The construction of the
stripboard circuit is very
straightforward, so a list of
instructions isn’t necessary. As usual,
install the parts by starting with the
lowest ones (the jumper wires), and
work your way up to the tallest (the
four-pin female header). However,
there is one point that I should
mention: The holes at B3 and B6
need to be slightly enlarged so that a
header pin and a resistor lead will fit
in the same hole.
A 1/16 inch drill bit is large
enough — just be sure to drill the
board with the traces facing up so
you don’t tear out the traces around
the holes.
If you prefer not to take this extra
step, just cut the stripboard so that
the traces include nine holes rather
than eight, and move the four-pin
right angle male header one position
to the left.
When you’ve completed
construction of the stripboard circuit,
you can test it with the same program
that we used in Experiment 2.
Figure 8 is a photo of my
completed stripboard circuit, and
Our USB-to-serial inverter circuit
provides a simple and inexpensive
way to power and program our
PICAXE breadboard circuits with a
single connection. If your primary
computer is a laptop, it also enables
the possibility of mobile project
development. (I’ve actually worked
on the hardware portion of PICAXE
projects while commuting on the
local railroad!)
Before wrapping up Experiment
3, there’s one final point that needs
to be mentioned. If you use the
inverted Prolific cable to develop a
PICAXE project that will ultimately be
powered by batteries (or any other
power source), don’t forget that if
you remove the USB cable and
inverter board from your circuit, you
will need to tie the processor’s Serin
pin to ground (via a 100K resistor) in
order for the circuit to function
correctly.
Of course, the same thing is true
for the AXE027, the FTDI cable, or
any other programming connection.
Where's the
Power Switch?
As I mentioned
earlier, there’s no
power switch on the USB-to-serial
inverter board; to disconnect power
from the breadboard, you have to
physically disconnect the cable. I’m
sure you’re wondering why, so let me
explain.
The inverter board is part of a
larger project that I’ve been working
on recently. Back in the June 2010
Primer, I introduced the FTDI-based
AxMate programming adapter, and
for some time now, I’ve wanted to
extend the AxMate concept so that it
can work with a variety of USB-to-serial adapters.
Since all PICAXE processors
require the serial programming data
to be inverted, and (as far as I know)
the FTDI cable is the only adapter
that supports software inversion of
the data lines, I decided to develop a
two-board system which includes an
adapter board containing the
circuitry required by a specific USB-to-serial cable (e.g., FTDI, Prolific,
AXE027), and an interface board
containing the circuitry required by
all USB-to-serial cables (i.e., a switch,
an LED power indicator, and a bypass capacitor).
So far, I’ve developed three
different adapter boards:
14 March 2015
■ FIGURE 9. Prolific
stripboard connected to
breadboard.
■ FIGURE 8. Completed Prolific adapter.