Sending Output - Element 14 Raspberry Pi User Manual

Sending output

Use the GPIO pins to light up some LEDs.
The Pi's tiny size makes it ideal for making your own embedded
devices. This can be a great way of creating small computing devices
to solve specific problems, as we saw with the camera controller.
However, there is the slight problem that
it can be hard to know what's going on
inside your Pi without a screen. Fortunately,
the designers of the Pi thought of this
problem and have added the facility to get
information on and off a Pi without the bulk
of usual PC peripherals. This is done via
General Purpose Input and Output (GPIO).
You may have wondered what the spiky
pins near the SD card reader are for – well,
you're about to find out. This basic circuit
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Raspberry Pi User Guide.indd 26
can be used to display information from
any source, but here we're going to use it
to find the final byte of the IP address. This
is useful if you want to remotely access
your Pi, but can't configure it with a static
IP because, for example, you have to
move it between networks. Typically, you
can find out the first three bytes from the
netmask, but the final one can be elusive
unless you have a monitor attached.
Figure 1. This shows
■
how half of the LEDs
are wired up. The
additional ones are
added in exactly the
same manner.
08/07/2014 14:44