PAGE 45

Design and Implementation of ZIGBEE Based BillboardTABLE OF CONTENTS

CHAPTER

TITLE

PAGE NO

ABSTRACT

5

1.

INTRODUCTION

5

1.1 Block Diagram

6

1.2 Circuit Diagram

6

2.

HARDWARE DESCRIPTION

2.1Introduction

7

2.2Description

72.2.1Memory Unit

8

2.2.2Central Processing Unit

9

2.2.3Input Output Unit

10

2.2.4Serial communication

11

2.2.5Timer Unit

13

2.2.6AT89C51 MICROCONTROLLER

14

2.2.7Description

14

2.2.8Special Function Registers

153.

MICROCONTROLLER INTERFACING

3.1 BILLBOARD

3.1.1The EN control line

21

3.1.2Checking the busy status of BILLBOARD

22

3.1.3Initializing the BILLBOARD

22

3.1.4Clearing the Display

23

3.1.5Writing text to the BILLBOARD

24

3.1.6Cursor Positioning

26

3.2ZIGBEE MODULE

3.2.1Key features

28

3.2.2Specifications

29

3.2.3Pin Signals

30

3.2.4Electrical Characteristics

31

3.2.5Flow control

32

3.3RS232 serial connector pin assignment

344.

DESCRIPTION OF DEVELOPMENT SYSTEM

4.1Cross Compilers

35

4.1.1Introduction to Keil

36

4.1.2Functioning of Keil

36

4.1.3Development tools in keil

374.1.4C51 Optimizing C Cross Compiler

38

4.1.5A51 Macro Assembler

39

4.1.6BL51 Code Banking Linker/Locator

40

4.1.7OC51 banked object file converter

40

4.1.8OH51 object hex converter

40

4.1.9VISION/51 FOR WINDOWS

414.2TARGET PROCESSOR

425.

APPLICATION SOFTWARE

5.1Application software description

45

5.2Screen Shots

466.

CONCLUSION

46

ABSTRACTThe objective of our project is to design and implement zigbee based Advertising billboard system. Our goals is to design an electronic billboard that can show images, perhaps even animated ones, and is able to receive new ones remotely. This design constructed using super E-paper has to have several features. First, new data should be able to be received. So a receiver is necessary. In order to be able to receive data remotely, some sort of wireless system has to be set up.To process the data accordingly, a controller has to be configured. This controller also has to show the image on a screen. Some sort of micro processing unit is required to do this task.

In the case of a slideshow of images or even an animation, data has to be stored in memory. The choice of what to type of storage to use is an important one as well. It has to be fast enough to both store new data while continuing retrieve data to send to the screen.

LITERATURE REVIEW OVERVIEW XBee and XBee-PRO Modules were engineered to meet ZigBee/IEEE 802.15.4 standards and support the unique needs of low-cost, low-power wireless sensor networks. The modules require minimal power and provide reliable delivery of critical data between devices. The modules operate within the ISM 2.4 GHz frequency band and are pin-for-pin compatible with each other.Key Features:

Long Range Data Integrity:XBee Range

Indoor/Urban: up to 100 (30 m)

Outdoor line-of-sight: up to 300 (100 m)

Transmit Power: 1 mW (0 dBm)

Receiver Sensitivity: -92 dBm

XBee-PRO Range

Indoor/Urban: up to 300 (100 m)

Outdoor line-of-sight: up to 1 mile (1500 m)

Transmit Power: 100 mW (20 dBm) EIRP

Receiver Sensitivity: -100 dBm

RF Data Rate: 250,000Advanced Networking & Security

Retries and Acknowledgements

DSSS (Direct Sequence Spread Spectrum)

Each direct sequence channels has over 65,000 unique network addresses available

Point-to-point, point-to-multipoint and peer-to-peer topologies supported

128-bit Encryption

METHODOLOGYSHORTCOMINGS OF THE EXISTING SYSTEM:

Every bus stop and billboard has a paper advertisement inside. The reason for this is simple; paper is easy to use and extremely cheap. However, it has some drawbacks as well. Before an image is actually on the street, it first has to be printed, pasted and placed. The journey from design to placement is quite long. Another major disadvantage is the considerable amount of waste generated by the use of paper. Finally, many people just ignore a paper advertisement. Their attention is drawn to the vibrant environment around them and not to a still image.PLAN OF IMPLEMENTATION:This project is implemented in various stages mentioned belowSTAGE 1: Implementation of ApplicationSTAGE 2: Implementation of Zigbee Protocol.STAGE 3: Implementation of BILLBOARD displaySTAGE 4: System Integration and TestingSTAGE 1:

An application software is been created to send the data to the microcontroller which is been connected with the billboard. The application software is created by using Microsoft Visual Studio. It will run on the PC and send the data to the microcontroller by using Zigbee transceiver.

STAGE 2:

The Zigbee transmitter at the transmitter side will send the data to the Zigbee receiver which is present at the receiver side. The Zigbee Receiver stores the data in the microcontroller. The received data is displayed in the BILLBOARD screen.STAGE 3: BILLBOARD display has the capacity to display whatever we are promoting in programming for microcontroller if microcontroller sends appropriate commands to it. In our project it displays the status of the mailbox and the operation of our project. BILLBOARD has two ports to be connected with microcontroller, one is for control lines, another one is for data lines, this data lines will carry the data to be displayed in BILLBOARD display and control lines gets the control commands for BILLBOARD in which place data has to display.

STAGE 4:Each and Every part of our project will be integrated as given below,

Zigbee can be connected to the microcontroller to receive data from it. And Microcontroller will be connected with BILLBOARD display, the BILLBOARD used to display the data. This whole section has been tested by giving power supply in it. By using of this project the automatic delivery of mails/couriers can be easily monitored.

1. INTRODUCTION

Outdoor advertising is mainly characterized by the use of paper. Every bus stop and billboard has a paper advertisement inside. The reason for this is simple; paper is easy to use and extremely cheap. However, it has some drawbacks as well. Before an image is actually on the street, it first has to be printed, pasted and placed. The journey from design to placement is quite long. Another major disadvantage is the considerable amount of waste generated by the use of paper. Finally, many people just ignore a paper advertisement. Their attention is drawn to the vibrant environment around them and not to a still image. So not surprisingly, the advertising industry has been searching for years to find an alternative for this kind of advertising. Usually the only alternative that is found is using an BILLBOARD screen with a controller, a so-called digital screen. These can show animated images and can be updated instantly and remotely. This reduces the journey from design to placement to only a couple of minutes. However, digital screens have not been deployed in great numbers. This is because no satisfying products exist thus far. This is due to several problems with the modernization of outdoor advertising. First, it is still too expensive; it is practically impossible to compete with paper on a financial level. Also, since the objects are outside all the time, they are vulnerable to vandalism. Paper posters are easily replaced, but its digital counterpart is quite a lot more expensive when it gets destroyed and needs to be replaced. Lastly, an electronic billboard requires a lot of energy, which is both a waste of money and harmful to the environment.

A possible alternative is super E-paper. Super E-paper has many of the advantages of conventional paper and digital billboards, without many drawbacks. For instance, once a data has been loaded onto super E-paper, it doesnt need to be refreshed anymore. This decreases its energy consumption significantly. Also, just like a digital screen, it can be updated instantly and remotely. Besides this, super E-paper is relatively cheap and has paper-like visibility and flexibility.1.1 BLOCK DIAGRAMTransmitter Section:

The Zigbee and gsm module transceiver is connected with the PC via the serial port. The GUI is run on the PC to get the data from the user. GUI is created by using Microsoft Visual Studio.Receiver Section:

The receiver section has the microcontroller P89V51RD2 is an 8-bit microcontroller which run with the frequency of 11.0592MHz. The Zigbee transceiver is connected with the microcontroller via the serial port. The billboard(BILLBOARD) is connected with the parallel ports of the microcontroller to get the data from the microcontroller. The billboard will display the data which is given in the transmitter side by using the GUI.1.2 CIRCUIT DIAGRAM FOR TRANSMITTER SECTION

CIRCUIT DIAGRAM FOR RECEIVER SECTION:

2. HARDWARE DESCRIPTION

2. HARDWARE DESCRIPTION

2.1 INTRODUCTION TO TARGET PROCESSOR

Microcontroller differs from a microprocessor in many ways. First and the most important is its functionality. In order for a microprocessor to be used, other components such as memory, or components for receiving and sending data must be added to it. In short that microprocessor is the very heart of the computer. On the other hand, microcontroller is designed to be all of that in one. No other external components are needed for its application because all necessary peripherals are already built into it. Thus, we save the time and space needed to construct devices .this chapter deals with the study of microcontrollers.

2.2 DESCRIPTION TO EMBEDDED CONTROLLERS

Microcontroller, as the name suggests, are small controllers. These are like single chip computers that are often embedded into systems to function as processing /controllers unit. For example, the remote control you are using probably has microcontrollers inside that do decoding and other controlling functions. They are also used in automobiles, washing machines, microwave ovens, toysetc, where automation is needed. The key features of microcontrollers include:

High integration of Functionality

Microcontrollers sometimes are called single chip computers because they have on-chip memory and I/O circuitry and other circuitries that enable them to function as small standalone computers without other supporting circuitry.

Field Programmability, Flexibility

Microcontrollers often use EEPROM or EPROM as their storage device to allow field programmability so they are flexible to use. Once the program is tested to be correct then large quantities of microcontrollers can be programmed to be used in embedded systems.

Easy to Use

Assembly language is often used in microcontroller and since they usually follow RISC architecture, the instruction set is small. The development package of microcontrollers often includes an assembler ,a simulator ,a programmer to burn the chip and a demonstration board .Some packages include a high level language compiler such as a C compiler and more sophisticated libraries.

The main units of a microcontroller are discussed below:-

2.2.1MEMORY UNIT

Memory is part of the microcontrollers whose function is to store data.

The easiest way to explain it is to describe it as one big closet with lots of drawers. If we suppose that we marked the drawers in such a way that they cant be confused, any of their contents will then be easily accessible. It is enough to know the designation of the drawer and so its contents will be known to us for sure.

Fig 2.2.1 Memory Unit of Microcontroller

Memory components are exactly like that. For a certain input we get the contents of a certain addressed memory location and thats all. Two new concepts are brought to us: addressing and memory location. Memory consists of all memory locations, and addressing is nothing but selecting one of them. This means that we need to select the desired memory location on one hand, and on the other hand we need to wait for the contents of that location. Besides reading from a memory location, memory must also provide for writing onto it. This is done by supplying an additional line called control line. We will designate this line as R/W (read/write). Control line used in the following way: if r/w=1, reading is done, and if opposite is true then writing is done on the memory location. Memory is the first element, and we need a few operation of our microcontroller.

2.2.2 CENTRAL PROCESSING UNIT

Let add three memory locations to a specific block that will have a built in capability to multiply, divide, subtract, and move its contents from one memory location onto another. The part we just in is called Central Processing Unit (CPU). Its memory locations are called registers.

Fig 2.2.2 Central Processing Unit of Microcontroller

Registers are therefore memory locations whose role is to help with performing various mathematical operations or any other operations with data wherever data can be found. Look at the current situation. We have two independent entities (memory and CPU) which are interconnected, and thus any exchange of data is hindered, as well as its functionality. If, for example, we wish to add the contents of two memory locations and return the result again back to memory, we would need a connection between memory and CPU. Simply stated, we must have some way though data goes from one block to another.

2.2.3 Input-Output Unit

Those locations weve just added are called ports. There are several types of ports: Input, output or bidirectional ports. When working with ports, first of all it is necessary to choose which port we need to work with, and then to send data to, or take it from the port.

Fig 2.2.3 Input-Output Unit of Microcontroller

When working with it the port acts like a memory location. Something is simply being written into or read from it, and it could be noticed on the pins of the microcontroller.

2.2.4 Serial Communication:

Beside stated above weve added to the already existing unit the possibility of communication with an outside world. However, this way of communicating has drawbacks. One of the basic drawbacks is the number of lines which need to be used in order to transfer data. What if it is being transferred to a distance of several kilometers? The number of lines times numbers of kilometers doesnt promise the economy of the project. It leaves us having to reduce the number of lines in such a way that we dont lessen its functionality. Suppose we are working with three lines only, and that one line is used for sending data ,other for receiving, and the third one is used as a reference line for both the input and output side. In order for this to work, we need to set the rules of exchange of data. These rules are called protocol. Protocol is therefore defined in advance so there wouldnt be any misunderstanding between the sides that are communicating with each other. The logical unit 1 is set up on the transmitting line until transfer begins. Once the transfer starts, we lower the transmission line to logical 0 for a period of time (which we will designate as T), so the receiving side will know that it is receiving data, and so it will activate its mechanism for reception. Lets go back now to the transmission side and start putting logic zeros and ones the transmitter line in the order from a bit of the lowest value to a bit of the highest value. Let each bit stay on line for a time period which is equal to T, and in the end, or after the 8th bit. Let us bring the logical unit 1 back on the line which will mark the end of the transmission of one data. The protocol weve just described is called in professional literature NRZ (Non-Return to Zero).

Fig 2.2.4 Serial Communication

As we have separate lines for receiving and sending, it is possible to receiving and sends data at the same time. So called full-duplex mode block which enables this way of communication is called a serial communication block.

Unlike the parallel transmission, data moves here bit by bit, or in a series of bits what defines the term serial communication comes from. After the reception of data we need to read it from the receiving location and store it in memory as opposed to sending where the process is reversed. Data goes from memory through the buys to the sending location, and then to the receiving unit according unit according to the protocol.

2.2.5 Timer Unit

Since we have the serial communication explained, we can receive, send and Process data.

Fig 2.2.5 Timer

However, in order to utilize it in industry we need a few additionally blocks. One of those is the timer block which is significant to us because it can give us information about time, duration, protocol etc. The basic unit of the timer is a free-run counter which is in fact a register whose numeric value increments by one in even intervals, so that by taking its value during periods T1 and T2 and on the basis of their difference we can determine how much time has elapsed. This is a very important part of the microcontroller whose understanding requires most of our time.

2.2.6 FEATURES OF AT89C51 MICROCONTROLLER (TARGET

PROCESSOR) Features: Compatible with MCS-51 Products

4K Bytes of In-System Reprogrammable Flash Memory

Endurance: 1,000 Write/Erase Cycles

Fully Static Operation: 0 Hz to 24 MHz

Three-Level Program Memory Lock

128 x 8-Bit Internal RAM

32 Programmable I/O Lines

Two 16-Bit Timer/Counters

Six Interrupt Sources

Programmable Serial Channel

Low Power Idle and Power Down Modes

DescriptionThe AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is manufactured using Atmels high density nonvolatile memory technology and is compatible with the industry standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications

Pin Configurations

The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.

Pin Description

VCC

Supply voltage.

GND

Ground.

Port 0

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as highimpedance inputs.

Port 0 may also be configured to be the multiplexed loworder address/data bus during accesses to external program and data memory. In this mode P0 has internal pullups.

Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification. External pullups are required during program verification.

Port 1

Port 1 is an 8-bit bidirectional I/O port with internal pullups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pullups. Port 1 also receives the low-order address bytes during Flash programming and verification.

Port 2

Port 2 is an 8-bit bidirectional I/O port with internal pullups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pullups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this application it uses strong internal pull-ups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some

control signals during Flash programming and verification.

Port 3

Port 3 is an 8-bit bidirectional I/O port with internal pullups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups. Port 3 also serves the functions of various special features of the AT89C51 as listed below:

Port 3 also receives some control signals for Flash programming and verification.

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.

ALE/PROG

Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming.

In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may be used for external timing or clocking purposes. Note, however, that one ALE

pulse is skipped during each access to external Data Memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.

PSENProgram Store Enable is the read strobe to external program memory When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine

cycle, except that two PSEN activations are skipped during each access to external data memory.

EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH.

Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.

EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming, for parts that require 12-volt VPP.XTAL1Input to the inverting oscillator amplifier and input to the internal clock operating circuit.XTAL2

Output from the inverting oscillator amplifier.Oscillator Characteristics

XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2.

There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.

Idle Mode

In idle mode, the CPU puts itself to sleep while all the onchip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special

functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardware reset. It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution,

from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to

the port pins is not inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction following the one that invokes Idle

should not be one that writes to a port pin or to external memory.

3. MICROCONTROLLER INTERFACING3.1. BILLBOARD:

Frequently, an 8051 program must interact with the outside world using input and output devices that communicate directly with a human being. One of the most common devices attached to an 8051 is a BILLBOARD display. Some of the most common BILLBOARDs connected to the 8051 are 16x2 and 20x2 displays. This means 16 characters per line by 2 lines and 20 characters per line by 2 lines, respectively.

Fortunately, a very popular standard exists which allows us to communicate with the vast majority of BILLBOARDs regardless of their manufacturer. The standard is referred to as HD44780U, which refers to the controller chip which receives data from an external source (in this case, the 8051) and communicates directly with the BILLBOARD.

44780 BACKGROUND

The 44780 standard requires 3 control lines as well as either 4 or 8 I/O lines for the data bus. The user may select whether the BILLBOARD is to operate with a 4-bit data bus or an 8-bit data bus. If a 4-bit data bus is used the BILLBOARD will require a total of 7 data lines (3 control lines plus the 4 lines for the data bus). If an 8-bit data bus is used the BILLBOARD will require a total of 11 data lines (3 control lines plus the 8 lines for the data bus).

The three control lines are referred to as EN, RS, and RW.

The EN line is called "Enable." This control line is used to tell the BILLBOARD that you are sending it data. To send data to the BILLBOARD, your program should make sure this line is low (0) and then set the other two control lines and/or put data on the data bus. When the other lines are completely ready, bring EN high (1) and wait for the minimum amount of time required by the BILLBOARD datasheet (this varies from BILLBOARD to BILLBOARD), and end by bringing it low (0) again.

The RS line is the "Register Select" line. When RS is low (0), the data is to be treated as a command or special instruction (such as clear screen, position cursor, etc.). When RS is high (1), the data being sent is text data which sould be displayed on the screen. For example, to display the letter "T" on the screen you would set RS high.

The RW line is the "Read/Write" control line. When RW is low (0), the information on the data bus is being written to the BILLBOARD. When RW is high (1), the program is effectively querying (or reading) the BILLBOARD. Only one instruction ("Get BILLBOARD status") is a read command. All others are write commands--so RW will almost always be low.

Finally, the data bus consists of 4 or 8 lines (depending on the mode of operation selected by the user). In the case of an 8-bit data bus, the lines are referred to as DB0, DB1, DB2, DB3, DB4, DB5, DB6, and DB7.

AN EXAMPLE HARDWARE CONFIGURATION

As we've mentioned, the BILLBOARD requires either 8 or 11 I/O lines to communicate with. For the sake of this tutorial, we are going to use an 8-bit data bus--so we'll be using 11 of the 8051's I/O pins to interface with the BILLBOARD.

Let's draw a sample psuedo-schematic of how the BILLBOARD will be connected to the 8051.

As you can see, we've established a 1-to-1 relation between a pin on the 8051 and a line on the 44780 BILLBOARD. Thus as we write our assembly program to access the BILLBOARD, we are going to equate constants to the 8051 ports so that we can refer to the lines by their 44780 name as opposed to P0.1, P0.2, etc. Let's go ahead and write our initial equates:

DB0 EQU P1.0DB1 EQU P1.1DB2 EQU P1.2DB3 EQU P1.3DB4 EQU P1.4DB5 EQU P1.5DB6 EQU P1.6DB7 EQU P1.7EN EQU P3.7RS EQU P3.6RW EQU P3.5DATA EQU P13.3.1 HANDLING THE EN CONTROL LINE

As we mentioned above, the EN line is used to tell the BILLBOARD that you are ready for it to execute an instruction that you've prepared on the data bus and on the other control lines. Note that the EN line must be raised/lowered before/after each instruction sent to the BILLBOARD regardless of whether that instruction is read or write, text or instruction. In short, you must always manipulate EN when communicating with the BILLBOARD. EN is the BILLBOARD's way of knowing that you are talking to it. If you don't raise/lower EN, the BILLBOARD doesn't know you're talking to it on the other lines.

Thus, before we interact in any way with the BILLBOARD we will always bring the EN line low with the following instruction:

CLR ENAnd once we've finished setting up our instruction with the other control lines and data bus lines, we'll always bring this line high:

SETB ENThe line must be left high for the amount of time required by the BILLBOARD as specified in its datasheet. These are normally on the order of about 250 nanoseconds, but check the datasheet. In the case of a typical 8051 running at 12 MHz, an instruction requires 1.08 microseconds to execute so the EN line can be brought low the very next instruction. However, faster microcontrollers (such as the DS89C420 which executes an instruction in 90 nanoseconds given an 11.0592 Mhz crystal) will require a number of NOPs to create a delay while EN is held high. The number of NOPs that must be inserted depends on the microcontroller you are using and the crystal you have selected.

The instruction is executed by the BILLBOARD at the moment the EN line is brought low with a final CLR EN instruction.

3.3.2 CHECKING THE BUSY STATUS OF THE BILLBOARDAs previously mentioned, it takes a certain amount of time for each instruction to be executed by the BILLBOARD. The delay varies depending on the frequency of the crystal attached to the oscillator input of the 44780 as well as the instruction which is being executed.

While it is possible to write code that waits for a specific amount of time to allow the BILLBOARD to execute instructions, this method of "waiting" is not very flexible. If the crystal frequency is changed, the software will need to be modified. Additionally, if the BILLBOARD itself is changed for another BILLBOARD which, although 44780 compatible, requires more time to perform its operations, the program will not work until it is properly modified.

A more robust method of programming is to use the "Get BILLBOARD Status" command to determine whether the BILLBOARD is still busy executing the last instruction received.

The "Get BILLBOARD Status" command will return to us two tidbits of information; the information that is useful to us right now is found in DB7. In summary, when we issue the "Get BILLBOARD Status" command the BILLBOARD will immediately raise DB7 if it's still busy executing a command or lower DB7 to indicate that the BILLBOARD is no longer occupied. Thus our program can query the BILLBOARD until DB7 goes low, indicating the BILLBOARD is no longer busy. At that point we are free to continue and send the next command.

Since we will use this code every time we send an instruction to the BILLBOARD, it is useful to make it a subroutine. Let's write the code:

WAIT_BILLBOARD:CLR EN ;Start BILLBOARD commandCLR RS ;It's a commandSETB RW ;It's a read commandMOV DATA,#0FFh ;Set all pins to FF initiallySETB EN ;Clock out command to BILLBOARDMOV A,DATA ;Read the return valueJB ACC.7,WAIT_BILLBOARD ;If bit 7 high, BILLBOARD still busyCLR EN ;Finish the commandCLR RW ;Turn off RW for future commandsRET3.3.3 INITIALIZING THE BILLBOARDBefore you may really use the BILLBOARD, you must initialize and configure it. This is accomplished by sending a number of initialization instructions to the BILLBOARD.

The first instruction we send must tell the BILLBOARD whether we'll be communicating with it with an 8-bit or 4-bit data bus. We also select a 5x8 dot character font. These two options are selected by sending the command 38h to the BILLBOARD as a command. As you will recall from the last section, we mentioned that the RS line must be low if we are sending a command to the BILLBOARD. Thus, to send this 38h command to the BILLBOARD we must execute the following 8051 instructions:

CLR RSMOV DATA,#38hSETB ENCLR ENLCALL WAIT_BILLBOARDSo, in all, our initialization code is as follows:

INIT_BILLBOARD:

CLR RSMOV DATA,#38hSETB ENCLR ENLCALL WAIT_BILLBOARDCLR RSMOV DATA,#0EhSETB ENCLR ENLCALL WAIT_BILLBOARDCLR RSMOV DATA,#06hSETB ENCLR ENLCALL WAIT_BILLBOARDRETHaving executed this code the BILLBOARD will be fully initialized and ready for us to send display data to it.

3.3.4 CLEARING THE DISPLAY

When the BILLBOARD is first initialized, the screen should automatically be cleared by the 44780 controller. However, it's always a good idea to do things yourself so that you can be completely sure that the display is the way you want it. Thus, it's not a bad idea to clear the screen as the very first operation after the BILLBOARD has been initialized.

An BILLBOARD command exists to accomplish this function. Not surprisingly, it is the command 01h. Since clearing the screen is a function we very likely will wish to call more than once, it's a good idea to make it a subroutine:

CLEAR_BILLBOARD:

CLR RSMOV DATA,#01hSETB ENCLR ENLCALL WAIT_BILLBOARDRET

How that we've written a "Clear Screen" routine, we may clear the BILLBOARD at any time by simply executing an LCALL CLEAR_BILLBOARD. 3.3.5 WRITING TEXT TO THE BILLBOARDNow we get to the real meat of what we're trying to do: All this effort is really so we can display text on the BILLBOARD. Really, we're pretty much done.

Once again, writing text to the BILLBOARD is something we'll almost certainly want to do over and over--so let's make it a subroutine.

WRITE_TEXT:

SETB RSMOV DATA,ASETB ENCLR ENLCALL WAIT_BILLBOARDRET

The WRITE_TEXT routine that we just wrote will send the character in the accumulator to the BILLBOARD which will, in turn, display it. Thus to display text on the BILLBOARD all we need to do is load the accumulator with the byte to display and make a call to this routine.

A "HELLO WORLD" PROGRAM

Now that we have all the component subroutines written, writing the classic "Hello World" program--which displays the text "Hello World" on the BILLBOARD is a relatively trivial matter. Consider:

LCALL INIT_BILLBOARDLCALL CLEAR_BILLBOARDMOV A,#'H'LCALL WRITE_TEXTMOV A,#'E'LCALL WRITE_TEXTMOV A,#'L'LCALL WRITE_TEXTMOV A,#'L'LCALL WRITE_TEXTMOV A,#'O'LCALL WRITE_TEXTMOV A,#' 'LCALL WRITE_TEXTMOV A,#'W'LCALL WRITE_TEXTMOV A,#'O'LCALL WRITE_TEXTMOV A,#'R'LCALL WRITE_TEXTMOV A,#'L'LCALL WRITE_TEXTMOV A,#'D'LCALL WRITE_TEXT

The above "Hello World" program should, when executed, initialize the BILLBOARD, clear the BILLBOARD screen, and display "Hello World" in the upper left-hand corner of the display.

3.3.6 CURSOR POSITIONING

The above "Hello World" program is simplistic in the sense that it prints its text in the upper left-hand corner of the screen. However, what if we wanted to display the word "Hello" in the upper left-hand corner but wanted to display the word "World" on the second line at the tenth character? This sounds simple--and actually, it is simple. However, it requires a little more understanding of the design of the BILLBOARD.

The 44780 contains a certain amount of memory which is assigned to the display. All the text we write to the 44780 is stored in this memory, and the 44780 subsequently reads this memory to display the text on the BILLBOARD itself. This memory can be represented with the following "memory map":

In the above memory map, the area shaded in blue is the visible display. As you can see, it measures 16 characters per line by 2 lines. The numbers in each box is the memory address that corresponds to that screen position.

Thus, the first character in the upper left-hanad corner is at address 00h. The following character position (character #2 on the first line) is address 01h, etc. This continues until we reach the 16th character of the first line which is at address 0Fh.

However, the first character of line 2, as shown in the memory map, is at address 40h. This means if we write a character to the last position of the first line and then write a second character, the second character will not appear on the second line. That is because the second character will effectively be written to address 10h--but the second line begins at address 40h.

Thus we need to send a command to the BILLBOARD that tells it to position the cursor on the second line. The "Set Cursor Position" instruction is 80h. To this we must add the address of the location where we wish to position the cursor. In our example, we said we wanted to display "World" on the second line on the tenth character position. 3.2 ZIGBEE :3.2.1 Key Features:

Long Range Data Integrity:XBee Range

Indoor/Urban: up to 100 (30 m)

Outdoor line-of-sight: up to 300 (100 m)

Transmit Power: 1 mW (0 dBm)

Receiver Sensitivity: -92 dBm

XBee-PRO Range

Indoor/Urban: up to 300 (100 m)

Outdoor line-of-sight: up to 1 mile (1500 m)

Transmit Power: 100 mW (20 dBm) EIRP

Receiver Sensitivity: -100 dBm

RF Data Rate: 250,000

Advanced Networking & Security

Retries and Acknowledgements

DSSS (Direct Sequence Spread Spectrum)

Each direct sequence channels has over 65,000 unique network addresses available

Point-to-point, point-to-multipoint and peer-to-peer topologies supported

128-bit Encryption

3.2.2 SPECIFICATIONS:

3.2.3 PIN SIGNALS:

3.2.4 Electrical Characteristics:

Fig 5.k 3.2.5 FLOW CONTROL:

Fig 5.lDI (Data In) Buffer:

When serial data enters the RF module through the DI pin (pin 3), the data is stored in the DI Buffer until it can be processed.

Hardware Flow Control (CTS):

When the DI buffer is 17 bytes away from being full; by default, the module de-asserts CTS (high) to signal to the host device to stop sending data [refer to D7 (DIO7 Configuration) parameter]. CTS is re-asserted after the DI Buffer has 34 bytes of memory available.

How to eliminate the need for flow control:

1. Send messages that are smaller than the DI buffer size.

2. Interface at a lower baud rate [BD (Interface Data Rate) parameter] than the throughput data rate.Case in which the DI Buffer may become full and possibly overflow:If the module is receiving a continuous stream of RF data, any serial data that arrives on the DI pin is placed in the DI Buffer. The data in the DI buffer will be transmitted over-the-air when the module is no longer receiving RF data in the network.

DO (Data Out) Buffer:

When RF data is received, the data enters the DO buffer and is sent out the serial port to a host device. Once the DO Buffer reaches capacity, any additional incoming RF data is lost.

Hardware Flow Control (RTS):If RTS is enabled for flow control (D6 (DIO6 Configuration) Parameter = 1), data will not be sent out the DO Buffer as long as RTS (pin 16) is de-asserted.

Two cases in which the DO Buffer may become full and possibly overflow:

1. If the RF data rate is set higher than the interface data rate of the module, the module will receive data from the transmitting module faster than it can send the data to the host.

2. If the host does not allow the module to transmit data out from the DO buffer because of being held off by hardware or software flow control3.3 RS232 SERIAL CONNECTOR PIN ASSIGNMENT:The RS232 connector was originally developed to use 25 pins. In this DB25 connector pinout provisions were made for a secondary serial RS232 communication channel. In practice, only one serial communication channel with accompanying handshaking is present. Only very few computer have been manufactured where both serial RS232 channels are implemented. Also on a number of Telebit modem models the secondary channel is present. It can be used to query the modem status while the modem is on-line and busy communicating. On personal computers, the smaller DB9 version is more commonly used today. The diagrams show the signals common to both connector types in black. The defined pins only present on the larger connector are shown in red. Note, that the protective ground is assigned to a pin at the large connector where the connector outside is used for that purpose with the DB9 connector version. RS232 DB9 pinout

The pinout is also shown for the DEC modified modular jack. This type of connector has been used on systems built by Digital Equipment Corporation; in the early days one of the leaders in the mainframe world. Although this serial interface is differential (receive and transmit have their own floating ground level which is not the case with regular RS232) it is possible to connect RS232 compatible devices with this interface because the voltage levels of the bit streams are in the same range. Where the definition of RS232 focussed on the connection of DTE, data terminal equipment (computers, printers, etc.) with DCE, data communication equipment (modems), MMJ was primarily defined for the connection of two DTE's directly.

DescriptionSignal9-pin DTE25-pin DCESource DTE or DCE

Carrier DetectCD18from Modem

Receive DataRD23from Modem

Transmit DataTD32from Terminal/Computer

Data Terminal ReadyDTR420from Terminal/Computer

Signal GroundSG57from Modem

Data Set ReadyDSR66from Modem

Request to SendRTS74from Terminal/Computer

Clear to SendCTS85from Modem

Ring IndicatorRI922from Modem

4. DESCRIPTION OF DEVELOPMENT SYSTEM

4.1 CROSS COMPILERS

First of all we begin this chapter by giving a brief introduction about cross compilers in embedded programming and their applications. We know that the execution of code in a microcontroller takes place as a hexadecimal code. So we can program any microcontroller using an assembly language. Also though the use of cross compilers we can program the microcontrollers in any language like C or C++.

The cross compiler acts as a bridge between the programming software and microcontrollers. Suppose we are programming the microcontroller using C the code written in C language cannot be directly executed by microcontroller. So this code written in C is fed to a cross compiler which converts into hexadecimal code which is understood and executed by microcontroller. The advantages of using cross compilers is that in case of some applications programming the microcontroller using assembly language will become bulk and tedious. So when we use cross compilers we can program the microcontroller in any other language which is easy to program and debug also. The commonly used cross compilers are SDCC (Small devices C compiler), Keil etc.

In this our project the use of Keil cross compiler is to program the microcontroller. In this chapter we discuss the introduction to programming in Keil features of Keil and finally advantages of using Keil when compared to other cross compilers. When we are writing program for any microcontroller using cross compiler we cannot directly write the converted code on to the microcontroller. This means we need to use a special technique to load the program into the microcontroller. One of the methods is to use a microcontroller with a flash memory. Flash memory is similar to erasable programmable read only memory. So once program is written and debugged using cross compiler, we need to flash the program on to the flash memory of the memory. Once program is flashed the microcontroller is loaded with the hex code and it will be ready for execution.4.1.1 INTRODUCTION TO KEIL:

Keil software provides the premier 8051 development tools to industry .The keil software comprises of different tool kits. A tool kit consist of several application program that we can use to create our 8051 application .When we use keil software for our project the development cycle is some what similar to a software development project .It consist of creating source file in C or assembly language compiling or assembling the source files debugging error in the source file, linking file from complier and assembler and finally building a project linking all the files and testing the linked application.

4.1.2 FUNCTIONING OF KEIL

All the files are created through the micro vision integrated development environment are then passed to the C51 compiler or A51 assembler. The compiler and assembler process source files and create relocatable object files. Object files created by the compiler or assembler may be used by the library manager to create a library. A library is a specially formatted, ordered program collection of object modules that linker can process. When the linker processes a library, only the object modules in the library necessary for program creation are used. Object files created by the compiler and assembler and library files created by the library manager are processed by the linker to create an absolute object module. An absolute object file or module is an object file with no relocatable code. All the code in an absolute object file resides at fixed locations.

The absolute object file created by the linker may be used to program EPROM or other memory devices. The absolute object module may also be used with the dScope-51 debugger / simulator or with an in-circuit emulator. The dScope-51 source level debugger/simulator is ideally suited for fast, reliable high-level-language program debugging. The debugger contains a high-speed simulator and a target debugger that let you simulate an entire 8051 system including on-chip peripherals. By loading specific I/O drivers, we can simulate the attributes and peripherals of a variety of 8051 family. The RTX-51 real time operating system is a multitasking kernel for the 8051 family. The RTX-51 real time kernel simplifies the system design, programming, and debugging of complex applications where fast reaction to time critical event is essential. The kernel is fully integrated into the C51compiler and is easy to use. Task description tables and operating system consistency are automatically controlled by the BL51 code banking linker/locater.

4.1.3 DEVELOPMENT TOOLS IN KEIL

The Fig 4.1 shows the full extent of the Keil Software 8051 development tools. The tools listed in this diagram comprise the professional developers kit. In addition to the professional kit, Keil Software provides a number of other tool kits for the 8051 developer. The most capable kit is the professional developers kit is described as follows:

The professional developers kit includes everything the professional 8051 developer needs to create sophisticated embedded applications. This tool kit includes the following components:

C51 Optimizing C compiler,

A51 Macro Assembler,

BL51 Code Banking Linker/Locator,

OC51 Banked Object file converter,

OH51 Object-Hex converter,

LIB51 Library Manager,

dScope-1 Simulator/debugger,

tScope-51 Target Debugger,

Monitor-51 ROM Monitor and Terminal Program,

Integrated Development Environment,

RTX-51 Tiny Real-Time Operating System.

In addition, the professional developers kit includes the following tools for Windows users:

dScope-51 Simulator/Debugger for windows,

Micro Vision/51 Integrated Development Environment for windows.

The professional developers kit can be configured for all 8051 derivatives. The tools included in this kit can run any compatible computer.

4.1.4 C51 OPTIMIZING C CROSS COMPILER

The C programming language is a general-purpose programming language that provides code efficiency, elements of structured programming, and a rich set of operators. Its generality, combined with its absence of restrictions, make C a convenient and effective programming solution for a wide variety of software tasks. Many applications can be solved more easily and effectively with C than with other more specialized languages. The Keil software C51 optimizing cross compiler for the MS-DOS operating system is a complete implementation of the ANSI (American National Standards Institute) standard for the C language. The C51 compiler generates code for the 8051 microprocessor but is not a universal C compiler adapted for the 8051 target. It is a ground-up implementation dedicated to generating extremely fast and compact code for the 8051 microprocessor. For most 8051 applications, the C51 compiler gives software developers the flexibility of programming in /c while matching the code efficiency and speed of assembly language. Using a high-level language like C has many advantages over assembly language programming. For example:

Knowledge of the processor instruction set is not required. A rudimentary knowledge of the 8051s memory architecture is desirable but not necessary.

Register allocation and addressing mode details are managed by the compiler.

The ability to combine variable selection with specific operations improves program readability.

Keywords and operational functions that more nearly resemble the human thought process can be used.

Program development and debugging times are dramatically reduced when compared to assembly language programming.

The library files that are supplied provide many standard routines (such as formatted output, data conversions, and floating-point arithmetic) that may be incorporated into our application.

Existing routine can be reused in new programs by utilizing modular programming techniques available with C.

The C language is very portable and very popular. C compilers are available for almost all target systems. Existing software investments can be quickly and easily converted from or adapted to other processors or environments.

4.1.5 A51 MACRO ASSEMBLER

The A51 assembler is a macro assembler for the 8051 microcontroller family. It translates symbolic assembly language mnemonics into relocatable object code where the utmost speed, small code size, and hardware control are critical. The macro facility speeds development and conserves maintenance time since common sequences need only be developed once. The A51 assembler supports symbolic access to all features of the 8051 architecture and is configurable for the numerous 8051 derivatives. The A51 assembler translates an assembler source file into a relocatable object module. If the DEBUG control is used, the object file contains full symbolic information for debugging with dScope or an in-circuit emulator. In addition to the object file, the A51 assembler generates a list file which may optionally include symbol table and cross reference information. The A51 assembler is fully compatible with Intel ASM-51 source modules. The A51 assembler supports all members of the 8051 family. The special function register (SFR) set of the 8051 is predefined. However, the NOMOD51 control lets you override these definitions with processor-specific include files. The A51 assembler is shipped with include files for the 8051, 8051fx, 8051GB, 8052, 80152, 80451, 80452, 80515, 80C517, 80C517A, 8x552, 8xC592, 8xCL782, 8xCL410 and 80C320 microcontrollers. You can easily create include files for other 8051 family members.

4.1.6 BL51 CODE BANKING LINKER/LOCATOR

The 51 code banking linker/locator combines one or more object modules into a single executable 8051 program. The linker also resolves external and public references, and assigns absolute addresses to relocatable programs segments. The BL51 code banking linker/locator processes object modules created by the keil C51 compiler and A51 assembler and the Intel PL/M-51 compiler and ASM-51 assembler. The linker automatically selects the appropriate run-time library and links only the library modules that are required. Normally, you invoke the BL51 code banking linker/locator from the command line specifying the names of the object modules to combine. The default controls for the BL51 code banking linker/locator have been carefully chosen to accommodate most applications without the need to specify additional directives. However, it is easy for us to specify custom settings for your applications.

4.1.7 OC51 BANKED OBJECT FILE CONVERTER

The OC51 banked object file converter creates absolute object modules for each code bank in a banked object module. Banked object modules are created by the BL51 code banking linker/locator when you create a bank switching application. Symbolic debugging information is copied to the absolute object files and can be used by dScope or an in-circuit emulator. We may use the OC51 banked object file converter to create absolute object modules for the command area and for each code bank in your banked object module. You may then generate Intel HEX files for each of the absolute object modules using the OH51 object-hex converter.

4.1.8 OH51 OBJECT-HEX CONVETER

The OH51 object-hex converter creates Intel hex files from absolute object modules. Absolute object modules can be created by the BL51 code baking linker or by the OC51 banked object file converter. Intel hex files are ASCII files that contain a hexadecimal representation of your application. They can be easily loaded into a device programmer for writing on Erasable programmable read only memory.LIB51 LIBRARY MANAGER

The LIB51 library manager lets you create and maintain library files. A library file is a formatted collection of one or more object files. Library files provide a convenient method of combining and referencing a large number of object files. Libraries can be effectively used by the BL51 code banking linker/locator. The LIB51 library manager lets you create a library file, add object modules to a library file, remove object modules from may be controlled interactively or from the command line.

DSCOPE-51 for windows

DScope-51 is a source level debugger and simulator for programs created with the keil C51 compiler and A51 assembler and the Intel PL/M-51 compiler and ASM-51 assembler. DScope-51 is a software-only product that lets us simulate the features of an 8051 without actually having target hardware. We may have used Scope-51 to test and debug our embedded applications before actual 8051 hardware is ready. DScope-51 simulates a wide variety of 8051 peripherals including the internal serial port, external I/O, and timers.

4.1.9 VISION/51 FOR WINDOWS

Microvision/51 is an integrated software development platform that includes a full function editor, project manager, make facility, and environment control for the keil 8051 tools. When we use Vision/51 speeds our embedded applications development by providing the following:

Standard Windows user interface,

Dialog boxes for all environment and development tool settings,

Multiple file editing capability,

Full function editor with user-definable key sequences,

Application manager for adding external programs into the pull-down menu,

Project manager for creating and maintaining projects,

Integrated make facility for building target programs from your projects,

On-line help system.

5. APPLICATION SOFTWARE

5.1 APPLICATION SOFTWARE DISCRIPTION

Application software is a computer program that functions and is operated by means of a computer, with the purpose of supporting or improving the software user's work. In other words, it is the subclass of computer software that employs the capabilities of a computer directly and thoroughly to a task that the user wishes to perform. This should be contrasted with system software (infrastructure) or middleware (computer services/ processes integrators), which is involved in integrating a computer's various capabilities, but typically does not directly apply them in the performance of tasks that benefit the user. In this context the term application refers to both the application software and its implementation. In some types of embedded systems, the application software and the operating system software may be indistinguishable to the user, as in the case of software used to control a VCR, DVD player or microwave oven.

The application software for this project has been developed from a high level graphical programming language (visual basic).This method of implementation gives the user a more flexibility to have hands on the system. The application software is a virtual representation of the actual instrument and provides all facilities for the user to control the working of the system. This technique of operating the system (the actual instrument) is highly advantageous, as it does not permit the actual instrument to be misused, for example, here, the minimum and maximum ranges of the system is defined and hence prevents the user from exceeding the limits. Thus the application software provides high security to the actual instrument. Moreover certain graphical representation of the real time values with high resolution can also be implemented.

5.2 SCREEN SHOTS6. CONCLUSIONThe purpose of this report was to show a design of an electronic billboard can be effectively realized using BILLBOARD. The conclusion is split in two. The first part describes what design choices have been made, what the design looks like and how it performs. What is needed to implement the design using BILLBOARD is discussed in the second part.

As a receiver, a standard 2.4GHz device, found in many other applications, suffices. Other research showed that both the distance at which the data could be received and the transmission rates were acceptable. The controller that will be consists of three components. First a receiver/decoder is required. This buffers the serial data from the receiver device and forwards it to the storage management component in 8-bit packets. The central component, which acts as the main controller, stores the received data in the memory while at the same time sending data to the screen. The screen is driven by the last component of the controller, the screen controller. This drives the screen we have chosen.