5. Place the PCB on the three
headers so that the short ends of all
the pins are inserted into the
corresponding holes in the PCB.
6. Solder headers H1, H4, and
H5 in place.
7. Remove the PCB from the
breadboard and insert headers H2
and H3 into the upper power rails of
the breadboard so their positions
match the spacing on the PCB layout.
8. Place the PCB on headers H2
and H3 so that the short ends of the
header pins are inserted into the
corresponding holes in the PCB.
9. Press down on the PCB so all
the headers are fully inserted into the
10. Solder headers H2 and H3 in
place. (Header H2 will require extra
care because the available space is
11. Remove the PCB from the
breadboard, insert the IC socket from
the top of the PCB, and solder it in
place on the bottom of the board.
12. Clean the top and bottom of
Pure PICAXE Setup
With the RazzPi- 20
In this experiment, we’re going
to implement a 15 LED “Cylon Eye”
project as a simple demonstration of
how to use the RazzPi- 20
board in a pure PICAXE
project. Figure 14 is a
photo of my breadboard
setup for the experiment.
In addition to the power
supply and the RazzPi- 20,
the only other components
we need are two 10-bar
LED displays, two 10-pin
SIP resistors (nine 470Ω
resistors each, with a
common ground pin), and
four jumper wires.
The setup is simple.
The two LED bar displays
are lined up so that the
anode of the left-most
LED is connected to pin
C. 4 on the RazzPi- 20, and
the two SIP resistors are installed so
that their ground pins are at opposite
ends and connected to ground with
a short jumper. (The ground
connection on the left end is one
breadboard position to the left of the
In Figure 14, you can also see
how the two slightly longer jumpers
connect pins C. 7 and C. 5 on the
RazzPi- 20 to LEDs #6 and #7
(counting from the left), which would
otherwise not be connected to a
20M2 output pin. Of course, we
can’t use pin C. 6 for this experiment
because it’s fixed as an input. As a
result, we’re using eight pins on port
B, and seven pins on port C to
implement our 15 LED Cylon Eye.
Finally, Figure 14 demonstrates
the amount of space the RazzPi- 20
saves on a breadboard. Without it
(or a similar PCB), there would be no
way we could install a 20-pin
processor and two 10-LED bars on
the small breadboard we usually use
in our projects.
When you’ve completed your
breadboard setup, download the
software for this experiment
( Cylon15.bas) to your 20M2, and
have fun watching the Cylon Eye
scan back and forth!
When you tire of doing that, I
want to clarify one point about the
18 November 2014
■ FIGURE 14. RazzPi- 20 pure PICAXE setup.