We have a number of design metrics you need to put into consideration when designing embedded systems.
The following are some of the key design metrics used in embedded systems:
Contents
Performance
The instruction execution time in the system measures the performance. Smaller execution time means higher performance. For example, for a digital camera, shooting a 4M pixel still image in 0.5s shows the camera performance.
Power Dissipation
For battery operated systems like digital cameras, mobile phones, the power consumed by the system is a key feature. The battery needs to be recharged less frequently if power dissipation is small.
Size
The size of the system is measured in terms of physical space needed, Ram in kB and internal flash memory requirements in MB or GB for running the software and for data storage and the number of million logic gates in the hardware.
Flexibility
Flexibility in design enables, without any significant engineering cost, the development of different versions of a product and advanced versions later on. For instance, software enhancement by adding extra functions demanded the by changing environment and software re-engineering.
Process Deadlines
There are a number of processes in the system, for instance, keypad input processing, graphic display refresh, audio signals processing and video signals processing. These processes have deadlines within which each of them may be needed to finish the computation and provide the results.
Engineering Cost
This is the initial cost of developing, debugging and testing the hardware and software. This is one time non-recurring cost.
Manufacturing Cost
This is the cost of manufacturing each unit.
User Interfaces (UI)
These include keypad graphical user interfaces (GUIs) and voice user interfaces (VUIs).
Prototype Development Time
This is the time taken in days or months for developing the prototype as well as internal testing for system functionalities. In involves the engineering time and making the prototype time.
Time to Market
This is the time taken in days or months after the prototype development for the product to be available to the users and consumers.
System & User Safety
Safety in terms of accidental fall from say the hand, table, or phone hacking ability and tracing ability and terms of user safety when using a product for instance, automobile brake or engine.
Maintenance
Maintenance implies the changeability and additions to the system. Example of software maintenance is additional service or functional software. Example for data maintenance is additional ring-tones, video-clips, wallpapers in mobile phone or extending card expiry date in case of smart card. Example of hardware maintenance is additional memory or changing memory stick in mobile computer and digital camera.
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