Introduction to Embedded Systems

1. Introduction to Embedded Systems

2. Introduction
From hardware specific designs to general platforms

3. Systems Around Us
Devices interact with their environment
 Receiving Inputs (Sensors that capture changes/events in the environment)
 Processing (inputs, current and/or past states)
 Sending Outputs (responding to environment through actuators)
Processing decides what response to send for given input
 Can be electronic, mechanical or other types
 Should be able to understand and interpret inputs
 Should be able to control behavior of outputs
Input Output
Process

4. Electronic Systems
Use sensors (transducers) to convert a physical
phenomenon into an electric (voltage, current) signal and
capture as inputs
 Switches
 Keyboards
 Transducers (encoders, pressure sensors, gyroscopes,
voltage/current sensors etc.)
Process inputs electrically
 Work according to a predefined algorithm or a process
 Generate voltages and currents that are required by the
actuators to create necessary output in the required form

5. Analog Systems
Analog signals are prone to noise and variations (line
resistances etc.)
Processing is built into the design – non-flexible design
May use non-solid state devices
Difficult to design, manufacture and expensive to
maintain
Analog
Sensors
Analog
Actuators
Analog
Processing
Real
World
Real
World

6. Problems with Analog Systems
Analog signals are prone to noise and interference
 Simple loose connection or a long exposed cable may change
the signal travelling through that
• A sensor may output a signal with 0.7V, but by the time it reach
the processing circuit, voltage may have dropped down to 0.65V
or may be corrupted with a random noise with 0.9V peak to
peak.
 Low error margins – need precision components and designs
Discrete signals can help in solving these problems
 Higher error margins
 Deterministic values – can recover from corrupted signals

7. Digital Systems
Natural world is Analog – often need to convert to digital and back
Digital signals are more immune to noise and other interferences
Processing based on Boolean algebra (digital logic)
Design more flexible than analog ones – more unified design
approach
Design is rigid but more flexible than analog designs
Easier to design, manufacture and less expensive to maintain
Real
World
AtoD
conv.
DtoA
conv.
Digital
Processing
Real
World
Analog
Sensors
Analog
Actuator

8. Designing Systems (Digital or Analog)
Designing and building an electronic system is not easy
 Need to understand the problem domain
 Decide what inputs to capture and what outputs to produce
 Decide how to derive output from inputs
 Design the circuit addressing various issues such as noise,
signal interference, power consumption etc.
 Design the printed circuit board and other accessories
 Manufacture and package
 Market
Continue support and maintenance over a period of time
 Each design is unique – a change in a single component may
require entire design to be re-done
 Difficult and expensive

9. Problem
 Difficulty in climbing steps

10. More Flexible Designs
Most systems have common input/output features but differ on how
they are processed
 Can we separate input/output from processing?
 Can we make processing to be flexible and independent from the
hardware design?
 Can we change processing without changing hardware design?
 Can we have the same processing but using different hardware setup?
Solution came from a different industry
 A textile looms producing different patterns using the same machine
 Provided initial steps towards automation
 See next slide for a video

11. Joseph Jacquard’s Power Loom
https://www.youtube.com/watch?v=f1Zzj9ZBY
mQ

12. ExtendingJosephJacquard’sidea- MicroprocessorBased
Systems

13. What is an Embedded System..?
Many Definitions
A microprocessor-based system
Built to control function(s)
Not designed to be programmed by the end
user
User can make choices/select options but cant
change software
What about a PC?

14. Microprocessor Based Systems - Benefits
Use of common components – savings in cost
 Majority of hardware components and architecture will
remain common across multiple devices, versions or
configurations
• Support standardization and component re-usability
• Can be built using readily available, standard components
• Trusted platforms, more tools and support available
 Software is easier to maintain compared to hardware
designs
Software allows more complex logic/algorithms at
lesser cost
 Better control and smooth operations
 More flexible
 More functional

15. Example – Railway Signaling Systems

16. Signal Point Control Module
Each control module handles one signal point
 Backplane bus provide a common communication
path to all signal points and their respective control
modules
 Each control module is a “hot-pluggable” card that has
a standard interface
• Receive inputs from track sensors.
• Generate outputs that control signal lights and track
changing points.
 Mapping from inputs to output is a unique for each
signal point
Hardware/Software Designs
 Hardware based approach
• Control algorithm is built into the hardware logic. Each
board becomes a custom built circuit for that signal point.
 Software based approach
 Algorithm is in software – different software modules
running on the same hardware platform

17. Hardware/Software Approach – Key Benefits
Hardware becomes standard across multiple modules
 Reduction of cost through large scale production
 Use readily available components
 More reliable components, designs and modules
 Less dependency on specific parts/architectures
Facilitates maintainability
 Place hardware in a “Black-box” and build all operational
logic in to “software algorithms”
 “Processing logic” is independent of hardware design
 Maintenance and upgrades through software
 Support complex logic on the same platform

18. Hardware/SoftwareApproach – EconomicBenefits
Economics of standardization
 Sales cost and profit margin of a product is not limited to material &
manufacturing costs
 Sales price usually consist of
• Material cost
• Manufacturing (plant & labor)
• Marketing, sales costs and profit margin
• NRE cost per unit
• Inventory and souring cost
• Spares, warranty and maintenance
 Use of standard components and standardization of inventory can
help in reducing many of the above, especially those in red color.

19. Hardware/SoftwareApproach – EconomicBenefits
Breakdown of world’s semiconductor production

20. Hardware/SoftwareApproach – Other Benefits
Shorter design/development time
 Reduction in time-to-prototype/time-to-market windows –
bring competitive advantage over others
Readily available resources
 Development tools, testing tools, developers and other
resources
Protection of intellectual property
 IP is included in the software – easier to protect against reverse
engineering
Flexible and re-usable designs
Easy maintenance and upgrades
 Mostly through software – even at end-users location or
through remote management

21. What led the (increasingly) widespread
use of HW/SW approach?
Replacement of discrete logic-based circuits
Providing functional upgrades
Providing easy maintenance upgrades
Improving mechanical performance
Protection of intellectual property
Replacement for analog circuits
Since integrated circuit design was (and still is) an expensive and time
consuming process, the ability to reuse the hardware design by
changing the software was a key breakthrough.

22. What led the widespread use of Hw/Sw
approach?
Replacement of discrete logic-based circuits
 Up to 1970, most control systems used integrated circuits
 First microprocessor was a programmable replacement for the calculator
chips
• Before that calculator functionality was based on logic chips
 Changes or improvements in any system required to develop new chips
• Creating new functions by analyzing the gate level logic and modifying it
• A very time consuming process
 The answer was to build a chip that had some form of programmable
capacity in it
 Why not build a chip that took data in process and send the results out?
 New products could be created by changing the program code

23. What led the widespread use of Hw/Sw
approach?
Providing functional upgrades
Ability to add/remove functionality from embedded
systems is very important
Much of the system’s functionality encapsulated in
the software
Changing/upgrading the system by changing
software
Hardware is kept the same
Reduced production cost
Upgrading is possible even remotely

24. What led the widespread use of Hw/Sw
approach?
Providing easy maintenance upgrades
Same mechanism in previous slide allows bugs to
be resolved through changing software
Reduces the expensive repairs that involves
hardware modifications

25. What led the widespread use of Hw/Sw
approach?
Improving mechanical performance
 Finer degree of control is essential for any electromechanical system
 It can prevent excessive wear, provide better control, diagnostics and even
compensate for wear and tear
• E.g. An engine control system that acts on input like temperature, accelerator
pedal position and so on
• Configurable for different environments
 Third parties can boost performance by changing control software
• Can void manufacturer warranty
• Can cause shorter lifespan
• Even infringe manufacturer's intellectual property rights
See in next slide about this

26. What led the widespread use of Hw/Sw
approach?
Protection of intellectual property
A completely hardware based design is easy to
reverse engineer and reproduce
• Identify the chips and connections and understand
the design
But software is not that easy to copy
Can be burnt into the on-chip memory –
effectively impossible to access

27. What led the widespread use of Hw/Sw
approach?
Replacement for analog circuits
Analog processing is simpler while digital
processing is more complex
Digital processing does not suffer from
component ageing/drift
They have high noise immunity
The ability to dynamically modify the coefficients

28. Hardware/Software Approach – Limitations
Performance
 Serial processing, only one micro step at a time
 Execution overheads
 Only once task (SISD) at any given time
Resource utilization
 Small systems may not need all resources available in the
processor
 Many resources may remain un-used
Efficiency
 Hardware design may be sub-optimal for a given task
 Higher power consumption–especially by unused resources
Security risks
 Some one could modify the software ?
 Cost
 May not be cost effective when large quantities are needed

29. In spite of theselimitations – Hw/Sw based designs have
invaded the consumerelectronicmarket
..and the list goes on and on.

30. Inside the embedded system
Processor
Memory
Peripherals
Software
Algorithms

31. Inside the embedded system
Processor
 Can it provide the processing power needed by the system?
• Most frequently, tasks are underestimated in
size/complexity
• Benchmarks do not represent real loads
• In simulations, execution takes place out of cache memory
but real programs do not fit the cache
• Software overheads for high level languages, operating
systems, interrupts
• Cost
System cost, not the processor in isolation
• Power consumption
• Software tools and component availability

32. Inside the embedded system
Memory
 Consumption is heavily influenced by the software design
 Software design is also influenced by the memory available
 Provides storage for the software
• Non-volatile memory
• On-chip ROM or EPROM
• Can store full software or initiation routine (bootstrap program)
 Provides storage for the data
• Program variables, intermediate results, status information
• RAM is volatile, faster and expensive

33. Inside the embedded system
 Peripherals
 Inputs/Outputs
 Sensors, actuators, displays, other signals
 E.g. motor controller  given input of current speed, and power, it produces PWM signal hence rotation
displaying the speed
 Binary outputs
 Simple external pins whose logic sate can be either 1 or 0
 Can be grouped in to parallel ports
 Serial outputs
 Uses one or two pins in serial mode
 Les complex to connect but complicated to program
• Parallel port looks very similar to a memory location
• A serial port has to have data loaded to a register and needs a start command at least

34. Inside the embedded system
Peripherals (contd.)
Analog values
Processors operate in digital domain
Natural world tends to orientate to analog values
Interfacing is necessary
Displays
Time derived outputs
Timers and counters

35. Inside the embedded system
Software
Initialization and configuration
Operating system/run-time environment
Application software
Error handling
Debug and maintenance support

36. Inside the embedded system
Algorithms
Key constituents of the software that makes an
embedded system works the way it does
Defining and implementing the correct algorithm
is critical
Processing power needed, speed, accuracy

37. In class
 State the characteristics of an Embedded
System.
 What are the challenges you face when
solving a problem implementing an Embedded
System?
 What are the components you would find
inside an ES?
 State at least two benefits and limitations of
using a hardware/software approach.