Description
1.0 INTRODUCTION
A system is an arrangement in which all its unit assemble work together according to a set of rules. It can also be defined as a way of working, organizing or doing one or many tasks according to a fixed plan. For example, a watch is a time displaying system. Its components follow a set of rules to show time. If one of its parts fails, the watch will stop working. So we can say, in a system, all its subcomponents depend on each other, and this bring answer to the definition of embedded system (Heiser, 2017).
As its name suggests, Embedded means something that is attached to another thing. An embedded system can be thought of as a computer hardware system having software embedded in it. An embedded system can be an independent system or it can be a part of a large system. An embedded system is a micro-controller or microprocessor based system which is designed to perform a specific task (Heath, 2013).
An embedded system is a combination of computer hardware and software designed for a specific function. Embedded systems may also function within a larger system. The systems can be programmable or have a fixed functionality. Industrial machines, consumer electronics, agricultural and processing industry devices, automobiles, medical equipment, cameras, digital watches, household appliances, airplanes, vending machines and toys, as well as mobile devices, are possible locations for an embedded system(Heath, 2013).
While embedded systems are computing systems, they can range from having no user interface (UI) — for example, on devices designed to perform a single task — to complex graphical user interfaces (GUIs), such as in mobile devices. User interfaces can include buttons, LEDs (light-emitting diodes) and touchscreen sensing. Some systems use remote user interfaces as well (Kraft et al., 2015).
Embedded systems are used in a wide range of technologies across an array of industries. Some examples include:
Alarm Circuit:a fire alarm is an embedded system; it will sense only smoke.
- Modern cars commonly consist of many computers (sometimes as many as 100), or embedded systems, designed to perform different tasks within the vehicle. Some of these systems perform basic utility functions and others provide entertainment or user-facing functions. Some embedded systems in consumer vehicles include cruise control, backup sensors, suspension control, navigation systems and airbag systems(Heath, 2013).
- Mobile phones.These consist of many embedded systems, including GUI software and hardware, operating systems (OSes), cameras, microphones, and USB (Universal Serial Bus) I/O (input/output) modules.
- Industrial machines.They can contain embedded systems, like sensors, and can be embedded systems themselves. Industrial machines often have embedded automation systems that perform specific monitoring and control functions.
- Medical equipment.These may contain embedded systems like sensors and control mechanisms. Medical equipment, such as industrial machines, also must be very user-friendly so that human health isn’t jeopardized by preventable machine mistakes. This means they’ll often include a more complex OS and GUI designed for an appropriate UI.
1.2 COMPONENTS OF EMBEDDED SYSTEM
An embedded system has three components (Michael et al., 2016) −
- It has hardware.
- It has application software.
- It has Real Time Operating system (RTOS) that supervises the application software and provide mechanism to let the processor run a process as per scheduling by following a plan to control the latencies. RTOS defines the way the system works. It sets the rules during the execution of application program. A small scale embedded system may not have RTOS.
So we can define an embedded system as a Micro-controller based, software driven, reliable, real-time control system.
1.3 CHARACTERISTICS OF AN EMBEDDED SYSTEM
- Single-functioned− An embedded system usually performs a specialized operation and does the same repeatedly. For example: A pager always functions as a pager.
- Tightly constrained− All computing systems have constraints on design metrics, but those on an embedded system can be especially tight. Design metrics is a measure of an implementation’s features such as its cost, size, power, and performance. It must be of a size to fit on a single chip, must perform fast enough to process data in real time and consume minimum power to extend battery life.
- Reactive and Real time− Many embedded systems must continually react to changes in the system’s environment and must compute certain results in real time without any delay. Consider an example of a car cruise controller; it continually monitors and reacts to speed and brake sensors. It must compute acceleration or de-accelerations repeatedly within a limited time; a delayed computation can result in failure to control of the car.
- Microprocessors based− It must be microprocessor or micro-controller based.
- Memory− It must have a memory, as its software usually embeds in ROM. It does not need any secondary memories in the computer.
- Connected− It must have connected peripherals to connect input and output devices.
- HW-SW systems− Software is used for more features and flexibility. Hardware is used for performance and security.
1.4 ADVANTAGES AND DISADVANTAGES OF EMBEDDED SYSTEM
ADVANTAGES
- Easily Customization
- Low power consumption
- Low cost
- Enhanced performance
Disadvantages
- High development effort
- Larger time to market
1.5 BASIC STRUCTURE OF AN EMBEDDED SYSTEM
The following illustration shows the basic structure of an embedded system (Michael et al., 2016)−
- Sensor− It measures the physical quantity and converts it to an electrical signal which can be read by an observer or by any electronic instrument like an A2D converter. A sensor stores the measured quantity to the memory.
- A-D Converter− An analog-to-digital converter converts the analog signal sent by the sensor into a digital signal.
- Processor & ASICs− Processors process the data to measure the output and store it to the memory.
- D-A Converter− A digital-to-analog converter converts the digital data fed by the processor to analog data
- Actuator− An actuator compares the output given by the D-A Converter to the actual (expected) output stored in it and stores the approved output.
1.6 working principle of embedded system
Embedded systems always function as part of a complete device — that’s what’s meant by the term embedded. They are low-cost, low-power-consuming, small computers that are embedded in other mechanical or electrical systems. Generally, they comprise a processor, power supply, and memory and communication ports. Embedded systems use the communication ports to transmit data between the processor and peripheral devices — often, other embedded systems — using a communication protocol. The processor interprets this data with the help of minimal software stored on the memory. The software is usually highly specific to the function that the embedded system serves(Michael et al., 2016).
1.7 Characteristics of embedded systems
The main characteristic of embedded systems is that they are task-specific.
Additionally, embedded systems can include the following characteristics:
- typically, consist of hardware, software and firmware;
- can be embedded in a larger system to perform a specific function, as they are built for specialized tasks within the system, not various tasks;
- can be either microprocessor-based or micro-controller-based — both are integrated circuits that give the system compute power;
- are often used for sensing and real-time computing in internet of things (IoT) devices, which are devices that are internet-connected and do not require a user to operate;
- can vary in complexity and in function, which affects the type of software, firmware and hardware they use; and
- are often required to perform their function under a time constraint to keep the larger system functioning properly.
1.8 Structure of embedded systems
Embedded systems vary in complexity but, generally, consist of three main elements:
- The hardware of embedded systems is based around microprocessors and micro-controllers. Microprocessors are very similar to micro-controllers and, typically, refer to a CPU (central processing unit) that is integrated with other basic computing components such as memory chips and digital signal processors (DSPs). Micro-controllers have those components built into one chip (Barr, 2019).
- Software and firmware.Software for embedded systems can vary in complexity. However, industrial-grade micro-controllers and embedded IoT systems usually run very simple software that requires little memory.
- Real-time operating system.These are not always included in embedded systems, especially smaller-scale systems. RTOSes define how the system works by supervising the software and setting rules during program execution.
In terms of hardware, a basic embedded system would consist of the following elements:
- Sensors convert physical sense data into an electrical signal.
- Analog-to-digital (A-D) converters change an analog electrical signal into a digital one.
- Processors process digital signals and store them in memory.
- Digital-to-analog (D-A) converters change the digital data from the processor into analog data.
- Actuators compare actual output to memory-stored output and choose the correct one.
The sensor reads external inputs, the converters make that input readable to the processor, and the processor turns that information into useful output for the embedded system.
A diagram of the basic structure and flow of information in embedded systems.
1.9 Types of embedded systems
There are a few basic embedded system types, which differ in their functional requirements. They are:
- Mobile embedded systems are small-sized systems that are designed to be portable. Digital cameras are an example of this.
- Networked embedded systems are connected to a network to provide output to other systems. Examples include home security systems and point of sale (POS) systems.
- Standalone embedded systems are not reliant on a host system. Like any embedded system, they perform a specialized task. However, they do not necessarily belong to a host system, unlike other embedded systems. A calculator or MP3 player is an example of this.
- Real-time embedded systems give the required output in a defined time interval. They are often used in medical, industrial and military sectors because they are responsible for time-critical tasks. A traffic control system is an example of this.
Embedded systems can also be categorized by their performance requirements:
- Small-scale embedded systems often use no more than an 8-bit micro-controller.
- Medium-scale embedded systems use a larger micro-controller (16-32 bit) and often link micro-controllers together.
- Sophisticated-scale embedded systems often use several algorithms that result in software and hardware complexities and may require more complex software, a configurable processor and/or a programmable logic array.
There are several common embedded system software architectures, which become necessary as embedded systems grow and become more complex in scale. These include:
- Simple control loops call subroutines, which manage a specific part of the hardware or embedded programming.
- Interrupt controlled systems have two loops: a main one and a secondary one. Interruptions in the loops trigger tasks.
- Cooperative multitasking is essentially a simple control loop located in an application programming interface (API).
- Preemptive multitasking or multith reading is often used with an RTOS and features synchronization and task switching strategies.
Very large-scale integration, or VLSI, is a term that describes the complexity of an integrated circuit (IC). VLSI is the process of embedding hundreds of thousands of transistors into a chip, whereas LSI (large-scale integration) microchips contain thousands of transistors, MSI (medium-scale integration) contains hundreds of transistors, and SSI (small-scale integration) contains tens of transistors. ULSI, or ultra-large-scale integration, refers to placing millions of transistors on a chip(Moratelli et al., 2016).
VLSI circuits are common features of embedded systems. Many ICs in embedded systems are VLSIs, and the use of the VLSI acronym has largely fallen out of favor.
1.9 HISTORY OF EMBEDDED SYSTEMS
Embedded systems date back to the 1960s. Charles Stark Draper developed an integrated circuit in 1961 to reduce the size and weight of the Apollo Guidance Computer, the digital system installed on the Apollo Command Module and Lunar Module. The first computer to use ICs, it helped astronauts collect real-time flight data(Moratelli et al., 2016).
In 1965, Autonetics, now a part of Boeing, developed the D-17B, the computer used in the Minuteman I missile guidance system. It is widely recognized as the first mass-produced embedded system. When the Minuteman II went into production in 1966, the D-17B was replaced with the NS-17 missile guidance system, known for its high-volume use of integrated circuits. In 1968, the first embedded system for a vehicle was released; the Volkswagen 1600 used a microprocessor to control its electronic fuel injection system (Tancreti et al., 2015).
Also, in 1971, Intel released what is widely recognized as the first commercially available processor, the 4004. The 4-bit microprocessor was designed for use in calculators and small electronics, though it required eternal memory and support chips. The 8-bit Intel 8008, released in 1972, had 16 KB of memory; the Intel 8080 followed in 1974 with 64 KB of memory. The 8080’s successor, the x86 series, was released in 1978 and is still largely in use today(Tancreti et al., 2015).
In 1987, the first embedded operating system, the real-time VxWorks, was released by Wind River, followed by Microsoft’s Windows Embedded CE in 1996. By the late 1990s, the first embedded Linux products began to appear. Today, Linux is used in almost all embedded devices(Tancreti et al., 2015).
1.10 Embedded system trends
While some embedded systems can be relatively simple, they are becoming more complex, and more and more of them are now able to either supplant human decision-making or offer capabilities beyond what a human could provide. For instance, some aviation systems, including those used in drones, are able to integrate sensor data and act upon that information faster than a human could, permitting new kinds of operating features (Moratelli et al., 2016).
The embedded system is expected to continue growing rapidly, driven in large part by the internet of things. Expanding IoT applications, such as wearables, drones, smart homes, smart buildings, video surveillance, 3D printers and smart transportation, are expected to fuel embedded system growth.
1.11 Conclusion
Embedded Systems carried out in this work provides basic and advanced concepts of Embedded System.
Embedded System is a system composed of hardware, application software and real time operating system. It can be small independent system or large combinational system.
This study includes all the necessary and basic information about embedded system.
