but use the M model for its additional
memory. Now you can apply power
and try programming your Mini. Note
that the color diagram of the parts
layout is marked with a GND on
the ground pin of the PICAXE
programmer. If you plug the
programming cable in backwards, the
PICAXE will not program.
The simplest programming test is
to write the command DEBUG and
download it. The DEBUG command
tests that the PICAXE is good and
that two-way communication is
possible. The result is that you will
see the progress of the download
and then the debug window open.
There will be one debug statement
and the values of the memory
displayed (which will be all zeros).
After testing the connections on
the PCB, mark your Mini PCB with its
power and ground indicators. Place a
green dot on the PCB next to the
ground row of the receptacles and
headers (don't forget the programming header). Place a red dot next to
the +5V row of the receptacles and
header. Look at the color parts
placement diagram for an example.
To protect the Mini from loose
objects inside the BalloonSat, cover
the bottom of the PCB in a layer of
Foamcore,the material used to mount
posters. It consists of a thin sheet of
Styrofoam backed with paper. The
material is easily cut with a sharp
X-acto knife. Carve small pockets in
the Foamcore where the strain relief
wires exit the PCB. Use hot glue to
attach the Foamcore to the underside
of the PCB and fill the remaining
gaps along the edges with additional
The symbolic code for a
BalloonSat Mini looks like this:
Now all that remains is managing
the LED, power switch, and commit
receptacle. I make an instrument
panel to do this from a two inch by
three inch sheet of 40 mil thick
polystyrene. I like the stuff because it
is easy to cut and can be drilled by
spinning the tip of the X-acto blade.
Make the hole for the switch and
phono jack receptacle large enough
to mount them. They lock into place
with nuts, so don’t worry if their hole
is a little too large. Make the hole
for the LED just smaller than the
diameter of the LED so it fits tightly.
However, if the hole for the LED is
just a little too large, you can use
a bit of hot glue to hold the LED
The commit pin is a 1/8 inch
phono jack. The jack's tip and base
is shorted together internal to the
jack housing. That way, when the
jack is inserted into the mono jack
receptacle, the PICAXE-08M's
commit pin (which is pulled high) is
shorted to ground. Unscrew the jack
housing and solder a doubled-over
wire across the tip and base
connections. Use a 6” length of
wire to do this so when the wire is
doubled over, it extends outside
the housing. Squirt a little hot glue
around the soldered connection of
the jack, but be careful not to use so
■ This BalloonSat Mini 2 is ready to rock and roll. It will record the air
temperature and cosmic ray flux during a mission while also taking pictures
from near space. To keep the cables between the instrument panel and
BalloonSat Mini manageable, you might try using some spiral wrap as I did.
If the commit pin has been
pulled, then download data.
Wait for commit pin to be
Start at memory location 0.
Digitize analog value(s).
Write values into memory.
Increment memory address.
Record an image.
Repeat until memory is filled.
Go to the end of the program.
Start at memory location 0.
Step through memory addresses,
reading value stored in each
Transmit value to terminal
Repeat until end of memory is