An embedded system can be defined as an autonomous electronic and computer system ,which is dedicated to a specifictask,withlimitedspatial and energy resources . The term” EmbeddedSystem “refers to both thehardware and softwareused. Embedded systemsperform predefined tasks and havebindingspecificationsto complete, which can be of order:- Space counted, with a limited memory space of the order of a few MB ( megabytes ) maximum.
They also use computers and real-time systems.
– The lowest energy consumption possible, due to the use of
autonomous sources , batteries, solar panels.
– Temporary, whose task execution time is determined, Multidisciplinary skills in terms of electronics (control and power), automatic and industrial computing are therefore necessary to design such systems.
Inside an ADSL modem / router. An example of an embedded system. The numbered parts include: (4) the microprocessor, (6) the RAM, and (7) the flash memory .
Characteristics:
Rather than universal systems with multiple tasks, embedded systems are designed to perform specific tasks. Some must meet real-time constraints for reasons of reliability and profitability. Others with few performance constraints can simplify the system and reduce manufacturing costs. Embedded systems are not always independent modules. Most often they are integrated into the device they control.
The software created for embedded systems is called firmware. It is stored in read-only memory or flash memory rather than in a hard disk. It works most often with limited hardware resources: a small, or no keyboard, a small screen and little memory. User Interface: Some embedded systems may not have a user interface (they are specialized in a single task). But this interface can also be similar to that of a computer operating system (for example a PDA). = > The simplest systems only include buttons, LEDs.
=> The most complex systems can have a touch screen or a screen with buttons to minimize space. The meaning of the buttons changes according to the screen and the selection is done naturally by pointing the desired function.
=> Handheld computers usually have a joystick style button for navigation.
=> With the explosion of the web, the manufacturers of embedded systems have proposed a new option: an interface to the style of a web page on a network connection. This avoids the cost of a sophisticated system while maintaining a complete interface on another computer, when necessary. Reliability:
Embedded systems are mostly in machines that must run continuously for many years without errors and, in some cases, fix errors themselves when they arrive. This is why software is always developed and tested more carefully than those for PCs.
The issue of reliability may include:
=> The system can not be turned off for repairs or it is inaccessible repairs.
For example : submarine cables, navigation beacons, boreholes …
=> The system must remain running for safety reasons. Often, backups are done by an operator.
In this case, the “soft mode” is tolerated.
for example: reactor control systems, chemical plants, train signals …
=> A shutdown of the system can cause huge monetary losses if it goes out.
For example: bridge or elevator systems, background transfers, trading rooms, sales or automatic services …
Realization of an embedded system:
Among the necessary equipment to realize an embedded system we find:
=> The documentation on the used components. This is the first source of information for development! => The basic tools of the electronics engineer ( soldering iron , insoleuse …). => Time analysis tools: oscilloscope , logic analyzer … => Basic components ( resistors , capacitors …). => A microprocessor or a microcontroller. => A cross compiler (
computer program that transforms source code written in a programming language (the source language) into another computer language (the target language ) ) .
==>A microcontroller programmer or an in-situ programmer. ( a feature that allows electronic components (microcontrollers in particular) to be programmed or reprogrammed ).
=> Anin-circuit emulator or ICE ( hardware device for debugging the software of an embedded system ). This equipment allows hardware and software debugging, however it remains expensive. => Systems Engineering
: multidisciplinary approach to define, develop and deploy systems embedding digital technologies.
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