Abstract:
We can use wireless RF links to connect two PCs through serial port to communicate to each other. The coding is in C to chat between two PCs or send a file through RF Link at the distance of approx. 10 meters.

ABSTRACT

In this project work the basic and essential concepts of radio communication were utilized to create a wireless communication channel between two Computers. One computer is placed at the transmitter section. In this section we can see the display of the parameter values. The second computer is placed at the receiving end, where the maintenance persons are monitoring the system. Here we can monitor the parameters condition continuously. A PIC micro-controller (16f877A) and MAX232, RS232 are used as interfacing units between the system and RF transmitter and also at the receiver section.
The program code is written in Assembly language and the serial communication concept is used to transfer the data. This project can be used as an alternate to wireless communication.
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1. INTRODUCTION

The project report describes on the design development and fabrication of one demo unit of the project work “Implementation of wireless communication between computers”.
Now a day, with the advancement technology, particularly in the field of Micro-controllers, all the activities in our daily living have become a part of Information Technology and we find micro-controllers in each and every application. Thus, trend is directing towards Microcontrollers Based Project works. However, in this project work, the transferring of data serially is monitored. Subsequently, after serial processing, these signals are encoded. This information is transmitted through RF transmitter. The received information (using suitable RF receiver) is again decoded into digital signal at the receiver end. Then the decisions are taken with the help of micro-controllers and associated software.
The micro-controller block is playing a major role in this project work. The Micro-controller chip is used in this project work is PIC 16f877A, and this is like heart of the project work. The PIC micro-controller is 40 pin IC.
Micro controllers are “embedded” inside some other device so that they can control the features or actions of the product. Another name for a micro-controller, therefore, is “Embedded Controller”. Micro controllers are dedicated to one task and run one specific program. The program is stored in ROM (read only memory) and generally does not change. Micro controllers are often low-price devices. A battery operated micro-controller might consume 50 mille watts. A micro-controller has a dedicated input device and often (but not always) has a small LED or LCD display for output. A micro-controller also the input from the device it is controlling and controls the device by sending to different components in the device.
Now coming to the project work, to obtain the parameter (transferring of data serially between to computers) from transmitter to the receiver, where the serial data transfer is monitored, the radio transmission technique is incorporated in the design. For this Radio transmission, there are number of mechanisms by which Radio waves may travel from a transmitting to a receiving antenna. The terms, GROUND WAVES, SKY WAVES and SCOPE or TROPOSHERIC WAVES designates the more important of these.
The ground wave can exist when the transmitting and receiving are close to surface of the earth and are vertically polarized. The sky wave represents that reaches receiving antenna as a result of a bending of the wave path introduced by the ionization in the upper atmosphere. The space wave represents energy that travels from the transmitting to the receiving antenna in the earth troposphere. The radio transmission at frequencies above about 30MHz is normally the space wave propagation. The transmitters that are frequency modulated find extensive use at frequencies use at frequencies above 40MHz.

1.1 EMBEDDED SYSTEMS:
A system is something that maintains its existence and functions as a whole through the interaction of its parts. E.g. Body, Mankind, Access Control, etc A system is a part of the world that a person or group of persons during some time interval and for some purpose choose to regard as a whole, consisting of interrelated components, each component characterized by properties that are selected as being relevant to the purpose.

• Embedded System is a combination of hardware and software used to achieve a single specific task.
• Embedded systems are computer systems that monitor, respond to, or control an external environment.
• Environment connected to systems through sensors, actuators and other I/O interfaces.
• Embedded system must meet timing & other constraints imposed on it by environment.


An embedded system is a microcontroller-based, software driven, reliable, real-time control system, autonomous, or human or network interactive, operating on diverse physical variables and in diverse environments and sold into a competitive and cost conscious market. An embedded system is not a computer system that is used primarily for processing, not a software system on PC or UNIX, not a traditional business or scientific application. High-end embedded & lower end embedded systems. High-end embedded system - Generally 32, 64 Bit Controllers used with OS. Examples Personal Digital Assistant and Mobile phones etc. Lower end embedded systems - Generally 8,16 Bit Controllers used with a minimal operating systems and hardware layout designed for the specific purpose. Examples Small controllers and devices in our every day life like Washing Machine, Microwave Ovens, where they are embedded in.

2. DETAILS ABOUT RADIO FREQUENCIES

2.1 Radio Frequencies
A radio wave is an electromagnetic wave propagated by an antenna. Radio waves have different frequencies, and by tuning a radio receiver to a specific frequency you can pick up a specific signal.

Radio is a technology that allows the transmission of signals by modulation of electromagnetic waves with frequencies those of light.
In today’s economy, people are demanding more and more mobility to function efficiently. To address this demand, companies are moving data by air instead of wire. There are many applications in which it is more efficient to move data wirelessly. For this reason, it is necessary to make communications between two PC’s as easy as possible by allowing people to move computers without moving wires. A communication client program will interface with the user’s PC to send data to the wireless data link. On the opposing end, a different user will use the second communications program to receive the data from their data link. The data itself will be sent by RF waves from a transmitter device to a receiver device. The RF transmission will be transparent to the users PC’s as if they were directly connected to each other using a RS232 crossover cable.

2.2 Implementation
To implement the wireless RS232 interface two different circuit boards will be designed. The two boards will consist of a transmitter and receiver. The transmitter will accept data from a RS232 (9-pin) of a PC port and transfer the information to RF signal. The receiver will capture the RF signal, transferring it back to a digital signal, and finally import it into the RS232 (9-pin) port of a PC. The purpose of the rest of this document is to specify the integration of this RF technology.
2.3 Units
As the unit of frequency is the hertz (Hz), frequencies shall be expressed:
- in kilohertz (kHz), up to and including 3000 kHz;
- in megahertz (MHz), above 3 MHz, up to and including 3000 MHz;
- in gigahertz (GHz), above 3 GHz, up to and including 3000 GHz.

3. DETAILS ABOUT MICROCONTROLLER
The micro-controller is a chip, which has a computer processor with all its support function, memory (both program storage and RAM), and I/O built in to the device. These built in functions minimize the need for external circuits and devices to design in the final applications.
Most microcontrollers do not require a substantial amount of time to learn how to efficiently program them, although many of then which have quirks which you will have to understand before you attempt to develop your first application.
Along with micro-controllers getting faster, smaller and more power efficient they are also getting more and more features. Often, the first version of micro-controller will just have memory and digital I/O, but as the device family matures, more and more pat numbers with varying features will be available.
With all the 8052 manufactures products taken into the account, there are over two hundred different 8052 part numbers, each with different features and capabilities. For most applications, we will be able to find a device within the family that meets our specifications with a minimum of external devices, or an external but which will make attaching external devices easier, both in terms of wiring and programming.
For many micro controllers, programmers can be built very cheaply, or even built in to the final application circuit eliminating the need for a separate circuit. Also simplifying this requirement is the availability of micro-controllers with SRAM and EEPROM for control store, which will allow program development without having to remove the micro controller from the application circuit.

4.1 DESCRIPTION OF THE BLOCK DIAGRAM


The Block diagram of the project work “Implementation of Wireless Communication between two Computers” is explained. For better understanding, the total block diagram is divided into two various blocks and each block explanation is provided in this chapter. The complete block diagram consists of the following blocks.
 Functional Units
 MAX232 Connector
 Power Supply
 Reset
 Micro-controller
 Encoder-Buffer
 Decoder- Buffer
 Serial Interface
 Transmitter
 Receiver
 Antenna
4.1.1 Functional Units
The above figure conceptually displays the proposed system architecture for our project. Each box represents a different functional unit. Each box will be described below to give the reader a better understanding of this system.


4.1.2 MAX232 Connector
The MAX232 connector will be used to transfer data from the MAX232 (16-pin) port of a PC to the input line converter. The connector will be a 90-degree flat mount design that will allow the pins of a serial connection to be transferred to data lines in a PC board. A typical model would be 182-09F-ND Right Angle D-Sub connector made by Norcomp.
4.1.3 Power Supply
The AC main Block is the power supply which is of single phase 230V ac. This should be given to step down transformer to reduce the 230V ac voltage to low voltage. i.e., to 6V or 12V ac this value depends on the transformer inner winding. The output of the transformer is given to the rectifier circuit. This rectifier converts ac voltage to dc voltage. But the voltage may consist of ripples or harmonics.
To avoid these ripples the output of the rectifier is connected to filter. The filter thus removes the harmonics. This is the exact dc voltage of the given specification. But the controller operates at 5V dc and the relays and driver operates at 12V dc voltage. So we need a regulator to reduce the voltage. 7805 regulator produces 5V dc and 7812 regulator produces 12V dc. Both are positive voltages.
4.1.4 Reset
The dual button switch will allow the user to start, stop, and reset the device as they see fit. It will also have a data line going to the led to indicate if the circuit is on/Off.
4.1.5 Micro Controller
Micro controller is a true computer on a chip the design incorporates all of the features found in a microprocessor CPU: arithmetic and logic unit, stack pointer, program counter and registers. It has also had added additional features like RAM, ROM, Serial I/O, counters and clock circuit.
4.1.6 Encoder-Buffer
The Encoder-Buffer is to be designed to condition the signal for the transmitter by adding error detection and encoding. i.e. how 0’s and 1’s will be declared. One proposal for is to use Manchester encoding. Manchester encoding uses logic of a high to low as 0 and low to high as a 1. That implies that every bit period is divided into two and insures that the transaction from high to low or low to high is in the middle of each period. By creating this phenomenon we allow the transmitter to synchronize with the receiver at every bit. With this we will be able to maximize reliability and implement techniques to assist in error detection.
4.1.7 Decoder-Buffer
The Decoder-Buffer is to be designed to condition the signal for the receiver by checking for errors and reproducing the 1’s and 0’s by implementing the same logic as the encoder. The decoder-buffer will synchronize with the encoder-buffer reading the information, checking fore errors and sending it on to the serial interface.
4.1.8 Serial Interface
The serial interface on the transmitter will accept a data line from the MAX 232 connector and transfer it to TTL/CMOS standard logic level. The TTL/CMOS signal will then be sent on a data line to the Encoder/Buffer. The serial interface on the receiver will accept a data from the Decoder/Buffer and transfer it to TTL/CMOS standard logic level. The TTL/CMOS signal will then be sent on a data line to the MAX232 Connector.

4.1.9 Transmitter
The transmitter will be an AM hybrid transmitter that operates at a frequency of 433.92 MHz. The transmitter accepts a TTL/CMOS signal on a data line from the Encoder/Buffer and will output a signal to an antenna. The proposed transmitter is manufactured in Italy by Telecontrolli s.p.a and supplied by Okwelectronics; part number AMRT4-433.
4.1.10 Receiver
The receiver will be a AM SuperRegen Receiver Module that operates at a frequency of 433.92MHz. The receiver accepts a signal from an antenna and will output TTL/CMOS signal on a data line to the Decoder/Buffer. The proposed receiver is manufactured in Italy by Telecontrolli s.p.a and supplied by Okwelecronics; part number AMHRR3-433.
4.1.11 Antenna
User defined depending on required signal distance / power.

Get the report here:
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please ...

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