History :-

*One of the first recognizably modern embedded systems was the Apollo Guidance Computer, developed by Charles Stark Draper at the MIT Instrumentation Laboratory.

*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.

What is an EMBEDDED OS?What is an EMBEDDED OS?

An embedded system is generally a system within a larger system. All embedded systems contain a

processor and software . Modern cars and

trucks contain many embedded systems. One embedded system controls anti-lock brakes,

another - monitors and controls vehicle's emission and a third displays information on the dashboard. Even the general-purpose , personal computer itself is made up of numerous embedded systems. Keyboard,

mouse, video card, modem, hard drive, floppy drive and sound card each of them is an EMBEDDED SYSTEM.

EMBEDDED OS EXAMPLES : WATCH - It is a time display SYSTEM .

PARTS : Hardware, Needles, Battery,

Dial, Chassis and Strap.

RULES :1. All needles move clockwise only.

2. A thin needle rotates every second.

3. A long needle rotates every minute.

4. A short needle rotates every hour.

5. All needles return to the original

position after 12 hours.

WASHING MACHINE

- It is an automatic Washing SYSTEM .

PARTS : Status display panel, Switches & Dials, Motor, Power supply & Control Unit, Inner water level sensor

& solenoid valve.

RULES :1. Wash by spinning.

2. Rinse.

3. Drying.

4. Wash over by blinking.

5. Each step displays the process

stage.

COMPONENTS OF EMBEDDED OS It has Hardware Processors, Timers, Interrupt Controller, I/O Devices,

Memories, Ports, etc.

It has main Application Software Which may perform concurrently the series of tasks or

multiple tasks.

It has Real Time Operating System (RTOS) RTOS defines the way the system work. Which supervise

the application software. It sets the rules during the execution of the application program. A small scale embedded system may not need an RTOS.

Real time operating systemReal time operating system 1)Real-time Operating System allows real-time

applications to be designed and expanded

easily. 2)Functions can be added without major changes to

the software. 3)The use of an RTOS further simplifies the design

process by splitting the application code Real-time computing is where system correctness not only depends on the correctness of logical result but also on the result delivery time.

4) the operating system should have features to support this critical requirement to render it to be termed a Real-time operating into separate tasks

For eg; In a computer itself , there are many Embedded Operating Systems .

PC

Keyboard

Mouse

Modem

Hard Drive

Floppy Drive

Video Card

EMBEDDED SYSTEM CONSTRAINTSAn embedded system is software designed to

keep in view three constraints :

Available system memory.

Available processor speed.

The need to limit the power dissipation. When running the system continuously in cycles of wait for

events , run, stop and wakeup.

Classification of Embedded Systems Small Scale Embedded System

Medium Scale Embedded System

Sophisticated Embedded System

Small Scale Embedded OS Single 8 bit or 16 bit Microcontroller. Little Hardware and Software complexity. They may even be battery operated. Usually “C” is used for developing these systems. The need to limit power dissipation when system is

running continuously.

Programming tools : Editor, Assembler and Cross Assembler.

Medium Scale Embedded OS Single or few 16 or 32 bit microcontrollers or Digital Signal

Processors (DSP) or Reduced Instructions Set Computers (RICS).

Both hardware and software complexity.

Programming tools : RTOS, Source code Engineering tools, Simulator, Debugger and Integrated Development Environment (IDE).

Sophisticated Embedded OS Enormous hardware and software complexity.

Which may need scalable processor or configurable processor and programming logic arrays.

Constrained by the processing speed available in their hardware units.

Programming tools : For these systems may not be readily available at a reasonable cost or may not be even be available at all. A compiler or retargetable compiler might have to be developed for this.

Characteristics of Embedded OS : Embedded systems are designed to do a

specific task, unlike general-purpose computers. Some embedded systems have real-time "performance constraints" that must be met, for reasons such as safety and usability; without constraints the systems are simplified at law price.

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. Similarly, an embedded system in an car provides a specific function as a subsystem of the car itself.

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.

Advantages of Embedded OS : 1. Design and Efficiency

The central processing core in embedded systems is generally less complicated, making it easier to maintain. The limited function required of embedded systems allows them to be designed to most efficiently perform their functions.

Cost•The streamlined make-up of most embedded systems allows their parts to be smaller less expensive to produce.

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2. Cost

The streamlined make-up of most Embedded systems allows their parts to be smaller less expensive to produce.

3. Maintenance

Embedded systems are easier to maintain because the supplied power is embedded in the system and does not require remote maintenance.

4. Accessibility

Embedded systems are difficult to service because they are inside another machine, so a greater effort is made to carefully develop them. However, if something does go wrong with certain embedded systems they can be too inaccessible to repair. This concern is sometimes addressed in the design stage, such as by programming an embedded system so that it will not affect related systems negatively when malfunctioning.

Basic Difference between : General Computer and Embedded OS

An embedded system has historically been defined as a SINGLE function product where the intelligence is embedded in the system. It could be anything from a dishwasher to a hearing aid, if that product includes a microprocessor and software.

A PC is designed to be a general purpose computing environment.Many of today’s embedded systems are looking more like PCs with user interfaces, touch-screen, display, keypads and more. Still, these are not general function systems but are designed to perform very specific function.