We’re going to use the
gpio
program, which
is part of
WiringPi
. You can find out more
about this from the website:
bit.ly/RP8UKJ
.
The software comes as source code, so
we’ll have to unzip it and compile it with:
tar xvf wiringPi.tgz
cd wiringPi/wiringPi
make
sudo make install
cd ../gpio
make
sudo make install
We’ll also use
bc
, so install it with:
sudo apt-get install bc
Now, that’s enough about software – on
with the hardware! Just a quick word of
warning before we start: it is possible
to break your Pi by connecting the
wrong wires together, so make sure you
double-check before powering up.
The circuit for this is very simple – you
just have to connect each output to
the positive leg of an LED, then the
negative leg of the LED (shorter) to a
1 KOhm resistor, and finally the other leg
of the resistor to the common ground.
See figures 1, 2 and 3 for details.
Once you have your fully-set-up board
connected to your Pi, you can make things
happen. To start with, we’ll just use the
final pin. This is pin 7 (the layout of the pins
doesn’t follow a numbering pattern). Open
up a terminal, and set it to output with:
gpio –g mode 7 out
Then you can turn it on with:
gpio –g write 7 1
and off again with:
gpio –g write 7 0
If you’re like us, you’ll do that repeatedly until
the novelty of it wears off. Once it has, you’re
ready to run the script. It contains four parts.
■
Figure 2. Connect
the bread board to
these pins. We used
commercially-
available single-pin
connectors, but you
could also solder
connectors on, or use
an old IDE cable.
27
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