Emerging low power, embedded, wireless sensor devices are useful for wide range of applications, yet have very limited processing, storage and especially energy resources. Thus a key design challenge is to support application-specific optimizations in a highly flexible manner.
This paper deals with Embedded Systems in which the main emphasis is made on its architecture, characteristics, real-time systems, design and typical hardware and software, how it is differentiated from a Personal Computers, types of Embedded Systems, the products made with Embedded Systems, Input/Output of Embedded Systems, problems while dealing with Embedded Systems and its applications.
- Basics Concepts
- Embedded Systems
- What is an Embedded System?
- Key Differences with Personal Computers
- What made Embedded Systems possible?
- Types of Embedded Software Architecture
- Key Terminologies
- Common Uses
4. Sensors and Actuators
- I/O of Embedded System
- Examples of Embedded Systems
- Applications of Embedded Systems
- Future Uses
The most important industry of our days, Data Communication, is based on Embedded Systems.
q Embedded Software is not software for small computers
q It executes on machines that are not computers (cars, airplanes, telephones, audio equipment, robots, security systems…)
q Its principal role is not the transformation of data but rather the interaction with the physical world
q Since it interacts with the physical world must acquire some properties of the physical world. It takes time. It consumes power. It does not terminate until it fails
q Def1: to fix (something) firmly and deeply
q Def2: to enclose closely in a surrounding mass
q Implicitly a controlling system
What is an Embedded System?
"An embedded system is a special purpose computer system built in to a larger device. An embedded system is typically required to meet very different requirements than a general purpose personal computer.
An embedded system is a computer system contained within some larger device or product with the intent purpose of providing monitoring and control services to that device.
Convenience:-It makes the equipment more useful.
Cost: - Control functions have been handled mechanically, but an embedded computer system is cheaper and more reliable.
Embedded systems are a part of another system that must respond to event in the real world. Hence time inside the program is tied to time in the real world.
A modern car is more as "a computer system" than a personal computer in the sense that tens of microprocessors are controlling different functions of it. Also the most important industry of our days, Data Communication, is based on Embedded Systems.
Types of Real-Time Embedded Systems:
Hard:-Where not meeting a deadline failure.
Soft:-Where deadline can be missed and the system may still work.
Slow:-The system will have to respond with in seconds.
Fast:-The system will have to respond with in a second (mille or microsecond).
Two major areas of differences are cost and power consumption. Since Embedded Systems are produced in the ten thousands to millions of units range, reducing cost is a major concern. Embedded Systems often use a (relatively) slow processor and small memory size
1. Application and Domain Specific.
2. Reactive and Real-time.
3. Distributed. 4. Heterogeneus.
5. Operate in harsh environments.
6. Must meet high integrity quality attribute requirements.
7. Small Size and Weight. 8. Power concerns.
Embedded systems have several common characteristics that distinguished such systems from other computing systems.
An embedded system usually executes a specific program repeatedly for example, a pager is always a pager in contrast, a desktop system executes a variety of programs like spreadsheets, word processors and video games with new programs added frequently of course there are some exceptions. One case is where an embedded system’s program is updated with a newer program version for example; some cell phones can be updated in such a manner.
All computing systems have constraints on design metrics, but those on Embedded Systems can be especially tight. A design metric is a measure of an implementation features such as cost, size, performance and power. Embedded Systems must be fit on a single chip, must perform fast enough to process data in real time.
Reactive and Real-Time:
Many Embedded Systems must continually react to changes in the systems environment and must compute certain results in real time without delay.
KEY DIFFERENCES WITH PC’s:
React to external events that may be particularly rapid.
- Elevator on sky-scrapper at 7:45 am or 4:55 pm.
- Missile flying at low altitude over a mountainous area.
Must handle unusual events
- A user blocking an elevator door, power blackout, memory failure.
Task request with deadlines.
What made embedded systems possible:
1971: Intel 4004, first microprocessor (4 bits), initially for a calculator.
1981: IBM chooses Intel 8088 for the first PC.
Microprocessors get so cheap that microprocessor-based control system become rule.
Only limit: Processing time.
Types of embedded software architecture:
Ø THE CONTROL LOOP
Ø NON PREEMPTIVE MULTITASKING
Ø PREEMPTIVE TIMERS
Ø PREEMPTIVE TASKS
Ø OFFICE-STYLE OPERATING SYSTEM
Ø EXOTIC CUSTOM OPERATING SYSTEMS
embedded systems key technologies:
– A manner of accomplishing a task, especially using technical processes, methods, or knowledge
- Three key technologies for embedded systems
-- Processor technology
– IC technology
– Design technology
– Used to determine the state of some environment using input sensors.
– Used to impact the state of some environment using output actuators.
sensors and actuators:
– A device that responds to an environmental event by sending a resulting message for measurement or operating a control purposes
– A mechanical or electrical device for moving or controlling something
- Processing of physical data starts with capturing this data.
- Sensors can be designed for virtually every physical and
- chemical quantity
- Including weight, velocity, acceleration, electrical current, voltage, temperatures etc.
- Chemical compounds.
- Many physical effects used for constructing sensors.
- law of induction (generation of voltages in an electric field),
- Light-electric effects.
- Huge amount of sensors designed in recent years.
Acceleration Sensor Biometrical Sensor
- Rain sensors for wiper control
(“Sensors multiply like rabbits“ [IIT automotive])
- Pressure sensors
- Proximity sensors
- Engine control sensors
- Hall effect sensors
I/O of embedded systems:
- Application dependent: Switches, Sensors, Hexadecimal keyboard, LCD, basic key pads, Communication cards, LED's.
- Rarely: Monitor hard drive, secondary storage, mouse, keyboard and printer.
Typical hardware and software:
2. Memory Size.
3. Bus Width.
1. No disk drive on most Embedded Systems.
2. Require special memory to serve two purposes:
3. Store program and store data.
What Embedded Systems don't have (Hard ware free):-
1. Keyboard. 2. Monitor.
3. Disk Drive 4.CD Drive
5. Speakers 6.Microphones.
Real Time Operating Systems (with deadline scheduling) :-
Today this feature of the Web the ability to access downloadable multimedia files is seen as problematic. Recent advances in computing technology, compression technology, high bandwidth storage devices, and high-speed networks have made it feasible to provide real-time multimedia services over the Internet. Real-time multimedia, as the name implies, has timing constraints. Real-time transport of live video or stored video is the predominant part of real-time multimedia.
RTOS is the operating system shields the computer hardware from all the other software. The operating system offers various services related to the essential resources, such as the CPU, main memory, storage, and all input and output devices.
Video streaming is an important component of many internet multimedia applications. There are six key areas of streaming video, namely, video compression, application-layer QoS control, continuous media distribution services, streaming servers, media synchronization mechanisms, and protocols for streaming media.
Examples of embedded systems:
Ø disk drives
Ø handheld calculators
Ø household appliances, including microwave ovens, washing machines, television sets, DVD Players/Recorders
Applications of embedded systems:
v Digital Thermometer
v Bike Speedometer
v TV and Video
v House Alarms
v Car engine management system
v Antilock brakes
v Robot Controller
v Process Controller
v Guided Missiles
v Fire by Wire
v Space Station
v Air Traffic Control
v Embedded Systems can be applicable in a wide variety of fields such as Communications, Air Force, Navy, Industries, Military, Home applications, etc…
v Military:-Smart soldier, Battle field of the future, etc.
v Stepper motor control
v Keypad controllers
v Wireless communications
v Analog-to-Digital converters
v Intelligent highways
v Smart materials
v Drive by wire
v Medical: Implants, Monitoring etc.
v Next Generation communications: 3G wireless, etc.
v Infrastructure management: Energy, Water, etc.
v Hand Held Devices.
v Homeland security: Identification, chemical and biological sensors.
v Smart spaces: Sensor networks, embedded audio and video et
Stepper motor control:-
A stepper motor is an electric motor that rotates a fixed number of degrees when ever we apply a step signal. Stepper motors are common in Embedded Systems with moving parts, such as disk drives, printers, photo copy and fax machines, robots, camcorders and VCR's.
§ Embedded Computing will provide more uses in the future in the fields of Smart spaces: sensor networks, embedded audio and video; Entertainment: Impressive environments, real time synthesis and reaction, etc.
§ Operating system and application functions are often combined in the same program in Embedded Systems. The only obvious strategy was to put more of the system onto the chip. So reducing external components and cost and increasing reliability.
§ Embedded Systems follow a trend related to IC's i.e.: IC transistor capacity will double roughly for every 18 to 24 months. This trend was predicted by Intel co-founder Gordon Moore. The trend is therefore known as Moore's Law.
· Embedded Software Primer -By David E.Simon
· Design of Embedded Systems by Sangiovni Vincen