How do Microcontrollers
Differ from the Arduino?
The Arduino is often referred to as an ecosystem. It is
similar to a natural ecosystem in the way in which the
various elements inter-relate and depend on one another.
The core elements in the ecosystem are the physical
boards and the software integrated development
environment (the IDE and the Arduino libraries), which are
then surrounded by the documentation, the support
structures, and the larger Arduino community (Figure 1).
In moving away from the Arduino ecosystem, you are
leaving these behind, but that doesn’t mean you’re
moving into an environment without these interrelationships. These elements exist in some form or
another, but are not as neatly packaged or as accessible.
A microcontroller by comparison is just one of the
components that make up a physical Arduino board — it is
the most important element as it is effectively the “brains”
of the board. In order for a microcontroller to function, it
needs only a few simple components and regulated
power. The Arduino Uno that I used supported the
microcontroller by housing these parts and providing it
with a steady clean supply of power.
My Uno went a few steps further by giving me a way
to communicate with the onboard microcontroller. A
stand-alone microcontroller can’t communicate with a PC,
so Arduino cleverly incorporated USB connectors to make
this happen. The main reason to open a communication
channel is to allow you to program the microcontroller —
there’s not much point working with one otherwise!
Secondly, by using a serial terminal, you can
communicate with your sketch while it’s running — I use
this extensively for debugging. Also on the Uno is a
second microcontroller that handles the translation from
serial to USB. On newer boards (like the Leonardo), the
main microcontroller has the ability to do this.
This might all sound rather complicated, but by the
end of this article you’ll have built your own mini Uno on
a breadboard — and be able to communicate with it.
Why Even Think About It?
So, you’ve got a good partnership going with your
Uno. Why would you even want to consider making the
leap into the unknown? Using my irrigation controller as
Physical Form: The Uno measures 55 mm by 75 mm
and is a chunky rectangular shape. In contrast, the
microcontroller on the Uno only measures 10 mm by 35
mm, and can be built into a board of almost any shape
you want (Figure 2).
Figure 3 had a shift register, an EEPROM chip, a real
By Andrew Retallack
March 2015 37
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FIGURE 2. Square peg, round hole: Form factor is
a reason to work with raw microcontrollers.
FIGURE 3. Integrating a microcontroller into a
PCB with other components.