EMBEDDED SYSTEM

 Introduction: 

 ➢ It is an electro-mechanical system designed to perform a specific function and combination of hardware & software.

 ➢ Embedded Systems are becoming an expected part of any product in all fields including household appliances, telecommunication, medical products, etc. 

➢ Embedded system is a combination of 

 1. Hardware 2. Software 3. Mechanical components.

First Generation:-

 Built around an 8-bit microprocessor and 4-bit microcontroller.

 Simple in hardware circuit and software developed in assembly code.

Second Generation:-

  Built around 16-bit microprocessor & 8-bit microcontroller.

  The instruction set is more complex and powerful than the first generation.

Third Generation:-

 Built around a 32-bit microprocessor and 16-bit microcontroller. 

 New Concepts like DSP (Digital Signal Processors) are used. 

Fourth Generation:-

 Built around a 64-bit microprocessor and 32-bit microcontroller 

 Highly complex and more powerful 

 The concepts of Systems on Chips, Multicore Processor evolved to have high performance.

On Complexity and Performance:-

 ❖ Small Scale : 

➢ Application need is simple. 

➢ Performance requirements are not time critical. 

➢ Small-scale embedded system built around low cost and low performance. 

➢ Example: an electronic toy.

❖ Medium scale : 

➢ Hardware and software requirements are slightly difficult. 

➢ Built around medium performance and low-cost microprocessor or microcontroller. 

➢ Usually contain an embedded operating system for functioning. 

➢ Example: industrial machines.

 ❖ Large scale : 

➢ Hardware and software are highly difficult. 

➢ Assembled 32 or 64-bit RISC µP / µC. 

➢ It is a real-time operating system. 

➢ Example: Mission-critical applications 

 Why do we need an embedded system?

 a) General-purpose computers like PCs would be far more costly as compared to embedded system products.

 b) General-purpose solutions fail to meet functional or performance requirements like power consumption, size limitation, reliability,  etc.

Purpose of Embedded System:-

 Data collection/Storage/Representation 

1. Data collection is usually done for storage, analysis, manipulation, and transmission. 

2. Data can be analog or digital. 

3. Analog data to digital data conversion by analog to digital converter. 

4. Digital data- directly captured by a digital embedded system.

 Data Communication 

1. Used in communication systems from complex satellite communication to simple home networking system 

2. Data transmission can be wired or wireless 

3. Data can be transmitted by analog or digital means 

4. Wireless modules: Bluetooth, Wi-Fi 

5. Wire line modules: USB, TCP/IP 

 Data Signal Processing 

1. Employed in applications like speech coding, transmission applications, etc 

2. A digital hearing aid example of an embedded system 

 Monitoring 

1. All embedded products coming under the medical domain are with monitoring functions 

2. Electro Cardiogram machine: used for the monitoring of heartbeats of a patient. 

3. Eg: Digital CRO, DMM 

 Control 

1. Contains both sensors and actuators (a device that causes a machine or other device to operate.) 

2. Sensors are connected to the input port while actuators are connected to the output port.

 3. Air conditioner system used to control the room temperature Core of Embedded System 

  Embedded systems are domain and application specific and are built around a central core.

  The core of an Embedded system falls into any of the following categories:-

1. General Purpose & Domain Specific. 

2. Application Specific. 

3. Programmable logic devices.

General Purpose & Domain-specific Processors :-

  Microprocessor 

1. Has all the functional components of CPU on a single silicon chip designed using microelectronics technology 

2. Main purpose of µP is to read data, perform extensive calculations on data, and store those calculations in a mass storage device

3. The Programs used by the µP are stored in the RAM.

Harvard Architecture:-

 It is a computer architecture with physically separate storage and signal pathways for instructions and data. 

 Requires dedicated buses for each of them. 

 Instructions and operands can be fetched simultaneously.

Von –Neumann Architecture:-

 It is a computer design model that uses a processing unit and a single separate storage structure to hold both instructions and data.

 It is named after mathematician and early computer scientist John Von – Neumann. 

 Instructions and data can not be fetched simultaneously.

Microcontrollers:-

 A microcontroller is a compact integrated circuit designed to govern a specific operation in an embedded system. 

 The main use of µC is to control the operation of a machine using a fixed program that is stored in ROM. 

 µC is a compact version of a microcomputer and it is an application-specific system.

 The instruction set of µC can be RISC and CISC. RISC µC 

 RISC: Reduced Instruction Set Computers. 

 It is a CPU design strategy based on simple instructions and fast performance. 

 RISC is a small or reduced set of instructions. Here each instruction is meant to achieve very small tasks. 

 Each instruction is of the same length. 

 Most instructions are completed in one machine cycle. 

 RISC is a microprocessor that is designed to carry out a few instructions at the same time.  

CISC µC:-

  CISC: Complex Instruction Set Computers 

  It is a CPU design strategy based on single instructions which are capable of performing multi-step operations. 

  It has a large number of complex instructions which take a long time to execute. 

  Most instructions are completed in 2 to 10 machine cycles. 

  CISC is considered less efficient than RISC.

DIFFERENCE BETWEEN RISC AND CISC:-

Digital Signal Processors:-

 DSPs are powerful special-purpose 8/16/32-bit microprocessors designed to meet the computational demands and power constraints of today’s ES. 

 They are 2 to 3 times faster than general-purpose microprocessors. 

 DSP implements the speed-up execution of the algorithm in hardware. 

Programmable logic devices(PLDs) 

 ➢ A PLD is an electronic component and it is used to construct reconfigurable digital circuits. 

➢ A logic device has a fixed function but a PLD does not have a defined function at the time of manufacture. 

➢ PLDs can be reconfigured to perform any number of various functions at any time. 

➢ PLDs offer customers a wide range of logic capacity, features, speed, and voltage characteristics.

Types of Pld:-

1) CPLD(Complex PLD) 

 Offer a much smaller amount of logic up to 10000 gates. 

 It has very predictable timing characteristics. 

 It requires low amounts of power 

2) FPGA(Filed Programmable Gate Array) 

 It offers the highest amount of performance as well as the highest logic density 

 They are used in a variety of applications ranging from data processing and storage to instrumentation, telecommunication,  and digital signal processing.

COTS:-

 Commercial Off the shelf components 

 COTS products are products that are commercially available to the general public with published pricing and specifications. 

 They are developed around a general purpose and are readily available in the market and they are cheap. 

 Eg: remote-controlled toy car control units. 

Advantages :

 Ready to use 

 Easy to integrate 

 Reduces development time.

 Disadvantages: 

 No operational or manufacturing standard 

 The vendor or manufacturer may discontinue production of a particular product.

Endianness 

➢ It specifies the order in which the data is stored in the memory by processor operations in a multi-byte system. 

➢ Based on Endianness processors can be of two types:-

 1. Little Endian Processor 2. Big Endian Processor.

➢ Little Endian Processor 

➢ Little-endian means lower order data byte is stored in memory at the lowest address and the higher order data byte at a higher address 

➢ Big Endian Processor 

➢ Big–endian means lower order data byte is stored in memory at the highest address and the higher order data byte at the lowest address.

Sensors:-

 A sensor is used for taking input. 

 It is a transducer that converts one form of energy to another for any measurements or control purpose 

 Eg: temperature sensor, ECG machine Actuators 

 It is used for output. 

 It is a transducer that may be either mechanical or electrical which converts signal to corresponding physical actions. 

 Eg: LEDs, Motors, Relays. 

LED: Light Emitting Diode:-

 It is a p-n junction diode and contains a cathode and anode 

 For functioning, the anode is connected to the positive while the cathode is connected to the negative terminal of the power supply. 

 The maximum current flowing through LED is limited by connecting the resistor in series between the power supply and LED. 

Relays:-

 It basically works as a switch. 

 It is used instead of switches because of several of their advantages over mechanical switches. 

 They are commonly found in automatic control applications as they can control equipment with the help of electrical signals. 

 It is also used in telephone exchanges to switch the calls. 

Communication Interface:-

Communication is the most important part of an embedded system. 

 It is always needed to send or receive data among a chip or between the chips in an embedded system.  8051 has both serial and parallel communication. 

 Parallel communication is achieved by ports whereas serial communication is done through RXD and TXD pins of UART.

Communication Interface used in ES:-

 Onboard communication interface 

 These are used for internal communication of the Embedded System. i.e. communication between different components present in the system. 

 Examples 

 Inter integrated circuit (I2C) 

 Serial Peripheral Interface(SPI) 

 Universal asynchronous Receiver Transmitter(UART) 

 1- wire interface.

 Parallel interface.

External or Peripheral Communication Interface:

 These are used for external communication of the embedded system i.e. communication of different components present in the system with external or peripheral devices. 

 Examples 

 RS 232 

 USB (Universal Serial Bus) 

 Bluetooth 

 Wi-Fi 

 Zig Bee 

 General Packet Radio Service(GPRS) 

Quality Attributes of ES:-

 Attributes: deciding factor about the quality of an ES There are two types of attributes 

 Operational Quality Attributes Related to the Functioning of an ES 

 Non- operational Quality Attributes Not related to the functioning of an ES Operational Attributes 

 Response: how fast 

 Throughput: efficiency 

 Reliability: Rely on functioning 

 Maintainability: support and maintenance 

 Security: Confidentiality, Integrity , Availability 

 Safety.

  Nonoperational Attributes:-

 Testability and Debug ability 

 Evolvability: product can be modified to take advantage of new firmware or hardware 

 Portability: capable of performing operations in any environment 

 Time to porotype and Market: time between the concept of the product and ready to sell 

 Per unit and Total cost.