2. Embedded System
Embedded means something that is attached to another thing. An
embedded system can be thought of as a computer hardware system
having software embedded in it. An embedded system can be an
independent system or it can be a part of a large system. An embedded
system is a microcontroller or microprocessor based system which is
designed to perform a specific task. For example, a fire alarm is an
embedded system; it will sense only smoke.
So we can define an embedded system as a Microcontroller based,
software driven, reliable, real-time control system.
3. Some examples of embedded systems are MP3 players, mobile phones,
video game consoles, digital cameras, DVD players, and GPS. Household
appliances, such as microwave ovens, washing machines and dishwashers,
include embedded systems to provide flexibility and efficiency.
These kinds of systems can be classified into three different types: small
scale embedded systems, medium scale embedded systems, and
sophisticated embedded systems.
1) Small scale embedded systems: These usually use 8 bit or 16 bit
microcontrollers, and have minimum hardware and software. They are so
small and require little power they may be powered by a battery.
2) Medium scale embedded systems: They use either one or a few 16 bit or
32 bit microcontrollers, and hardware and software is more complex as
compared to small scale embedded systems.
3) Sophisticated embedded systems: The most complex of the three
classifications mentioned.
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10. Characteristics of an Embedded System
• Single-functioned − An embedded system usually performs a specialized operation and does the
same repeatedly. For example: A pager always functions as a pager.
• Tightly constrained − All computing systems have constraints on design metrics, but those on an
embedded system can be especially tight. Design metrics is a measure of an implementation's
features such as its cost, size, power, and performance. It must be of a size to fit on a single chip,
must perform fast enough to process data in real time and consume minimum power to extend
battery life.
• Reactive and Real time − Many embedded systems must continually react to changes in the
system's environment and must compute certain results in real time without any delay. Consider an
example of a car cruise controller; it continually monitors and reacts to speed and brake sensors. It
must compute acceleration or de-accelerations repeatedly within a limited time; a delayed
computation can result in failure to control of the car.
• Microprocessors based − It must be microprocessor or microcontroller based.
• Memory − It must have a memory, as its software usually embeds in ROM. It does not need any
secondary memories in the computer.
• Connected − It must have connected peripherals to connect input and output devices.
• HW-SW systems − Software is used for more features and flexibility. Hardware is used for
performance and security.
13. • Sensor − It measures the physical quantity and converts it to an electrical
signal which can be read by an observer or by any electronic instrument
like an A2D converter. A sensor stores the measured quantity to the
memory.
• A-D Converter − An analog-to-digital converter converts the analog signal
sent by the sensor into a digital signal.
• Processor & ASICs − Processors process the data to measure the output
and store it to the memory.
• D-A Converter − A digital-to-analog converter converts the digital data fed
by the processor to analog data
• Actuator − An actuator compares the output given by the D-A Converter to
the actual (expected) output stored in it and stores the approved output.
14. •Embedded systems contain two main elements:
•Embedded system hardware: As with any electronic system, an
embedded system requires a hardware platform on which to run. The
hardware will be based around a microprocessor or microcontroller.
The embedded system hardware will also contain other elements
including memory, input output (I/O) interfaces as well as the user
interface, and the display.
•Embedded system software: The embedded system software is
written to perform a particular function. It is typically written in a
high level format and then compiled down to provide code that can
be lodged within a non-volatile memory within the hardware.
15. Embedded systems hardware
When using an embedded system there is a choice between the use of
a microcontroller or a microprocessor.
•Microcontroller based systems: A microcontroller is essentially a
CPU, central processor unit, or processor with integrated memory or
peripheral devices.
•Microprocessor based systems: Microprocessors contain a CPU but
use external chips for memory and peripheral interfaces. As they
require more devices on the board, but they allow more expansion
and selection of exact peripherals, etc, this approach tends to be used
for the larger embedded systems.
16. Embedded systems software
One of the key elements of any embedded system is the software that
is used to run the microcontroller.
There is a variety of ways that this can be written:
•Machine code: Machine code is the most basic code that is used for
the processor unit. The code is normally in hex code and provides the
basic instructions for each operation of the processor. This form of
code is rarely used for embedded systems these days.
•Programming language: Writing machine code is very laborious and
time consuming. It is difficult to understand and debug. To overcome
this, high level programming languages are often used. Languages
including C, C++, etc are commonly used.
17. Embedded systems design tools
•Many embedded systems are complicated and require large levels of
software for them to operate.
•Developing this software can be timing consuming, and it has to be
very accurate for the embedded system to operate correctly. Coding
in embedded systems is one of the main areas where faults occur.
•To help simplify the process, software development tools are
normally used. These help the software developer to programme
more quickly, and also more accurately.
