over the two wire bus at frequencies up to 400 kHz. This allows the device to freely exchange
information with other devices in the network within a small area. We discuss the TWI system later
in the book. Analog to Digital Converter—ADC
The ATmega328 is equipped with an eight channel analog to digital converter (ADC) subsystem.
The ADC converts an analog signal from the outside world into a binary representation suitable for
use by the microcontroller. The ATmega328 ADC has 10 bit resolution. This means that an analog
voltage between 0 and 5 V will be encoded into one of 1024 binary representations between (000)
and (3FF)
. This provides the ATmega328 with a voltage resolution of approximately 4.88 mV.
We discuss the operation, programming, and application of the ADC later in the book. Interrupts
The normal execution of a program step follows a designated sequence of instructions. However,
sometimes this normal sequence of events must be interrupted to respond to high priority faults
and status both inside and outside the microcontroller. When these higher priority events occur, the
microcontroller must temporarily suspend normal operation and execute event specific actions called
an interrupt service routine. Once the higher priority event has been serviced, the microcontroller
returns and continues processing the normal program.
The ATmega328 is equipped with a complement of 26 interrupt sources.Two of the interrupts
are provided for external interrupt sources while the remaining interrupts support the efficient oper-
ation of peripheral subsystems aboard the microcontroller. We discuss the operation, programming,
and application of the interrupt system later in the book.
Much like an artist uses a sketch box, we will use an Arduino Hardware Studio throughout the book
to develop projects. In keeping with the do-it-yourself (DIY) spirit of Arduino, we have constructed
the Studio using readily available off-the-shelf products as shown in Figure 1.14.The Studio includes
the following:
A yellow Pelican Micro Case #1040,
An Arduino UNO R3 evaluation board,
Two Jameco JE21 3.3 x 2.1 inch solderless breadboards and
One piece of black plexiglass.
We purposely have not provided any construction details. Instead, we encourage you to use
your own imagination to develop and construct your own Arduino Hardware Studio.
Figure 1.14: Arduino Hardware Studio.

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