Computers
embedded in
special
purpose
devices
This presentation introduces computers that
are embedded in special purpose devices.
Embedded computers
Skills: none
Concepts: embedded computer, RAM, ROM, sensor,
the “Internet of things”
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike
3.0 License.
A technology
presentation
We see that they have the same functional
components as general purpose computers,
but you cannot change their function by
loading a new program.
We will see several examples of devices with
embedded computers and the sensors they
use.
This is a technology presentation.
Where does this topic fit?
• Internet concepts
– Applications
– Technology
– Implications
• Internet skills
– Application development
– Content creation
– User skills
Embedded
computers
have the
same
functional
components
as general
purpose
computers.
Computer components – information flow
This diagram stresses the direction of
information flows within a computer.
CPU
Input
devices
Memory
system
Storage devices
(programs and data)
Output
Devices
With a laptop or desktop computer, the user
interacts with the input and output devices, for
example typing information on a keyboard,
pointing at the screen with a mouse, or reading
printed or displayed information.
Computers that are embedded in special
purpose devices have the same functional
components, but the inputs, outputs or both
are often to and from things, not people.
Devices with
computers
embedded in
them
A microwave
oven
Things with computers inside
(embedded)
Computers are embedded in all of these
devices.
Cars, cameras, cell phones, watches, TV sets,
microwave ovens, and ATM machines all
contain embedded computers.
Take a microwave oven for example.
When the user pushes the “start” button on a
microwave oven, the embedded computer
detects that it has been pushed and reads the
settings on the control panel.
It then adjusts the power level, sends a signal
to turn the oven on, tracks the elapsed time,
sends a signal to turn the oven off at the proper
time, and outputs a beeping sound to let the
user know the food is cooked.
The computer is able to output signals to adjust
the power level and turn the oven on and off.
There is a computer embedded in this camera.
A camera
It can read input from the various dials and
buttons used to select options.
Light coming through the lens strikes an image
sensor that reads the intensity and color of the
light at each pixel point.
That information is output to the display on the
back of the camera along with focusing
information.
When the user pushes the shutter button, the
image is stored in flash storage.
The user can connect the camera to a laptop or
desktop and transfer images stored inside the
camera to the computer.
If the camera has a cellular or WiFi radio, it can
also upload stored images to the Internet.
There are
many
computers in
a modern car.
Computers
in cars
This slide lists some of the computer controlled
systems in a modern car.
Dozens of computers running millions of lines of
software are embedded in modern cars.
Air-bag control
Anti-lock brakes
Automatic transmission
Alarm
Climate control
Collision-avoidance
Cruise control
Communication (e. g., onStar)
Dashboard instrumentation
Stability control
Ignition system
Engine control
Seat control
Entertainment system
Navigation
Power steering
Tire-pressure monitoring
Windshield-wiper control
They are a major cost component and a possible
source of bugs and vulnerable to hacking.
In spite of that complexity, they make new
features possible and increase safety and
reliability.
General
versus
specialpurpose
computers
General purpose
computer
Special purpose
computer
When we use our laptop or desktop computers,
we load different programs into memory to do
different jobs – a word processing program for
writing, an image editor for drawing, and so forth.
Memory that can be changed is called RAM
(random access) memory.
Programs in volatile,
random access memory
(RAM)
Programs in fixed,
read only memory
(ROM)
When you turn the computer off, the contents of
RAM memory are erased – it is volatile.
The programs in an embedded computer don’t
change – your camera is always a camera, never a
microwave oven.
Since the function does not change, the camera
program is permanently stored in read only
memory (ROM).
ROM contents are permanent.
Flash memory chips are both changeable and nonvolatile.
That makes flash useful for both memory and for
storage.
A final point – do not be confused by the term CDROM.
CD-ROM drives are storage devices, and have
nothing to do with ROM memory.
Sensors
gather input
from the
environment
Sensors
With conventional computers, people operate the
input devices – we type, speak into microphones,
scan images, and so forth.
Embedded computers also get input from sensors.
For example, the acceleration sensor in a tablet
computer or cell phone allows the program to
detect and respond to motion – it knows when the
device is moved or rotated.
The devices shown on the left are temperature
sensors.
They might be used by a computer that controls
heating and air conditioning.
There are many other types of sensor
Sensors are
input devices
and effectors
output
devices.
Effectors
Embedded computers typically get input from
sensors as well as people and they can control
devices.
This thermostat reads the desired temperature
from a dial rotated by a user.
It reads the current room temperature using a
temperature sensor.
And it turns the heater or air conditioner by
outputting a command to an effector.
Sensors are input devices from the environment
and effectors are output devices to the
environment.
The Internet
of things –
devices with
embedded
computers
are
increasingly
connected to
the Internet.
You may hear people speak of “the Internet of
things.”
The Internet of things
We interact with computers using our fingers,
eyes and voices – our senses.
Things interact using light, temperature and other
types of sensors.
More things – from building light and heat
controls to soil moisture detectors to location
trackers on migrating birds – are connected to the
Internet every day.
Summary
We saw that many special purpose devices have
computers embedded inside them.
Summary
CPU
Input
devices
Memory
system
Storage devices
(programs and data)
Output
Devices
They have the same functional components –
input and output devices, memory, storage and
CPU – as general purpose computers.
Embedded computers often get input from
sensors and send output to effectors that control
devices.
Programs are stored in non-volatile, read-only
memory on embedded computers.
Devices with embedded computers are
increasingly being connected to the Internet,
creating an Internet of things.
The Internet of things brings us new applications
and efficiency, but it also exposes us to risks from
program or machine errors or malware.
Self-study questions
1. Is an embedded computer more likely to keep its program in RAM or ROM? Explain.
2. What are the input, output and storage devices on a tablet computer?
3. What are the input, output and storage devices on a smart phone?
4. Are smart phones special purpose or general purpose computers?
5. What are the input, output devices of an ATM machine?
6. Where do ATM machines store information?
7. Where is the program of an ATM machine?
8. When you cook something in a microwave oven for one minute, what is the embedded computer
programmed to do when the time runs out?
9. We talked of sensors for measuring temperature and acceleration. What other type of sensors are available
for today’s computer systems?
10. Give an example of an effector that is controlled by an embedded computer.
11. What is some of the information your car can communicate using onStar or Ford Synch?
12. What are some privacy issues raised by automotive information systems?
Resources
New York Times article on ARM, the leading designer of chips for embedded systems:
http://www.nytimes.com/2010/09/20/technology/20arm.html?_r=1&th&emc=th
ARM Web site, with many examples of embedded applications and an overview of their product line:
http://www.arm.com/
Risks of embedded smart phones:
http://blogs.mcafee.com/enterprise/mobile/why-does-my-car-have-its-own-smartphone
The risk of software error in cars:
http://www.economist.com/blogs/babbage/2010/05/techview_cars_and_software_bugs
The use of embedded computers in cars:
http://spectrum.ieee.org/green-tech/advanced-cars/this-car-runs-on-code/0