Collaboration of hardware and software

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ABSTRACT

Embedded is collaboration of hardware and software with the help of software called simulators and we used a kit to write program in microprocessor. Embedded systems are based on the concept of the microcontroller, a single integrated circuit that contains all the technology required to run an application. Embedded systems are controlled by a main processing core that is typically either a microcontroller or a digital signal processor (DSP). Main concept of embedded system and key element is real time operating system (RTOS).

INTRODUCTION

Embedded systems control many of the common devices in use today.

Embedded systems are controlled by a main processing core that is typically either a microcontroller or a digital signal processor (DSP).

Since the embedded system is dedicated to specific tasks, design engineers can optimize it reducing the size and cost of the product and increasing the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale.Physically, embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants.

Embedded systems refer to devices, instruments or large engineering structures/systems that are built to handle one or a few pre-established tasks. The computer controlling the whole thing is built into or 'embedded' within the device. . Embedded systems that are programmable are provided with programming interfaces, and embedded systems programming is a specialized occupation.

FEATURES OF EMBEDDED SYSTEMS

Embedded systems are based on the concept of the microcontroller, a single integrated circuit that contains all the technology required to run an application. Microcontrollers make integrated systems possible by combining several features together into what is effectively a complete computer on a chip, including:

  • Central Processing Unit
  • Input/Output interfaces (such as serial ports)
  • Peripherals (such as timers)
  • ROM, EEPROM or Flash memory for program storage
  • RAM for data storage
  • Clock generator

HISTORY

One of the first recognizably modern embedded systems was the Apollo Guidance Computer, developed by Charles Stark Draper at the MIT Instrumentation Laboratory. At the project's inception, the Apollo guidance computer was considered the riskiest item in the Apollo project as it employed the then newly developed monolithic integrated circuits to reduce the size and weight. An early mass-produced embedded system was the Autonetics D-17 guidance computer for the Minuteman missile, released in 1961. It was built from transistor logic and had a hard disk for main memory. When the Minuteman II went into production in 1966, the D-17 was replaced with a new computer that was the first high-volume use of integrated circuits. This program alone reduced prices on quad nand gate ICs from $1000/each to $3/each, permitting their use in commercial products.

Since these early applications in the 1960s, embedded systems have come down in price and there has been a dramatic rise in processing power and functionality. The first microprocessor for example, the Intel 4004, was designed for calculators and other small systems but still required many external memory and support chips. In 1978 National Engineering Manufacturers Association released a "standard" for programmable microcontrollers, including almost any computer-based controllers, such as single board computers, numerical, and event-based controllers.

As the cost of microprocessors and microcontrollers fell it became feasible to replace expensive knob-based analog components such as potentiometers and variable capacitors with up/down buttons or knobs read out by a microprocessor even in some consumer products.

By the mid-1980s, most of the common previously external system components had been integrated into the same chip as the processor and this modern form of the microcontroller allowed an even more widespread use, which by the end of the decade were the norm rather than the exception for almost all electronics devices.

The integration of microcontrollers has further increased the applications for which embedded systems are used into areas where traditionally a computer would not have been considered. Although in this context an embedded system is usually more complex than a traditional solution, most of the complexity is contained within the microcontroller itself. Very few additional components may be needed and most of the design effort is in the software. The intangible nature of software makes it much easier to prototype and test new revisions compared with the design and construction of a new circuit not using an embedded processor.

CHARACTERISTICS

An embedded system targeted at network applications.

a) Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real-time performance constraints that must be met, for reasons such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs.

b) Embedded systems are not always standalone devices. Many embedded systems consist of small, computerized parts within a larger device that serves a more general purpose. For example, the Gibson Robot Guitar features an embedded system for tuning the strings, but the overall purpose of the Robot Guitar is, of course, to play music.[5] Similarly, an embedded system in an automobile provides a specific function as a subsystem of the car itself.

c) The program instructions written for embedded systems are referred to as firmware, and are stored in read-only memory or Flash memory chips. They run with limited computer hardware resources: little memory, small or non-existent keyboard and/or screen.

d) REAL-TIME OPERATING SYSTEM: Most of the embedded systems works on the real-time operating system (RTOS) and important for every embedded system. A Real-Time Operating System (RTOS) is a multitasking operating system intended for real-time applications. Such applications include embedded systems (programmable thermostats, household appliance controllers), industrial robots, spacecraft, industrial control (see SCADA), and scientific research equipment. A RTOS facilitates the creation of a real-time system, but does not guarantee the final result will be real-time; this requires correct development of the software. An RTOS does not necessarily have high throughput; rather, an RTOS provides facilities which, if used properly, guarantee deadlines can be met generally or deterministically (known as soft or hard real-time, respectively).

e) PROCESSORS EMBEDDED SYSTEMS

Embedded processors can be broken into two broad categories: ordinary microprocessors (µP) and microcontrollers (µC), which have many more peripherals on chip, reducing cost and size. Contrasting to the personal computer and server markets, a fairly large number of basic CPU architectures are used; there are Von Neumann as well as various degrees of Harvard architectures, RISC as well as non-RISC and VLIW; word lengths vary from 4-bit to 64-bits and beyond (mainly in DSP processors) although the most typical remain 8/16-bit. Most architecture comes in a large number of different variants and shapes, many of which are also manufactured by several different companies.

Common architectures are:

65816, 65C02, 68HC08, 68HC11, 68k, 8051, ARM, AVR, AVR32, Blackfin, C167, Coldfire, COP8, Cortus APS3, eZ8, eZ80, FR-V, H8, HT48, M16C, M32C, MIPS, MSP430, PIC, PowerPC, R8C, SHARC, ST6, SuperH, TLCS-47, TLCS-870, TLCS-900, Tricore, V850, x86, XE8000 etc.

PERIPHERALS

Embedded Systems talk with the outside world via peripherals, such as:

  • Serial Communication Interfaces (SCI): RS-232, RS-422, RS-485 etc
  • Synchronous Serial Communication Interface: I2C, SPI, SSC and ESSI (Enhanced Synchronous Serial Interface)
  • Universal Serial Bus (USB)
  • Multi Media Cards (SD Cards, Compact Flash etc)
  • Networks: Ethernet, Controller Area Network, LonWorks, etc
  • Timers: PLL(s), Capture/Compare and Time Processing Units
  • Discrete IO: aka General Purpose Input/Output (GPIO)
  • Analog to Digital/Digital to Analog (ADC/DAC)
  • Debugging: JTAG, ISP, ICSP, BDM Port

TOOLS

Embedded system designers use compilers, assemblers, and debuggers to develop embedded system software. Some more specific tools are:

  • In circuit debuggers or emulators.
  • Utilities to add a checksum or CRC to a program, so the embedded system can check if the program is valid.
  • For systems using digital signal processing, developers may use a math workbench such as Scilab / Scicos, MATLAB / Simulink, EICASLAB, MathCad, or Mathematica to simulate the mathematics. They might also use libraries for both the host and target which eliminates developing DSP routines as done in DSPnano RTOS and Unison Operating System.
  • Custom compilers and linkers may be used to improve optimisation for the particular hardware.
  • An embedded system may have its own special language or design tool, or add enhancements to an existing language such as Forth or Basic.
  • Another alternative is to add a real-time operating system or embedded operating system, which may have DSP capabilities like DSPnano RTOS.
  • Software companies that specialize in the embedded market
  • Ported from the GNU software development tools
  • Sometimes, development tools for a personal computer can be used if the embedded processor is a close relative to a common PC processor

As the complexity of embedded systems grows, higher level tools and operating systems are migrating into machinery where it makes sense. For example, cellphones, personal digital assistants and other consumer computers often need significant software that is purchased or provided by a person other than the manufacturer of the electronics.

DEBUGGING

Embedded debugging may be performed at different levels, depending on the facilities available. It can be classified into the following areas:

  • Interactive resident debugging, using the simple shell provided by the embedded operating system (e.g. Forth and Basic)
  • External debugging using logging or serial port output to trace operation using either a monitor in flash or using a debug server like the Remedy Debugger which even works for heterogeneous multico-re systems.
  • An in-circuit debugger (ICD), a hardware device that connects to the microprocessor via a JTAG or NEXUS interface. This allows the operation of the microprocessor to be controlled externally, but is typically restricted to specific debugging capabilities in the processor.
  • An in-circuit emulator replaces the microprocessor with a simulated equivalent, providing full control over all aspects of the microprocessor.
  • A complete emulator provides a simulation of all aspects of the hardware, allowing all of it to be controlled and modified and allowing debugging on a normal PC.

Unless restricted to external debugging, the programmer can typically load and run software through the tools, view the code running in the processor, and start or stop its operation. The view of the code may be as assembly code or source-code.

Because an embedded system is often composed of a wide variety of elements, the debugging strategy may vary. For instance, debugging a software- (and microprocessor-) centric embedded system is different from debugging an embedded system where most of the processing is performed by peripherals (DSP, FPGA, co-processor). An increasing number of embedded systems today use more than one single processor core. A common problem with multi-core development is the proper synchronization of software execution. In such a case, the embedded system design may wish to check the data traffic on the busses between the processor cores, which requires very low-level debugging, at signal/bus level, with a logic analyzer, for instance.

RELIABILITY

Embedded systems often reside in machines that are expected to run continuously for years without errors and in some cases recover by them if an error occurs. Therefore the software is usually developed and tested more carefully than that for personal computers, and unreliable mechanical moving parts such as disk drives, switches or buttons are avoided. Specific reliability issues may include:

  1. The system cannot safely be shut down for repair, or it is too inaccessible to repair. Examples include space systems, undersea cables, navigational beacons, bore-hole systems, and automobiles.
  2. The system must be kept running for safety reasons. "Limp modes" are less tolerable. Often backups are selected by an operator. Examples include aircraft navigation, reactor control systems, safety-critical chemical factory controls, train signals, engines on single-engine aircraft.
  3. The system will lose large amounts of money when shut down: Telephone switches, factory controls, bridge and elevator controls, funds transfer and market making, automated sales and service.

A variety of techniques are used, sometimes in combination, to recover from errors-both software bugs such as memory leaks, and also soft errors in the hardware:

  • watchdog timer that resets the computer unless the software periodically notifies the watchdog
  • subsystems with redundant spares that can be switched over to
  • software "limp modes" that provide partial function
  • Designing with a Trusted Computing Base (TCB) architecture[6] ensures a highly secure & reliable system environment

CHARACTERISTICS

An embedded system targeted at network applications.

  1. Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real-time performance constraints that must be met, for reasons such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs.
  2. The program instructions written for embedded systems are referred to as firmware, and are stored in read-only memory or Flash memory chips. They run with limited computer hardware resources: little memory, small or non-existent keyboard and/or screen
  3. Embedded systems are not always standalone devices. Many embedded systems consist of small, computerized parts within a larger device that serves a more general purpose. For example, the Gibson Robot Guitar features an embedded system for tuning the strings, but the overall purpose of the Robot Guitar is, of course, to play music.[5] Similarly, an embedded system in an automobile provides a specific function as a subsystem of the car itself.

USER INTERFACE

Embedded systems range from no user interface at all - dedicated only to one task - to complex graphical user interfaces that resemble modern computer desktop operating systems. Simple embedded devices use buttons, LEDs, graphic or character LCDs (for example popular HD44780 LCD) with a simple menu system.

A more sophisticated devices use graphical screen with touch sensing or screen-edge buttons provide flexibility while minimizing space used: the meaning of the buttons can change with the screen, and selection involves the natural behavior of pointing at what's desired. Handheld systems often have a screen with a "joystick button" for a pointing device.

Originally, an embedded system had no user interface - information and programs were already incorporated into the system (e.g., the guidance system for an Intercontinental Ballistic Missile or ICBM) and there was no need for human interaction or intervention except to install the device and test it.

Many modern embedded systems however, have full-scale user interfaces although these are only inputs for data but are not supposed to provide additional functionality for the system, e.g. QWERTY keyboards for PDAs used to enter names, addresses, phone numbers and notes and even full sized documents. The moment PDAs achieve full desktop computer functionalities, however, they may no longer be considered embedded systems.

DOWNFALLS OF EMBEDDED SYSTEMS

When problems develop with a personal computer the manufacturers can develop and release a software patch to their customers, who can then rectify the problem themselves. Embedded systems are not designed for user interaction, so the majority of embedded systems are just that - embedded within the product, with no easy method of updating or repairing their software.

Since embedded systems are often used to control such functions as braking in an automobile or the guidance system on an intercontinental missile they cannot be released onto the market before they have been extensively tested and retested. Quite simply, there can be no margin of error. As a result the cost of embedded systems can often be deceptively high. While the manufacturing costs are reduced, the testing and quality control costs can be higher than expected.

USE OF EMBEDDED SYSTEM

Some of the uses in daily use are:

Telecommunications systems employ numerous embedded systems from telephone switches for the network to mobile phones at the end-user. Computer networking uses dedicated routers and network bridges to route data.

Consumer electronics include personal digital assistants (PDAs), mp3 players, mobile phones, videogame consoles, digital cameras, DVD players, GPS receivers, and printers. Many household appliances, such as microwave ovens, washing machines and dishwashers, are including embedded systems to provide flexibility, efficiency and features..

Transportation systems from flight to automobiles increasingly use embedded systems. New airplanes contain advanced avionics such as inertial guidance systems and GPS receivers that also have considerable safety requirements. Various electric motors - brushless DC motors, induction motors and DC motors - are using electric/electronic motor controllers. Automobiles, electric vehicles, and hybrid vehicles are increasingly using embedded systems to maximize efficiency and reduce pollution. Other automotive safety systems include anti-lock braking system (ABS), Electronic Stability Control (ESC/ESP), traction control (TCS) and automatic four-wheel drive.

Medical equipment is continuing to advance with more embedded systems for vital signs monitoring, electronic stethoscopes for amplifying sounds, and various medical imaging (PET, SPECT, CT, MRI) for non-invasive internal inspections.

In addition to commonly described embedded systems based on small computers, a new class of miniature wireless devices called motes is quickly gaining popularity as the field of wireless sensor networking rises. Wireless sensor networking, WSN, makes use of miniaturization made possible by advanced IC design to couple full wireless subsystems to sophisticated sensors, enabling people and companies to measure a myriad of things in the physical world and act on this information through IT monitoring and control systems. These motes are completely self contained, and will typically run off a battery source for many years before the batteries need to be changed or charged.

CONCLUSION

Embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants. Every electronic device is an embedded system (except computer).It has become an important part of our life

REFERENCES

  1. Wikipedia.com
  2. Google.com
  3. Embedded system designing
  4. Embeddedsystem.com

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