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1. INTRODUCTION
In olden days the industrial environment used to monitor completely by human beings. The efficiency of the industrial environment output depends on the efficiency of the human beings. The efficiency used to be very less because the accurate monitoring cannot be done by the humans. There are some industries where the human cannot go and monitor the process. For example in automobile in anti-breaking system, tetra packing system where pressure is to be accurately measured. This lead to the invention of protocols in industries for automatic monitoring without the intervention of humans.
The protocols are mainly classified into three types. They are:
• Control Area Network (CAN)
• Serial Peripheral Interface (SPI)
• Inter Integrated Circuit (I2C)
CAN: CAN protocol comes into exist to serve the purpose of monitoring in industries. CAN means Control Area Network which communicates the data with 8 wires. The data transfer speed in CAN is 1Mbps.Mainly the industries will not only be built with one application but with many so that the protocol chosen should serve the monitoring for more than one application at a time.
Mainly the protocol in this industries first gather the data by taking the different inputs in the interior industrial areas and then gives to the master which monitors all the inputs that are given to it generally the protocol transfers the data from slaves to master which in turn master monitors the CAN protocol can support up to 15 slaves with single master at a time. The wires used in these protocols as a base station. The main disadvantage of CAN is it is a 8 wire protocol.
SPI: The second protocol that overcomes some disadvantages of CAN is SPI. SPI means Serial Peripheral Interface which communicates the data with 4 wires and with full duplex capability SPI is having same as that of the CAN speed. In this the complexity in programming is reduced compared to CAN because less no. of wires are used in it. Here in this protocol also the master supports only 15 slaves but with full duplex capability that reduces the time of transmission between master and slaves.
The main disadvantage of the usage of these two protocols is occurrence of false data, because there is no acknowledgement. Hence due to this the data cannot be transmitted accurately between the master and slave, that may cause the damage to the application with incorrect communication. Hence the monitoring may fail in some of the cases due to the false data occurrence this disadvantage and less accuracy lead to the invention of I2Cprotocol in the industrial automation.
I2C: This project is based on I2Cprotocol because of its accuracy and reduction of false data occurrence. Mainly the I2C protocol provides multi-master capability. The slaves supported by multi-master are 128 slaves due to this advantage of I2C it communicate with many applications at a time the I2C protocol uses only two wires SDA and SCL for serial data and serial clock respectively. The wires used in SPI looks like a central hub with usage of less wires than that of CAN.
The I2C protocol communication looks like the wires of power supply that we provide to home hence due to the usage of less wires the programming complexity is also less the accuracy is very high such that the I2Cis used in critical industrial applications. The project mainly makes use of sensors for accurately sensing patterns all these sensors are provided as inputs to slave and then the communication between master and slave is done through I2Cprotocol.
2. EMBEDDED SYSTEM
The development of microcontrollers caused the explosion of embedded systems in the 1980s. In earlier days,8 bit controllers are used in the most of the systems, because the 16 and 32 bit microcontrollers had many disadvantages like development tools were expensive, devices were large, power hungry and difficult to integrate into a design devices had tight electrical and timing constraints.
However, things have changed. Today, prices have dropped substantially, cheap, mature development tools are available, better features, more memory. The power of 32 bit devices opens up many applications where embedded systems were previously too slow. So, many new systems are using 16 and 32 bit Processors.
During the 1970s, the defence industry was the driving force behind embedded system development. Today, development is driven by a much wider group of industries.
2.1 EMBEDDED SYSTEMS
An embedded system is a computer system designed to perform one or a few dedicated functions, often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal computer (PC), is designed to be flexible and to meet a wide range of end-user needs. Embedded systems control many devices in common use today.
Embedded systems are controlled by one or more main processing cores that are typically either microcontrollers or digital signal processors (DSP). The key characteristic, however, is being dedicated to handle a particular task, which may require very powerful processors.
Since the embedded system is dedicated to specific tasks, design engineers can optimize it to reduce the size and cost of the product and increase the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale. An embedded system used in a device is programmable by the designer of the system and generally cannot be programmed by the end user.
2.2 CHARACTERISTICS OF EMBEDDED SYSTEMS
RELIABILITY: Embedded systems should be very reliable since they perform critical functions. 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.
RESPONSIVENESS: Embedded systems should respond to events as soon as possible. For example, a patient monitoring system should process the patient’s heart signals quickly and immediately notify if any abnormality in the signals is detected.
SPECIALISED HARDWARE: Since embedded systems are used for performing specific functions, specialized hardware is used. For example, embedded systems that monitor and analyze audio signals use signal processors.
LOW COST: As embedded systems are extensively used in consumer electronic systems, they are cost sensitive. Thus their cost must be low.
ROBUSTNESS: Embedded systems should be robust since they operate in a harsh environment. They should endure vibrations, power supply fluctuations and excessive heat. Due to limited power supply in an embedded system, the power consumed by the components of the embedded system should be kept to a minimum.
2.3 REAL TIME SYSTEMS
Embedded systems are often confused with real-time systems. A real-time system is one in which the correctness of the computations not only depends on the accuracy of the result, but also on the time when the result is produced. This implies that a late answer is a wrong answer. A hard real-time system should always respond to an event within the deadline or else the system fails. Soft real-time systems have less severe time constraints. All embedded systems are not real-time systems and vice-versa.
2.4 CLASSIFICATION OF EMBEDDED SYSTEMS
Embedded systems can be classified into three types:
SMALL SCALE EMBEDDED SYSTEMS: These systems are designed with a single 8- or 16-bit microcontroller; they have little hardware and software complexities and involve board-level design. They may even be battery operated. When developing embedded software for these, an editor, assembler and cross assembler, specific to the microcontroller or processor used, are the main programming tools. Usually, ‘C’ is used for developing these systems. ‘C’ program compilation is done into the assembly, and executable codes are then appropriately located in the system memory. The software has to fit within the memory available and keep in view the need to limit power dissipation when system is running continuously.
MEDIUM SCALE EMBEDDED SYSTEMS: These systems are usually designed with a single or few 16- or 32-bit microcontrollers or DSPs or Reduced Instruction Set Computers (RISCs). These have both hardware and software complexities. For complex software design, these are the following programming tools: RTOS, Source code engineering tool, Simulator, Debugger and Integrated Development Environment (IDE). Software tools also provide the solutions to the hardware complexities. An assembler is of little use as a programming tool. These systems may also employ the readily available ASSPs and IPs for the various functions like bus interfacing, encrypting, deciphering, discrete cosine transformation and inverse transformation, TCP/IP protocol stacking and network connecting functions.
SOPHISTICATED EMBEDDED SYSTEMS: Sophisticated embedded systems have enormous hardware and software complexities and may need scalable processors or configurable processors and programmable logic arrays. They are used for cutting edge applications that need hardware and software co-design and integration in the final system; however, they are constrained by the processing speeds available in their hardware units. Certain software functions such as encryption and deciphering algorithms, discrete cosine transformation and inverse transformation algorithms, TCP/IP protocol stacking and network driver functions are implemented in the hardware to obtain additional speeds by saving time. Some of the functions of the hardware resources in the system are also implemented by the software. Development tools for these systems may not be readily available at a reasonable cost or may not be available at all.