Embedded system
embedded a specialized —a of a , memory, and input/output —that a dedicated a larger mechanical or . embedded as part of a device often including electrical or hardware and mechanical . Because embedded physical of the that embedded , often real-time computing Embedded control many common use. In 2009[update], that of all used embedded .
Modern embedded are often on (i.e. with integrated memory and ), but ordinary (using chips for memory and interface ) are also common, especially more . , the (s) used be from general purpose to those specialized a of , or even custom for the at hand. A common standard of dedicated the digital (DSP).
Since the embedded dedicated to , design engineers to reduce the size and cost of the and increase reliability and performance. Some embedded are , from .
Embedded range size from personal as digital and MP3 players to bigger like home appliances, industrial , robots, vehicles, traffic light , and medical imaging . Often they of other like aircraft and . Large like , and electrical on embedded together. through software , embedded as their .
Embedded range from those low , with a chip, to very high with , and , which equipment or large connected via
Background
The origins of the and the be back to the MOS integrated , which integrated chip from (metal– ) and developed the early 1960s. By 1964, MOS chips reached higher transistor and lower manufacturing than bipolar chips. MOS chips at a rate law, leading to (LSI) with of on a MOS chip by the late 1960s. The of MOS LSI chips to computing the basis for the first , as engineers that a be on several MOS LSI chips.
The first , the 1969 and the Garrett MP944 1970, developed with MOS LSI chips. The first the Intel 4004, 1971. developed by Federico , using MOS , with Intel engineers Hoff and , and engineer Shima.
Development
One of the first modern embedded the Apollo , developed ca. 1965 by Charles Stark Draper at the MIT Laboratory. At the inception, the Apollo considered the item the Apollo as the then developed integrated to reduce the size and weight.
early embedded the for the , 1961. When the into 1966, the with a new that the first use of integrated .
Since early the 1960s, embedded have come down price and a rise processing power and . early , the Intel 4004 ( 1971), for and other small but still required memory and support chips. By the early 1980s, memory, input and output integrated into the chip as the a . find where a be too . As the cost of and , the of embedded . be to the as a large number of separate . With , feasible to replace, even consumer , analog as and with up/down or read out by a . this embedded usually more than a , of the the . Very additional be needed and of the design effort the software. Software and be with the design and of a new not using embedded .
Embedded are found consumer, industrial, , home appliances, medical, telecommunication, , and
embedded from for the network to cell at the end user. networking dedicated and network to data.
Consumer include MP3 , mobile , video game , digital , and . appliances, as microwave, washing and , include embedded to provide , and . , , and air conditioning use to more and control that change by time of day and season. Home automation and wireless networking that be used to control , ,audio/visual, etc.all of which use embedded for and .
Medical equipment embedded for monitoring, and various medical imaging (PET), (CT), and imaging () for internal . Embedded medical equipment are often powered by industrial computers.
Embedded are used for and defense industries. connected to or wireless via 3G or other for monitoring and control , be from hacking and be more . For fire safety, the be to have a greater ability to handle higher and continue to . with , the embedded be and be able to deal with cut electrical and
Miniature wireless are wireless sensors. Wireless sensor networking use of made possible by integrated (IC) design to full wireless to sensors, people and to measure a of the physical world and on this information through monitoring and control . are completely and will run off a source for before the need to be changed or .
Embedded are to perform a task, contrast with computers for . Some have real-time performance that be met, for as safety and ; have low or no performance , the hardware to be to reduce .
Embedded are not always . Many embedded are a small part a larger device that a more general purpose. For example, the Gibson Robot Guitar embedded for tuning the strings, but the overall purpose of the Robot Guitar to play music. ,embedded a as a of the car .
The program written for embedded are to as firmware, and are stored memory or flash memory chips. They run with limited hardware : little memory, small or keyboard or screen.
User
Embedded range from no user interface at all, dedicated to one task, to user that modern desktop operating . embedded use , (LED), or (LCD) with a menu . More that use a screen with touch or soft provide space used: the meaning of the change with the screen, and the natural behavior of at what.
Some provide user interface with the help of a serial (e.g. RS-232) or network (e.g. Ethernet) . This the of the embedded , the cost of a display, the board support package (and designers to build a rich user interface on the PC. A good example of this the of embedded HTTP server running on embedded device ( as IP or a network router). The user interface a web browser on a PC connected to the device.
embedded
of embedded computers when with , are low power , small size, operating , and low cost. This comes at the of limited processing .
have developed for embedded use. are also used embedded , but generally, require more support than .
PC/104 and PC/104+ are of for for small, embedded and . are and often small to a standard PC, still quite large to (8/16-bit) embedded . They use DOS, Linux, or embedded real-time operating ) QNX or
, where small size or power are not primary , the 0used be with those used personal computers. as the VIA range help to bridge the gap by but integrated, or have other making to embedded engineers. The advantage of this that be used with the software development tools used for general software development. built this way are still as embedded since they are integrated into larger and a . of that this are teller (ATM) and arcade , which code to the .
However, embedded are not and do not use the or PCI . When a , be little benefit to having a bus connecting , and the for both hardware and software tools be very different.
One common design style a small , perhaps the size of a card, holding high chips as and , flash memory for storage, and for runtime memory. The vendor will usually provide boot software and make sure a of operating , usually including Linux and some real-time . be high volume, by familiar with their specialized testing , and with much lower volume custom with . of this include Arduino and Pi.
A on a chip a system - of , , , even different of memory and various like for or wireless on a chip. Often processing (GPU) and are included chips. be implemented as integrated () or using a gate array () which be .
are common for embedded like mobile and . or be used for embedded with kind of processing performance, and reliability, like .
Embedded talk with the outside world via , as:
- Serial (SCI): RS-232, RS-422, RS-485, etc.
- Serial Interface: , SPI, SSC and ( Serial Interface)
- Universal Serial Bus (USB)
- Media cards (SD cards, , etc.)
- Network interface controller: Ethernet, WiFi, etc.
- : bus, , etc.
- : loops, interval
- General Purpose Input/Output )
- and
- programming, background debug mode interface port, , and ports.
Tools
As with other software, embedded designers use , , and to develop embedded software. However, they also use more tools:
- or (see next ).
- Utilities to add a or to a program, so the embedded check the program valid.
- For using digital processing, use a notebook to the mathematics.
- modeling and simulation tools help designers to simulation of a with hardware as , memories,and software behavior flow as a state diagram or flow diagram using library . Simulation to select the right by performing power vs. performance , reliability and . that help a designer to make architecture include , device , device , power of the full as well as power .
- A development tool and data flow and state chart of like digital , motor , and .
- Custom and be used to specialized hardware.
- embedded have own language or design tool, or add to language as or Basic.
- Another to add a or embedded operating
- Modeling and code tools often on state
Software tools come from several :
- Software that the embedded market
- from the software development tools
- Sometimes, development tools for a personal be used the embedded a close to a common PC
Embedded software often a of development tools, including programming as C++, or , and like Qt for . tools enable to create efficient, , and to the of embedded . The choice of tools by as real-time performance, with hardware, or .
As the of embedded , tools and operating are into machinery where sense. For example, , personal digital and other consumer computers often need software that or by a person other than the of the . , open programming as Linux, , , or Embedded Java required so that the software provider to a large market.
Embedded be at different , on the available. include: does slow down the main , how close the or to the or , how are the that be set for (e.g., the memory when a program counter value reached), and what be the ( as, only memory, or memory and , etc.).
From to and are into the following :
- Interactive resident debugging, using the simple shell provided by the embedded operating system (e.g. Forth and Basic)
- have the benefit that they do not need any hardware but have to control what they record order to time and storage space.
- using logging or serial port output to trace using a monitor flash or using a debug server like the Remedy that even for .
- (), a hardware device that to the via a or Nexus interface. This the of the to be , but to the .
- emulator (ICE) the with a , full control over all of the .
- A emulator a simulation of all of the hardware, all of to be and modified, and on a normal PC. The are and slow , some cases up to 100 times than the final .
- For , the to verify and debug the design on board. Tools as are used to insert the implementation that make available for . This used to debug hardware, firmware and software implementation with similar to a analyzer.
to , the programmer load and run software through the tools, view the code running the , and start or stop . The view of the code be as programming language, code or of both.
Real-time operating often support of operating . A view by a host PC tool, on a recording of the behavior. The trace recording be software, by the , or by hardware. to understand timing and performance of the software and a good understanding of the . Trace recording embedded be using hardware or software . trace recording does not require specialized hardware and be used to record , but have impact on and RAM usage. One example of a used the use of empty which are by the operating at the code, and be implemented to serve as hooks.
Reliability
Embedded often ine that are expected to run for without , and some cases by , the software usually developed and tested more than that for personal computers, and mechanical moving as disk drives, or are .
reliability include:
- The be shut down for repair, or too to repair. include space , and automobiles.
- The be running for safety . the event of failure be.Often are selected by operator. include aircraft , control , factory , train .
- The will lose large of money when shut down: , factory bridge and elevator ,transfer and market making, and .
A of are used, sometimes , to from —both software as memory,and also soft the hardware:
- timer that and the the software the
- (with a computing base ) architecture
- programming help engineers produce more reliable embedded code. and coding as C/C++ aim to assist produce reliable, firmware a number of different : by or coding which lead to (memory , invalid pointer ), use of checks and (range/ checks, and buffer index checks, default cases checks), loop , of , well and well code, and language which lead to or ( of macro). often be used with code or model for , and also assist of code timing .
High vs. low volume
For as mobile , cost usually the primary design . Engineers select hardware that just good enough to implement the necessary .
For or embedded , computers be by the programs or by the operating with.
Embedded software
1978 Electrical ICS 3-1978, a standard for , including almost any , as computers, , and .
are several different of software architecture common use.
control loop
this design, the software simply a loop which the input . The loop , each of which a part of the hardware or software. a control loop or
Some embedded are by . This that by the are by different of be , for example, by a timer at a interval, or by a serial port controller data.
This architecture used event need low , and the event are short and . run a task a main loop also, but this task not very sensitive to Sometimes the handler will add longer to a structure. Later, after the handler finished, are executed by the main loop. This the close to a multitasking kernel with .
multitasking very similar to the control loop , except that the loop hidden API. The programmer a series of , and each task gets own to run . When a task idle, idle which control to another task.
The and are similar to that of the control loop, except that adding new software easier, by simply writing a new task, or adding to the .
As any code damage the data of another task (except using a memory management unit) programs be and tested, and to data be by some as message , or a
Because of , common for to use , the to on device than operating . The choice to include own , however, as the be made to starting the development . This timing to choose the embedded operating for their device on current and so future options to a large .
The level of embedded growing as are required to manage and as serial, USB, TCP/IP, Bluetooth, Wireless LAN, radio, channels, data and voice,
by normal . The hardware and all the software the are available to and by .
A kernel a large kernel with to suit embedded . This similar to a desktop operating like Linux or Microsoft Windows, and very for development. On the , more hardware , often more , and, because of the of , be less and reliable.
Common of embedded are embedded Linux, and Windows C