Hardware Reference
In-Depth Information
Before You Begin
Designing a custom-shaped Arduino derivative often begins with gaining a general sense
of the desired size and shape. For example, in designing a housed board for Replay, clay
and foam form models completely void of any electronics were prototyped to help spark
ideas around the use of the toy itself. This exploration ultimately led to a shape that enabled
the construction of interesting structures using a limited number of pieces.
Once you gain an understanding of the physical constraints of your design, ask your-
self the following questions regarding the electronics:
How complex is the program you need to run (in terms of memory usage and stor-
age)?
How many input and output pins do you need?
Will the sensors, actuators, and power reside on or off the board?
How do you plan to manufacture the board (e.g., double-sided or single-sided,
in-house or using a service)?
Your answers to the first two questions will help determine which type of microcontroller you use for your Arduino
derivative. If you're running a relatively simple program with few input or output pins, you may be able to incorporate
an ATtiny microcontroller, which is less powerful but also smaller and less expensive than the ATmega328 used on Ar-
duino Unos.
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Deciding whether the sensors, actuators, and power will be offboard or onboard com-
ponents further determines your size constraints. Offloading components enables the
board to have a smaller footprint but also requires the design of connectors between the
board and the sensors, actuators, or power source. For example, for Replay, the power and
signal were passed between pieces using a 4-pin audio connection. While the audio jack
was a surface-mounted component securely fixed to the board, the audio connector was
an offboard component that was connected via ribbon cables, thereby conserving space on
the custom board.
After you determine which components are needed for your application, identify
space-limiting components—that is, components that dimensionally take up the most
space. Remember to account for the headers used to program your microcontroller. If
you're using an ATtiny microcontroller, you have the option of using a small outline in-
tegrated circuit (SOIC) clip programmer, which eliminates the need for separate program-
ming headers. If you are trying to minimize the footprint of your board, consider using
