Hardware Reference
In-Depth Information
Figure 3-8.
This is a closer look at part of the diagram in
Figure 3-7
. When
making the LED blink, the flow of electric current makes a complete loop (or
circuit) from the digital output pin to ground.
The energy from the flow of electrons in a circuit can be used by the LED,
which is converting that electrical current into light energy.
If you were able to see electrons in the wires, the flow that
makes up electrical current is actually moving
from
ground
to
pin 13. When we think of the flow of electricity while making
circuits, we think in the reverse of reality: that the flow of elec-
trical current goes from a positive charge source (like digital
pin 13) to ground. This is by convention only. When electricity
was first discovered, early physicists weren't sure which di-
rection electricity flows and so they made a guess. We later
found out that they were wrong. However, that early conven-
tion is still used.
Most of the time, the circuits you'll be making with Galileo will be using 5 volts.
The IOREF jumper, as shown in
Figure 2-1
, will let you change the logic voltage
level for compatibility with shields that use 3.3 volts. Throughout this topic,
you'll be using Galileo in its 5-volt mode.
