1. An Introduction to Embedded Software Architecture and Design
Class 3: Understanding Embedded Software Architectures
December 3, 2014 Jacob Beningo, CSDP

2. Course Overview Introduction to Embedded Software Architecture
Software Architecture using UML
Understanding Embedded Software Architectures
From Architecture to Implementation
Software Architecture of a UAV and Review

3. Session Overview An Example Problem Embedded Software Architecture
Importance of time
Common patterns
Boot-loader Architecture Design
Peeling the onion
Uml diagrams
A few architecture tips

4. Embedded Software Architectures
Embedded Systems
Many different flavors
Each industry has their own best practices
Software architectures deal with three different domain types

5. Embedded Software Architectures
Hard real-time systems
Definitive deterministic response to an event
Known that response is always within a give time
Soft real-time systems
Response to an event requires an average time
Application systems
Timing is not a consideration in the development of the system

6. Embedded Software Architectures
Importance of Time
System catastrophes
Unexpected behavior
How should the architecture handle time?
Move time-dependent requirements into the hardware
Use interrupts to ensure the hard real-time needs
Scheduler can handle the soft real-time needs
Everything else is de-coupled!

7. Embedded Software Architectures
Common Embedded Software Patterns
Polling
Interrupt triggered (blocking)
Interrupt triggered (non-blocking)
Event driven
RTOS
Energy Aware

8. Boot-loader Architecture….
Remote firmware updates
System requires periodic firmware updates in the field without the use of specialized hardware
Must blink an led in this mode
Seamless ability to switch between app and update mode
System requires the ability to be updated via UART
simulates radio connectivity

9. Boot-loader Architecture Design
Requirements
What does the system do?
How does it interact with
the user?
the environment?
Real-time Requirements
The system “shall” …..
Precisely define what the system not how!
Verifiable and testable

10. Boot-loader Architecture Design
Create a high level system architecture

11. Boot-loader Architecture Design
High level software architecture

12. Boot-loader Architecture Design
Create a use case diagram

13. Boot-loader Architecture Design
Create component diagram
Component Lists
Low level Driver components
Inputs and Outputs
Timers, PWM, etc
Configuration components
What needs configuring?
Application components
Sensor Interfaces
Real-world interfaces
Timer
Digital I/O
PWM
ADC
Sensor Filtering
Motor

14. Boot-loader Architecture Design
Boot-loader Component Diagram

15. Boot-loader Architecture Design
Boot-loader Detailed Component Diagram

16. Boot-loader Architecture Design
Statechart design

17. Boot-loader Architecture Design
Sequence Diagram
Time or sequence critical architecture

18. A few architecture tips
Where to put different functionality
Real-time requirements into hardware as much as possible
Create layers and abstractions
Highest layers should be portable and easily changed to meet application needs
Architecture itself should not be easily changed or changed often

19. A few architecture tips
Planning for change
Expect requirements to change!
Rarely are they set in stone
Plan for diagnostics
How are system states, errors, etc going to be logged?
Critical to system debugging
Plan for testing
Testing framework?

20. Additional Resources Download Course Material for Edraw UML Templates
Updated C Doxygen Templates
Misc Papers and Websites for further reading
From under
- Blog and Articles > Software Techniques > CEC Software Architecture Materials

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