Chapter 4: Embedded Systems Flashcards
What is the motivation for embedded systems?
- pervasive computing means connected computational devices become interwoven with things in our everyday life
- computation unit should be unnoticed by users
- > They need to be small and embedded and may not have classical input / output possibilities
- they got cheaper and increased in power
The definition of embedded systems
- Is a computer system with dedicated function that is physically embedded within a larger physical object
- Everything that includes a microprocessor (but not a general purpose computer)
- It is optimized for specific tasks and scenarios (huge variety)
Give some examples for embedded systems
Peripherals (small and simple): Key Finder
Transportation (large and complex): Car computer
Robotics (reliable): Moon car
Medical Devices(safety critical): pace maker
- Routers
- GPS receivers
- MP3 Players
- Fridge
What are the requirements on an embedded system?
- Depends on the physical host object in which it is embedded
- Price, weight, form factor (state of the art i9 too expensive?). We need hardware customly build for the application domain.
- Mobility (wireless communication / charging possible?)
- Accessibility (deeply embedded -> hard to repair)
- Human-Computer-Interaction (may not have a screen or only small one)
- Expected Lifetime (possible to run on battery for years)
How is an embedded system operated in the real world context?
- Host object & embedded system are located in a specific physical context
- System is influenced by the context and may influence it in return
Reallife context sets very hard requirements on the system:
- Real-time
- Safety
- Security
- Flexibility
What sources of restricitons exist for embedded systems
- Restrictions by the host object
- Restrictions by the physical world (very hard requirements)
What are the challenges that come along with the characteristic of “dedicated function” in an embedded system ?
- It is tailored and optimized for an exact task
- This means that the system is much more restricted with respect to compute power, memory, energy
- Need to develop / adapt SW & Hardware for each new device
What kind of design approach exist for embedded system?
- Classical Approach
- Modern Approach
Explain the classical approach to design an embedded system.
- Tailored devices
- Specialised engineers only doing this
- Design new HW; SW for each application
Explain the modern approach to design an embedded system.
- Generic devices adapted as needed
- Wider developer base
- Focus on SW design, only basic HW design
What is the difference between developing desktop apps and embedded systems ?
- Many target platforms (HW/OS)
- Other programming languages
- Other programming abstractions and APIs
- Other development tools (cross-compilers)
- Different development process
Name three Embedded OS
- Linux
- eCos
- LynxOS
Name the three most relevant languages for embedded system
1) Python
2) C++
3) C
What are the challenges for programming abstractions for embedded system development
- We may have restricted or no OS support
- Device drivers may be available as C library that need to be used in the application code directly
If we are lucky: Hardware Abstraction Layer available
Often: lower level programming with access to HW
What is the difference between a Desktop app and embedded system in terms of architecture
Desktop Components:
- Application Software
- Middle Layer
- OS
- Device Drivers
- Hardware
Embedded Components:
- Application Software
- Hardware
Desktop has a higher programming abstraction for application software!
What are the challenges of cross-platform development
- Software is developed on one platform (host system) but runs on another (target system)
What is the host system in regards to cross-platform development
- The system on which the embedded software is developed
What is the target system in regard to cross-platform development
- The embedded system that is under development
What is the cross compiler in regard to cross-platform development
- A compiler that runs on one type of processor architecture but produces code for a different type of processor architecture
What different hardware does an embedded system have
- Processing Unit (low computational power, highly specialized)
- Memory
- Internal on-chip memory (very fast, cache)
- Internal off-chip memory (not in circuit, slower, main memory)
- External memory (flash drives, removable)
- Communication
- Different I/O standards
- Low Power Networks
What is the challenge with inputs for embedded systems?
- User seldomly has a keyboard
- But we can measure physical state with sensors (many sensors exist)
- Modern sensor technology is main driving force for designing smart embedded systems
What is the challenge with outputs for embedded systems?
- Screens are often small or cumbersome
What is a typical output for embedded systems
- Actuators (Computer controls Output through a physical device) - can affect the real world
Digital Output: setting digital output PIN to HIGH
Analog output: applying voltage to analog output PIN
Name some sensors and actuators for a laundry machine
Sensors:
- Temperature
- Pressure
- Water level
Actuators (A device that can affect the real world):
- Motor
- LED
- Buzzer/Bell
What is an Information Appliance?
- Appliance (App) specialized in information (knowledge, graphics, sound)
- designed to perform a specific activity (music, photography)
- Ability to share information among themselves
What are the key characteristics of an information appliance?
- Limited purpose and functionality (to a specific task)
- May be not extensible or upgradeable
- Replacement expectation (User needs to replace)
- Perceived as less expensive
- No expectation of expert users
For those two points: Take functionality threshold into account!
- Perceived as less complicated to run and maintain
- Very easy to learn and use
What are thee Axioms for Information Appliances?
- Simplicity: easy to use as possible
- Flexibility: enables creativity
- Fun: when using it
What is the key when designing information appliances?
- You need to think about it as an appliance
- You don’t design a computer
- Customers do not want to use a computer
What are the design considerations for information appliances?
1) Account for the target domain
2) Dedicated user interfaces
3) Allocate functions appropriately
4) Simplify
5) Design for responsiveness
Which target domains exist for which you need to account for?
- Entertainment (long interactions, less structured interaction, not very directed tasks)
- Information Access and Communication (short interactions, structured interaction, directed tasks)
- Assistant Devices (similar to information access and communication)
What is an example for dedicated user interfaces?
- Leverage the different possibilities of a device for user interface
- Email Client on phone needs to be more compact / less information
- Email client on pad can show more information due to larger display
What is an example for a design failure?
- Allocating not enough space for buttons in touch-based apps
How can you allocate functions appropriately?
1) Frequency
- Functionalities that are used more often should be allocated to visible and accessible controls (e.g. Search Bar)
2) Importance
- Most important functionalities should be allocated to visible and accessible controls (installation / configuration)
Both aspects need to be considered separately
How can you simplify information appliances?
1) Functionality Threshold
2) Choice Reduction
Explain the functionality threshold in regard to the information appliance design
- The sweet spot between functionality and simplicity
- Device should be as simple as possible but also to have enough functionality to be of interest to user
- Too little functionality: appliance not appealing / useful
- Too much functionality: appliance too complicated
It can also change over time depending on users previous knowledge
How can you design an information appliance responsive?
- Interruptibility (don’t block the user but allow to interrupt activities naturally)
- Continuous Feedback (even if product is functioning normally, feedback on successful operations)
- On a pc users often expect to get feedback if something is not working
What are wearables?
- Computers attached to a humans body (specifically designed for mobile scenarios)
What are challenges for wearables
- Should not interfere with work
- No traditional I/O
- Not always online
- Ergonomics
What are the seven principles of Universal design for wearables
1) Equitable use
2) Flexibility in use
3) Simple and intuitive
4) Perceptible information
5) Tolerance for error
6) Low physical effort
7) Size and space for approach and use
What are the design approaches for wearables?
- Monolithic structure / design
- Central computing unit with peripherals
- applications with high performance requirements
- Distributed Wearables
- Task distribution amongst small specialized units
- for applications with high level of integration and flexibility
- Hybrid Wearable
- Combines benefits of the two approaches
How are modern wearables designed?
- Monolithic or Hybrid structure
- Most wearables communicate via smartphone (powerful and central part of system)
- Output via small screens on some devices (smartwatch)
- More desirable directly in viewing area (augmented reality)
What is augmented reality?
- Augment = Make greater
- Overlay and extend the reality
- This is the point behind wearables
- Increase humans cognitive functionalities
What AR approaches exist?
Two approaches:
- Augmentation of the devices -> Ubiquitous Computing
- Augmentation through personal device(s) -> Wearables
What is the purpose of augmented reality?
- Overlay information (bridge real and virtual world)
- Enhance perception (night vision, biometric parameters)
What are the benefits of augmented reality?
- Usability (direct link to reality)
- I/O anywhere (without infrastructure)
Explain the two types of head-mounted display in terms of AR (video-based and see-through, above)
- they combine real and virtual images
Video based:
- Real world is indirect
- Simple linkage of real and virtual image
- delayed perception of real world , lower resolution
See-through, above
- Display overlays view
- complex linkage of real and virtual image
- immediate perception
- -> Safety-critical applications
Explain how information can be displayed in AR
- Head stabilized (information anchored to the head, UI elements)
- Body-stabilized (Information anchored to the body)
- World - Stabilised (Information anchored to the world, i.e. at the position of the object like further information on those objects)
How can you track the objects that should be overlaid in AR
- Active Tracking: infrared senders, requires much infrastructure
- Passive/ Vision-based Tracking: Using computer vision (markers), computationally intensive, little to no infrastructure)
- Inertial Tracking: Determine position using motion sensors (accelerometers and rotation sensors gyroscopes); inaccurate through drifts
How can you track the viewpoint of the user in AR
- Relative to the object that should be overlaid: using orientation markers
- Relative to the environment: Position of the user, Viewing direction
- > Position of object to be overlaid is static and known
- > Additional data needed to link position to viewed objects
What are tangible user interfaces?
- Direct control of electronic or virtual objects through physical handles for control
What are the characteristics of tangible user interfaces?
- Physical representation is computationally coupled to digital information
- Physical representations embody mechanisms for interactive control
- Physical representations are perceptually coupled to digital representations
- Physical state embodies key aspects of the digital state of a system
Why are embedded system important in the context of pervasive computing ?
- They create a seamless experience as envisioned in pervasive computing
- Richer functionality can arise from high interconnection
- To make all these heterogeneous devices interact there is need for interoperability
