2. 2
Topics
Introduction to Embedded systems
How embedded is different from PC
Design constraints in embedded software
Examples of Embedded applications
Software development cycle in embedded
applications
Architecture of embedded applications.
Development Guidelines
4. 4
Introduction of Embedded system
An embedded system is a combination of computer hardware and
software accomplished with additional mechanical or other parts designed
to perform a
Embedded software is used in real life like
cell phone, pager, digital camera, portable video games, Calculators,
oven, washing machine etc.
: :Embedded systems often must cost just a few
dollars, must be sized to fit on a single chip, must perform fast enough to
process data in real-time, and must consume minimum power to extend
battery life. High user expectations in terms of performance
Specific Function
In every electronic device
Limited Resources
5. 5
Connect via peripherals
Embedded Systems talk with the outside world via peripherals,
such as:
Serial Communication Interfaces (SCI): RS-232, RS-422, RS-485
etc.
Universal Serial Bus (USB)
Multi Media Cards (SD Cards, Compact Flash etc.)
Networks: Ethernet, Lon Works, etc.
Analog to Digital/Digital to Analog (ADC/DAC)
6. Examples In Your Daily Life
…wake up …
…have breakfast …
…set home safety system …
…get into your car …
…on your way to your office…
6
9. 9
9
A “short list” of embedded systems
And the list goes on and on
Anti-lock brakes
Auto-focus cameras
Automatic teller machines
Automatic toll systems
Automatic transmission
Avionic systems
Battery chargers
Camcorders
Cell phones
Cell-phone base stations
Cordless phones
Cruise control
Curbside check-in systems
Digital cameras
Disk drives
Electronic card readers
Electronic instruments
Electronic toys/games
Factory control
Fax machines
Fingerprint identifiers
Home security systems
Life-support systems
Medical testing systems
Modems
MPEG decoders
Network cards
Network switches/routers
On-board navigation
Pagers
Photocopiers
Point-of-sale systems
Portable video games
Printers
Satellite phones
Scanners
Smart ovens/dishwashers
Speech recognizers
Stereo systems
Teleconferencing systems
Televisions
Temperature controllers
Theft tracking systems
TV set-top boxes
VCR’s, DVD players
Video game consoles
Video phones
Washers and dryers
11. 11
Difference - Embedded and PC
An embedded system have defined process and function whereas PC
is generic
Computer system can be manufactured with general requirement and the
manufacturer does not know what the customer will do, while embedded
system is Application Specific .
Numerous embedded system make up the computer
Tightly constrained: Embedded system design is tightly constraint.
Important factors to be considered are as cost, size, performance, and
power.
Reactive and real-time:
Continually reacts to changes in the system’s environment.
Must compute certain results in real-time without delay
12. Difference - Embedded and PC App- Coding
12
Embedded
Closer to the Hardware
Use native data types
Fewer System Resources
No Operating System
More efficient algorithms
Higher frequency = higher
power
PC Application
Abstracted Hardware
Plenty of Resources
Has an Operating System
13. Embedded vs PC App - Testing
Embedded
Debugging is very difficult
Emulators or simulators are
required at the time of
development
Usually a simple interface
Often involves extra hardware
PC Application
Usually simple to get a basic
debug output
Can be very sophisticated
testing
15. Design Challenges
15
Cost Unit Cost- Cost of manufacturing each unit
NON recurring Engg Cost: Monetary cost of designing the system
The physical space required by the system and measured in bytes for
software and gates for hardware.
Execution cost
The amount of power consumed which determines life time of battery.
Maximum Source of power : Antennas – Bluetooth, Wi-Fi, RF .
Digital displays
Time-to market constraint. Hardware and software development goes in
parallel
Missing this window – significant loss
Size
Performance
Power
Time Line
Flexiblity Change functionality without heavy NRE cost. Code should be
maintainable
17. Examples of embedded system
17
Car cruise
controllers reacts
to brake sensor
and speed
It Compute acceleration
and deceleration System
Failure
Delayed
computation
18. Mobile evolution – impact on design matrices
18
1980 analog cellular technology
Digital Mobile
Communication 1990
Wide Band Mobile
Communication 2000
Broadband Mobile
Communication 2010
Factors Affected
Cost
Design Complexity
Size
Performance
Power Consumption
19. Digital camera- An embedded system example
19
Microcontroller
CCD preprocessor Pixel coprocessor
A2D
D2A
JPEG codec
DMA controller
Memory controller ISA bus interface UART LCD ctrl
Display ctrl
Multiplier/Accum
Digital camera chip
lens
CCD
20. Time to Market- Design challenge
20
Revenues($)
Time (months)
Market window:
Period during which the product would have highest sales
Average time-to-market constraint is about 8 months. Delays can be costly.
21. Design Challenge
21
After decision of mass production of embedded system and a small
bug found at that time may be very expensive. Even a 1 day delay can
cost equivalent ……… Any Guesses??
28. Guidelines for embedded application
development
Power:
Optimal Power usage
Transferring data on Air
Reset Device
Design for the restoration of configuration
28
Memory Guidelines
Data Type
Life time of variable
Memory allocation on heap or stack. Memory should be freed
if not required
Stateless components
Logging and Instrumentation
User Interface
Simple UI
Hour glass as visual indicator for blocking operation
Resolution and LCD size
Design for usability by supporting for touch, stylus driven, 5-
way
Do not update ui frequently
29. Key rules for best coding
29
Maintainability Reliability Efficiency
32. 32
Coding standards
Readability of code
Size of Function
Variable naming
Code Commenting
Long methods
Private, public or local variable naming rule
Formatting and indentation
Complexity of code
Multiple return statement
Nested loop or conditions
Uninitialized variables
Duplicate code prone to errors
Avoid Hard Coding
Use of enum to indicate discrete values
Multilingual support
Reusable code or shared libraries
33. Sample code
33
// This class provides the functionality
// of adding numbers
#include <iostream>
using namespace std;
class Adder{
public:
// constructor
Adder(int i = 0)
{
total = i;
}
// interface to outside world
// Adds a number and calculates
total
void addNum(int number)
{
total += number;
}
// interface to outside world
//get sum total result
int getTotal()
{
return total;
};
private:
// hidden data from outside world
int total;
};
int main( )
{
Adder a;
a.addNum(10);
a.addNum(20);
a.addNum(30);
cout << "Total " << a.getTotal()
<<endl;
return 0;
}
34. Which one is better
bool MyApplication::ReportGenerator::
GenerateReport()
{
bool returnValue = false;
if (isAdmin() &&
isConditionOne() &&
isConditionTwo() &&
isConditionThree())
{ returnValue = generateReport(); }
return returnValue;
}
34
bool
MyApplication::ReportGenerator::GenerateReport(
)
{ if ( ! isAdmin () ) return false ;
if ( ! isConditionOne () ) return false ;
if ( ! isConditionTwo () ) return false ;
if ( ! isConditionThree() ) return false ;
return generateReport() ;
}
35. Sample Code
35
function do_stuff() {
// …
if (is_writable($folder)) {
if ($fp =
fopen($file_path,'w')) {
if ($stuff =
get_some_stuff()) {
if
(fwrite($fp,$stuff)) {
// ...
} else {
return false;
}
} else {
return false;
}
} else {
return
false;
}
} else {
return false;
}
}
function do_stuff() {
// ...
if (!is_writable($folder)) {
return false;
}
if (!$fp = fopen($file_path,'w')) {
return false;
}
if (!$stuff = get_some_stuff()) {
return false;
}
if (fwrite($fp,$stuff)) {
// ...
} else {
return false;
}
}
The time-to market constraint has become especially demanding. Introducing an embedded system to the marketplace early can make a big difference in the system’s profitability, since market time-windows for products are becoming quite short, often measured in months. Hardware and software development goes in parallelMissing this window (meaning the product begins being sold further to the right on the time scale) can mean significantloss in sales.
The design measures typically compete with one another: improving one often leads to a degradation in another. For example, if we reduce an implementation’s size, its performance may suffer. Designer should comfortable with a variety of hardware and software implementation technologies, and must be able to migrate from one technology to another, in order to find the best implementation for a given application and constraints. Also he must be software and hardware expert .
A car's cruise controller continually monitors and reacts to speed and brake sensors. It must compute acceleration or decelerations amounts repeatedly within a limited time; a delayed computation result could result in a failure to maintain control of the car. In contrast, a desktop system typically focuses on computations, with relatively infrequent (from the computer’s perspective) reactions to input devices. In addition, a delay in those computations, while perhaps inconvenient to the computer user, typically does not result in a system failure.
Single-functioned -- always a digital cameraTightly-constrained -- Low cost, low power, small, fastReactive and real-time -- only to a small extentCCD:complete mixed-signal processing IC for digital cameras,A2D- analog to digital conversionCCD imager output signal in a video camera, a digital still camera, security camera, or similar applicationsPixel Processor: The pixel processor receives raw data from the pixel chips and formats it for useCodec: A codec is a device or computer program capable of encoding or decoding a digital data stream or signal.A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripheralsAn accumulator is a register for short-term, intermediate storage of arithmetic and ... and manipulation of imagery, GPS, satellite photography and historical data, ...
Product specifications are driven by market mainly and also change very frequently like camera or mobile. Development of Hardware and software goes in parallel which is a major challenge.
Stateless components are preferred when scalability or performance are important. Design the components to accept all the needed values as input parameters instead of relying upon object properties when calling methods. Doing so eliminates the need to preserve object state between method calls. When it is necessary to maintain state, consider using alternative methods, such as maintaining state in a database.limited memory available on small device- logging and instrumentation should be limited Take into account the various screen sizes and resolutions of your target devices when designing your application UIDesign devices so that parts can be powered off when not in use.Transferring data on Airuse batch burst and shut down communication when not needed
Reliability measures the level of risk and the likelihood of potential application failures. It also measures the defects injected due to modifications made to the softwareMaintainability- how muchadaptle to change and readable and easy to understandEffecience is linked with performance