Announcements
 Lab hours
 Wednesday 4:00-5:30pm, Friday 1:00-2:30pm
• Min Kao 228
• Works fine for all but three students
 Your presence is not required
 We encourage you to use your own computer for
labs/projects on your own time
 Lab is only for those students who have no computers
 TA will be in the lab to help your programming problems
and check off your lab assignments
 Lab will open after the first lab assignment is announced
• The first week of September (next Wednesday)
ECE 455/555 Embedded System Design
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ECE 455/555
Embedded System Design
Design Methodology - II
Wei Gao
Fall 2015
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Design Challenges
 Non-functional constraints
 How do we meet deadlines?
• Faster hardware or better software?
 How do we minimize power?
• Turn off unnecessary logic? Reduce memory accesses? Slow down
CPU?
 Cost considerations
 Trade-offs among constraints
 Optimization & analysis are important!
 Will be covered in this course
ECE 455/555 Embedded System Design
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Design Methodologies
requirements
Top-down design
specification
architecture
component
design
Bottom-up design
system
integration
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Requirements
 Plain language description of what the user wants
and expects to get.
 May be developed in several ways:
 Talking directly to customers;
 Providing prototypes to users for comment.
 Functional vs. non-functional requirements
 Functional: output as a function of input
 Non-functional: timing constraints, power consumption,
size, weight, etc.
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Requirements Form
name
purpose
inputs
outputs
functions
performance
manufacturing cost
power
physical size/weight
ECE 455/555 Embedded System Design
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Example: GPS Moving Map Requirements
 Non-technical: Where I am?
 Technical: Obtains position from GPS, paints map
from local database.
Morrell Road
I-40
lat: 40 13 lon: 32 19
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GPS Moving Map Requirements
 Functionality
 For car driving use, not for airplanes or boats
 Show major roads and landmarks.
 User interface
 At least 400 x 600 pixel screen.
 Three buttons max.
 Pop-up menu.
 Performance
 No more than 1 sec power-up.
 Lock onto GPS within 15 seconds.
 Update location every 0.25 sec.
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GPS Moving Map Requirements
 Cost: street price no more than $100
 Physical size/weight: Should fit in hand.
 Power consumption: Should run for at least 8 hours
on four AA batteries.
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GPS Map Requirements From
name
purpose
inputs
outputs
functions
performance
manufacturing cost
power
physical size/weight
GPS moving map
consumer-grade
moving map for driving
power button, two
control buttons
back-lit LCD 400 X 600
5-receiver GPS; three
resolutions; displays
current lat/lon
updates screen within
0.25 sec of movement
$100 cost-of-goodssold
100 mW
no more than 2: X 6:,
12 oz.
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Specification
 More precise description of the system:
 should not imply a particular architecture;
 provides input to the architecture design process.
 May include functional and non-functional elements.
 UML: Unified Modeling Language
 Not required in this course
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GPS Specification
 Should include:
 what is received from GPS;
 map data, format;
 user interface, menu items;
 operations required to satisfy user requests;
 background operations needed to keep the
system running
• Event-driven or periodic?.
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Architecture Design
 What major components can satisfy the
specifications?
 Hardware components:
 CPUs, memory, GPS receiver, etc.
 Software components:
 Topographical database, access functions, etc.
 Must take into account functional and non-functional
specifications.
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GPS Moving Map Block Diagram
GPS
receiver
search
engine
database
renderer
display
user
interface
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GPS Moving Map Hardware Architecture
display
frame
buffer
CPU
GPS
receiver
memory
panel I/O
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GPS Moving Map Software Architecture
position
database
search
renderer
user
interface
timer
ECE 455/555 Embedded System Design
pixels
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Designing Hardware and Software
Components
 Must spend time architecting the system before you
start coding.
 Components maybe
 ready-made
 modified from existing designs
 designed from scratch
 Components in an embedded system will be covered
in following classes
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System Integration
 Put together the components.
 Many bugs appear only at this stage.
 Individual components should be tested first!
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Summary
 Characteristics of embedded systems
 Non-functional requirements: real-time, low-power, low-cost
 Embedded systems pose many design challenges:





Design time
Deadlines
Power
Cost
…
 Design methodologies help us manage the design process.
 Top-down vs. bottom-up
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Reading
 Textbook: Sec 1.1, 1.2, 1.3
 Optional (but interesting!) reading on web page
 N. Tredennick and B. Shimamoto, Go Reconfigure, IEEE Spectrum,
40(12): 36-40, 2003.
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