Describes about embedded systems and breif on good coding practices.

1. Embedded system and
Development
Rajani Bhandari
Senior Project Manager
HCL Technologies

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

3. 3
Introduction to Embedded systems

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

7. Examples In Your Daily Life
(cont’)
 …in Your office…
7

8. Examples In Your Daily Life
(cont’)
 …Back Home …
8

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

10. 10
Embedded Vs PC

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

14. 14
Design challenges

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

16. Design Metrics
16
SizePerformance
Power
NRE
cost
Improving one often leads to a degradation in another

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??

22. 22
Software Development Life cycle

23. Embedded system Life Cycle
23
Development of Hardware and software goes in parallel which is a major
challenge.

24. 24
Architecture of embedded application

25. 25
Architecture of embedded system
Application Software
Operating System
Hardware

26. Hardware architecture
26

27. 27
Development Guidelines

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

30. Maintenance problems
 Unstructured code
 Insufficient domain knowledge
 Insufficient documentation
30

31. Efficiency
 Optimal Utilization of Resources
 Design and architecture of software
 Memory management
31

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;
}
}

36. 36
Quality software On-time to bring customer
Delight



Good Coding and Design brings >>>

37. Questions ??
37

38. Thanks!!
38