Hardware Reference
In-Depth Information
UnderstandingComponentPin-outs
All datasheets will include the pin-out for the device in question, which clearly
illustrates the functions of each pin. Particularly for microcontrollers, pins may
have multiple functions, so understanding the pin-out can be critical for grasp-
ing what each pin can and cannot do. Consider the pin-out of the ATMega 328p
(see Figure A-3). Understanding the pin-out of the microcontroller at its heart
will make it easier to understand the Arduino Uno schematic, which you'll look
at in the next section.
Figure A-3: ATMega 328p DIP pin-out
Note that the pin-out indicates how you can find the pin number on the actual
chip. The half circle at the top of the pin-out corresponds to a similar half circle
on the actual integrated circuit. Look at the chip in your Arduino and you'll
see this half circle; now you know that the pin immediately to its left is pin 1.
You'll also probably notice some abbreviations that you may not be familiar
with. They are defined here:
VCC refers to voltage supply to the chip. In the case of the Arduino, VCC
is 5V.
AVCC is a separate supply voltage for the ADC. For the Arduino, it is
also 5V.
AREF is broken out to a pin. So, you can choose an arbitrary voltage below
5V to act as the reference for the ADC if you desire.
GND is, of course, the ground connection.
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