INTRODUCTION
1.1 INTERNET OF THINGS
Internet of Things is the network of physical objects comprising of all the devices, vehicles, buildings and the other items embedded with electronics, software and sensors which enables these objects to collect and exchange data among each other. Using this technology, objects are sensed and controlled remotely across existing network infrastructure. This creates opportunities for direct integration of the physical world into computer-based systems. IoT has its advantages in saving time as well as work. Applications of IoT include a vast number of systems, among them, a few are Smart homes, Automated car, Automated doors, Automated Escalators, Automated Hand Dryer. Similarly IoT plays a major role in health monitoring system. Whenever a saline is fed to any patient, He/she needs to be constantly monitored by a nurse or any relatives. Unfortunately patient attender may forget, to change the saline bottle as soon as it is totally consumed. Just after the saline finishes, blood rushes back to the saline bottle due to difference in blood pressure and pressure inside the empty saline bottle. This may cause backflow of blood to saline bottle from their vein. This result in the reduction of hemoglobin level of patients and may also lead to shortage of red blood cells in the patient’s blood causing tiredness. To overcome this critical situation, a microcontroller based automatic alerting and indicating device is proposed. When the glucose level is too low it alerts the nurse through the personal computer mounted at the nurse station.
1.2 MICROCONTROLLER:
A microcontroller is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Program memory in the form of ferroelectric RAM, NOR flash or OTP ROM is also often included on chip, as well as a small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications consisting of various discrete chips. Microcontrollers are used in various automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes. Mixed signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems. In the context of the internet of things, microcontrollers are an economical and popular means of data collection, sensing and actuating the physical world as edge devices. Some microcontrollers may use four-bit words and operate at frequencies as low as 4 kHz, for low power consumption (single-digit milli watts or microwatts). They generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt; power consumption while sleeping (CPU clock and most peripherals off) may be just nano watts, making many of them well suited for long lasting battery applications. Other microcontrollers may serve performance-critical roles, where they may need to act more like a digital signal processor (DSP), with higher clock speeds and power consumption.
1.2.1 CLASSIFICATION OF MICROCONTROLLERS:
Microcontrollers are classified based on:
A. Number of bits
1. 8-bit
2. 16-bit
3. 32-bit
B. Memory
1. Embedded memory microcontroller
2. External memory microcontroller
C. Instruction set
1. CISC
2. RISC
D. Architecture
1. Harvard memory architecture microcontroller
2. Princeton memory architecture microcontroller
8-BIT
In 8-bit microcontroller, the point when the internal bus is 8-bit then the ALU is performs the arithmetic and logic operations. The examples of 8- bit microcontrollers are Intel 8031/8051, PIC1x and Motorola MC68HC11 families.
16-BIT:
The 16-bit microcontroller performs greater precision and performance as compared to 8-bit. For example 8 bit microcontrollers can only use 8 bits, resulting in a final range of 0×00 – 0xFF (0-255) for every cycle. In contrast, 16 bit microcontrollers with its 16 bit data width has a range of 0×0000 – 0xFFFF (0-65535) for every cycle. A longer timer most extreme worth can likely prove to be useful in certain applications and circuits. It can automatically operate on two 16 bit numbers.
32-BIT:
The 32-bit microcontroller uses the 32-bit instructions to perform the arithmetic and logic operations. These are used in automatically controlled devices including implantable medical devices, engine control systems, office machines, appliances and other types of embedded systems. Some examples are Intel/Atmel 251 family, PIC3x.
EMBEDED MEMORY CONTROLLER:
When an embedded system has a microcontroller unit that has all the functional blocks available on a chip is called an embedded microcontroller. For example, 8051 having program & data memory, I/O ports, serial communication, counters and timers and interrupts on the chip is an embedded microcontroller.
EXTERNAL MEMORY CONTROLLER:
When an embedded system has a microcontroller unit that has not all the functional blocks available on a chip is called an external memory microcontroller. For example, 8031 has no program memory on the chip is an external memory microcontroller.
CISC:
CISC is a Complex Instruction Set Computer. It allows the programmer to use one instruction in place of many simpler instructions.
RISC:
The RISC is stands for Reduced Instruction set Computer, this type of instruction sets reduces the design of microprocessor for industry standards. It allows each instruction to operate on any register or use any addressing mode and simultaneous access of program and data.
HARVARD MEMORY ARCHITECTURE:
The point when a microcontroller unit has a dissimilar memory address space for the program and data memory, the microcontroller has Harvard memory architecture in the processor.
PRINCETON MEMORY ARCHITECTURE:
The point when a microcontroller has a common memory address for the program memory and data memory, the microcontroller has Princeton memory architecture in the processor.
1.2.2 TYPES OF MICROCONTROLLERS:
1. Microcontroller 8051
2. Renasas Microcontroller
3. AVR Microcontroller
4. PIC Microcontroller
1.2.2.1 MICROCONTROLLER 8051:
It is a 40pin microcontroller with Vcc of 5V connected to pin 40 and Vss at pin 20 which is kept 0V. And there are input and output ports from P1.0 – P1.7 and which having open drain feature. Port3 has got extra features. Pin36 has open drain condition and pin17 has internally pulled up transistor inside the microcontroller. When we apply logic 1 at port1 then we get logic 1 at port21 and vice versa. The programming of microcontroller is dead complicate. Basically we write a program in C-language which is next converted to machine language understand by the microcontroller. A RESET pin is connected to pin9, connected with a capacitor. When the switch is ON, the capacitor starts charging and RST is high. Applying a high to the reset pin resets the microcontroller. If we apply logic zero to this pin, the program starts execution from the beginning.
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