EMBEDDED SYSTEM.docx

7/31/2019 EMBEDDED SYSTEM.docx

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EMBEDDED SYSTEM

What is Embedded System?

Embedded system employs a combination of software & hardware to perform a specific

function. It is a part of a larger system which may not be a computerWorks in areactive & time constrained environment.Any electronic system that uses a CPU chip, but that is not a general-purposeworkstation, desktop or laptop computer is known as embedded system. Such systemsgenerally use microprocessors; microcontroller or they may use custom-designed chipsor both. They are used in automobiles, planes, trains, space vehicles, machine tools,cameras, consumer and office appliances, cell phones, PDAs and other handhelds aswell as robots and toys. The uses are endless, and billions of microprocessors areshipped every year for a myriad of applications.

In embedded systems, the software is permanently set into a read-only memory such asa ROM or flash memory chip, in contrast to a general-purpose computer that loads itsprograms into RAM each time. Sometimes, single board and rack mounted general-purpose computers are called "embedded computers" if used to cont

Embedded System Applications :-

Consumer electronics, e.g., cameras, cell phones etc.

Consumer products, e.g. washers, microwave ovens etc.

Automobiles (anti-lock braking, engine control etc.)

Industrial process controller & defense applications.

Computer/Communication products, e.g. printers, FAX machines etc.

Medical Equipments.

ATMs

Aircrafts


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DIFFERENCE BETWEEN MICROPROCESSORS

AND MICROCONTROLLERS:

A Microprocessor is a general purpose digital computer central processing

unit(C.P.U) popularly known as CPU on the chip. The Microprocessorscontain no RAM, no ROM, and no I/P O/P ports on the chip itself.

On the other hand a Microcontroller has a C.P.U(microprocessor) in addition

to a fixed amount of RAM, ROM, I/O ports and a timer all on a single chip.

In order to make a Microprocessor functional we must add RAM, ROM, I/O

Ports and timers externally to them,i.e any amount of external memory can be

added to it.

But in controllers there is a fixed amount of memory which makes them ideal

for many applications.

The Microprocessors have many operational codes(opcodes) for moving data

from external memory to the C.P.U

Whereas Microcontrollers may have one or two operational codes.

DISADVANTAGES OF MICROPROCESSORS

OVER MICROCONTROLLERS

System designed using Microprocessors are bulky

They are expensive than Microcontrollers

We need to add some external devices such as PPI chip, Memory,

Timer/counter chip, Interrupt controller chip,etc. to make it functional.

Types of microcontroller architecture:


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There are two types of Microcontroller architecture designed for embedded systemdevelopment. These are:1)RISC- Reduced instruction set computer2)CISC- Complex instruction set computer

Difference between CISC and RISC:

CISC stands for Complex Instruction Set Computer. Most PC's use CPU based on thisarchitecture. For instance Intel and AMD CPU's are based on CISC architectures.Typically CISC chips have a large amount of different and complex instructions. Incommon CISC chips are relatively slow (compared to RISC chips) per instruction, but uselittle (less than RISC) instructions. MCS-51 family microcontrollers based on CISCarchitecture.

RICS stands for Reduced Instruction Set Computer. The philosophy behind it is that almost

no one uses complex assembly language instructions as used by CISC, and people mostlyuse compilers which never use complex instructions. Therefore fewer, simpler and fasterinstructions would be better, than the large, complex and slower CISC instructions.However, more instructions are needed to accomplish a task. Atmells AVRmicrocontroller based on RISC architecture.

History of 8051Intel Corporation introduced an 8-bit microcontroller called 8051 in 1981 this controllerhad 128 bytes of RAM, 4k bytes of on chip ROM, two timers, one serial port, and fourports all are on single chip. The 8051 is an 8 bit processor, meaning that the CPU can

work on only 8 bit data at a time. Data larger than 8 bits broken into 8 bit pieces to beprocessed by CPU. It has for I/O 8 bit wide.Features of the 8051:-

Feature QuantityROM 4K bytesRAM 128 bytesTimer 2I/O pins 32

Serial port 1Interrupt sources 6

8051 Architecture Overview


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The 8051 family is one of the most common microcontroller architectures used worldwide.

8051 based microcontrollers are offered in hundreds of variants from many different

silicon manufacturers

.The 8051 is based on an 8-bit CISC core with Harvard architecture. It's an 8-bit CPU,

optimized for control applications with extensive Boolean processing (single-bit logiccapabilities), 64K program and data memory address space and various on-chip

peripherals.

The 8051 microcontroller family offers developers a wide variety of high-integration and

cost-effective solutions for virtually every basic embedded control application. From traffic

control equipment to input devices and computer networking products, 8051 u.c deliver

high performance together with a choice of configurations and options matched to the

special needs of each application. Whether it's low power operation, higher frequency

performance, expanded on-chip RAM, or an application-specific requirement, there's a

version of the 8051 microcontroller that's right for the job.

When it's time to upgrade product features and functionality, the 8051 architecture puts

you on the first step of a smooth and cost-effective upgrade path - to the enhanced

performance of the 151 and 251 microcontrollers.


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Block diagram of 8051


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Internal Architecture of 8051


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Pin configuration of 8051


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There are four ports P0, P1, P2 and P3 each use 8 pins, making them 8-bit ports. All the

ports upon RESET are configured as output, ready to be used as output ports. To use any of

these ports as an input port, it must be programmed.

Port 0:- Port 0 occupies a total of 8 pins (pins 32-39) .It can be used for input or output. To

use the pins of port 0 as both input and output ports, each pin must be connected externally

to a 10K ohm pull-up resistor. This is due to the fact that P0 is an open drain, unlike P1,

P2, and P3.Open drain is a term used for MOS chips in the same way that open collectorisused for TTL chips. With external pull-up resistors connected upon reset, port 0 is

configured as an output port. For example, the following code will continuously send outto port 0 the alternating values 55H and AAH

Port 0 as input:- With resistors connected to port 0, in order to make it an input, the port

must be programmed by writing 1 to all the bits. In the following code, port 0 is configured

first as an input port by writing 1's to it, and then data is received from the port and sent to

P1.


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Dual Role of Port 0 :-Port 0 is also designated as AD0-AD7, allowing it

to be used for both address and data. When connecting an 8051/31 to an external memory,

port 0 provides both address and data. The 8051 multiplexes address and data through port

0 to save pins. ALE indicates if P0 has address or data. When ALE = 0, it provides data

D0-D7, but when ALE =1 it has address and data with the help of a 74LS373 latch.

Port 1:- Port 1 occupies a total of 8 pins (pins 1 through 8). It can be used as input or

output. In contrast to port 0, this port does not need any pull-up resistors since it already

has pull-up resistors internally. Upon reset, Port 1 is configured as an output port. For

example, the following code will continuously send out to port1 the alternating values 55h& AAh

Port 1 as input:-To make port1 an input port, it must be programmed as such by writing 1

to all its bits. In the following code port1 is configured first as an input port by writing 1s

to it, then data is received from the port and saved in R7 ,R6 & R5.

Port 2 :-Port 2 occupies a total of 8 pins (pins 21- 28). It can be used as input or

output. Just like P1, P2 does not need any pull-up resistors since it already has pull-up

resistors internally. Upon reset,Port 2 is configured as an output port. For example, the

following code will send out continuously to port 2 the alternating values 55h and AAH.

That is all the bits of port 2 toggle continuously.

Port 2 as input:- To make port 2 an input, it must programmed as such by writing 1 to all

its bits. In the following code, port 2 is configured first as an input port by writing 1s to it.Then data is received from that port and is sent to P1 continuously.


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Dual role of port 2:- In systems based on the 8751, 8951, and DS5000, P2 is used as

simple I/O. However, in 8031-based systems, port 2 must be used along with P0 to provide

the 16-bit address for the external memory. As shown in pin configuration 8051, port 2 is

also designed as A8-A15, indicating the dual function. Since an 8031 is capable of

accessing 64K bytes of external memory, it needs a path for the 16 bits of the address.While P0 provides the lower 8 bits via A0-A7, it is the job of P2 to provide bits A8-A15 of

the address. In other words, when 8031 is connected to external memory, P2 is used for the

upper 8 bits of the 16 bit address, and it cannot be used for I/O.

Port 3:- port 3 occupies a total of 8 pins, pins 10 through 17. It can be used as input oroutput. P3 does not need any pull-up resistors, the same as P1 and P2 did not. Although

port 3 is configured as an output port upon reset. Port 3 has the additional function ofproviding some extremely important signals such as interrupts. This information appliesboth 8051 and 8031 chips. There functions are as follows:-

P3.0 and P3.1 are used for the RxD and TxD serial communications signals. Bits P3.2

and P3.3 are set aside for external interrupts. Bits P3.4 and P3.5 are used for timers 0 and

1. Finally P3.6 and P3.7 are used to provide the WR and RD signals of external memories

connected in 8031 based systems.

PORT 3 Function pinP3.0 RxD 10P3.1 TxD 11P3.2 ___

Int0

12

P3.3 ___Int1

13

P3.4 T0 14P3.5 T1 15P3.6 ___

WR16

P3.7 ___RD

17


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ALE/PROG

Address Latch Enable is an output pulse for latching the low byte of the address duringaccesses to external memory. This pin is also the program pulse input (PROG) duringFlash programming. In normal operation, ALE is emitted at a constant rate of 1/ 6 theoscillator 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. Ifdesired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bitset, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin isweakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is inexternal execution mode.

PSENProgram Store Enable is the read strobe to external program memory. When theAT89S8252 is executing code from external program memory, PSEN is activated twice

each machinecycle, except that two PSEN activations are skipped during each access to external datamemory.

EA/VPPExternal Access Enable. EA must be strapped to GND in order to enable the device tofetch 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. EAshould be strapped to VCC for internal program executions. This pin also receives the 12-

volt programming enable voltage (VPP) during Flash programming when 12-voltprogramming is selected.

XTAL1Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2Output from the inverting oscillator amplifier.

AT89s8252AT89S8252 is an ATMEL controller with the core of intel MCS-51. It has same pinconfiguration as give above.The AT89S8252 is a low-power, high-performance CMOS 8-bit microcomputer with 8Kbytes of Downloadable Flash programmable and erasable read only memory and 2K bytesof EEPROM. The device is manufactured using Atmels high density nonvolatile memory

technology and is compatible with the industry standard 80C51 instruction set and pinout.The on-chip Downloadable Flash allows the program memory to be reprogrammed in-


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system through an SPI serial interface or by a conventional nonvolatile memoryprogrammer. By combining a versatile 8-bit CPU with Downloadable Flash on amonolithic chip, the Atmel AT89S8252 is a powerful microcomputer which provides ahighly flexible and cost effective solution to many embedded control applications. TheAT89S8252 provides the following standard features: 8K bytes of Downloadable Flash,2K bytes of EEPROM, 256 bytes of RAM, 32 I/O lines, programmable watchdog timer,

two Data Pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture,a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S8252is designed with static logic for operation down to zero frequency and supports twosoftware selectable power saving modes. The Idle Mode stops the CPU while allowing theRAM, timer/counters, serial port, and interrupt system to continue functioning. The PowerDown Mode saves the RAM contents but freezes the oscillator, disabling all other chipfunctions until the next interrupt or hardware reset.The Downloadable Flash can be changed a single byte at a time and is accessible throughthe SPI serial interface. Holding RESET active forces the SPI bus into a serialprogramming interface and allows the program memory to be written to or read from

unless Lock Bit 2 has been activated.

Features Compatible with MCS-51Products 8K bytes of In-System Reprogrammable Downloadable Flash Memory- SPI Serial Interface for Program Downloading- Endurance: 1,000 Write/Erase Cycles 2K bytes EEPROM

- Endurance: 100,000 Write/Erase Cycles 4.0V to 6V Operating Range Fully Static Operation: 0 Hz to 24 MHz Three-Level Program Memory Lock 256 x 8 bit Internal RAM 32 Programmable I/O Lines Three 16 bit Timer/Counters Nine Interrupt Sources Programmable UART Serial Channel SPI Serial Interface Low Power Idle and Power Down Modes Interrupt Recovery From Power Down Programmable Watchdog Timer Dual Data Pointer Power Off Flag


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Pin Description

Furthermore, P1.4, P1.5, P1.6, and P1.7 can be configured as the SPI slave port select, datainput/output and shift clock input/output pins as shown in the following table.

Port 1 also receives the low-order address bytes during Flash programming andverification.

Hardware interfacings and programming

There are two types of programming language used for microcontroller programming:1)Low Level Language(Assembly Language)2) High Level Language(C Language)_

ALE/PROG

Address Latch Enable is an output pulse for latching the low byte of the address duringaccesses to external memory. This pin is also the program pulse input (PROG) duringFlash programming. In normal operation, ALE is emitted at a constant rate of 1/ 6 theoscillator 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. Ifdesired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bitset, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin isweakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is inexternal execution mode.


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PSEN

Program Store Enable is the read strobe to external program memory. When theAT89S8252 is executing code from external program memory, PSEN is activated twiceeach machinecycle, except that two PSEN activations are skipped during each access to external data

memory.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device tofetch 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. EAshould be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming when 12-voltprogramming is selected.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2

Output from the inverting oscillator amplifier.

Hardware interfacings and programming

There are two types of programming language used for microcontroller programming:1)Low Level Language(Assembly Language)2) High Level Language(C Language)

Programming in assembly language:

TOOLS USED:1). 8051 assembler cum simulator.2).command prompt as a programming environment.

Introduction to programming in assembly language:


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assembly languages weredeveloped that provided mnemonics for the machine code instructions, plus others featuresthat made programming faster and less prone to error.The term mnemonic is frequentlyused in computer science and engg. literature to refer to codes and abbreviations that arerelatively easy to remember .Asssembly language programs must be translated intomachine code by a program called an ASSEMBLER.Assembly language is referred to as

a low-level-language .Now we look at 8051 assembly language format and use an 8051

Assembler to create a ready-to run program.

An assembly language instruction consists of four fields:-

[label:] mnemonic [operands] [;comment]

Brackets indicates that a field is optional,and not all lines have them.Bracket shouldnot be typed in.

1.The label field allows the program to refer to a line of code by name.the label field cannot exceed a certain no. of characters.

2.The assembly language mnemonics(instruction) and operands fields together perform thereal work of the program and accomplish the tasks for which the program was written.

3.The comment field begins with a ;. Comments may be at the and of a line or on a lineby themselvess .

8051 basic instructions:we describe the basic instructions of the 8051 andgive their formats with some examples.1).arithmetic instructions2).logical instructions3).jump,loop,call instructions

arithmetic instructions:the arithmetic instructions are used to perform arithmetic

operations like addition,subtraction ,multiplication, division etc.

1)ADD:- this instruction is used to add 2 operands.the 1 operand should be in accumulatorand 2 in the other register.

eg. MOV R0,#20MOV A,#10ADD A,R0MOV P1,A


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Here,# is used to load immediate value and we observe the final value on port 1.

2)MUL:-this instruction is used to multiply 2 operands. the 1 operand should be inaccumulator and 2 in the other register.

eg.MOV R0,#20MOV A,#10MUL ABMOV P1,A


3)DIV:- this instruction is used to divide 2 operands. the 1 operand should be inaccumulator and 2 in the other register.

eg.MOV R0,#20MOV A,#10DIV ABMOV P1,A


logical instructions: Apart from the input/output instructions ,logic instructions are someof the most widely used instructions.the logical instructions are used to perform logicaloperations likeAND,OR,EXOR etc.

1). MOV A,#35H ;A=35HANL A,#0FH ;A AND 0FH(now A=05)

According to this operation, the content 35H gets ANDing with 0FH.

2). MOV A,#04 ;A=04ORL A,#30H ;A=A OR 30H(now A=34H)

According to this operation, the content 35H gets ANDing with 0FH.

Jump,loop,call instructions:


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the Jump,loop,call instructions are used to perform logicaloperations in the sequence of instructions to be executed ,it is often necessary to transferprogram control to a different location.

We have used high level language for microcontroller programming due to its givenadvantages over assembly:

Advantages of C over Assembly language programming:

Knowledge of the processor instruction set is not required.

Details like register allocation and addressing of memory and data is managed by the

compiler.

Programs get a formal structure and can be divided into separate functions.

Programming and program test time is drastically reduced, this increases efficiency.

Keywords and operational functions can be used that come closer to how humans

think.

The supplied and supported C libraries contain many standard routines such as

numeric conversions.

Reusable code: Existing program parts can be more easily included into new

programs, because of the comfortable modular program construction techniques.

The C language based on the ANSI standard is very portable. Existing programs can

be quickly adapted to other processors as needed.

THE 8051 INTERRUPTS

There are two methods in which a micro-controller can provide its services to its internal

and external environment:

1) POLLING: Microcontroller checks the device continuously while using thismethod. But it results in wastage of machine cycles of the micro-controller.


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2) INTERRUPTS: Here every device tells the micro-controller when it needs theservices from microcontroller.

Actually, only 5 interrupts are available to the user in the 8051, but many manufacturersdata sheets state that there are 6 interrupts since they include reset. The 6 interrupts in the8051 are allocated as follows:

1).Reset: when the reset pin is activated, the 8051 jumps to address location 0000.this isthe power-up reset.

2).Two interrupts are set aside for the timers:

One for timer 0 and one for timer 1.memory locations 000BH and 001BH in the interruptvector table belong to timer0 and timer1, respectively.

3).Two interrupts are set aside for hardware external hardware interrupts. Pin numbers12(p3.2) and 13(p3.3) in port 3 are the external hardware interrupts INT0 and INT1,respectively. These external interrupts are also referred to as EX1 and EX2.

4).Serial communication has a single interrupts that belongs to both receive and transmit.

ELECTROMAGNETIC RELAYS

A relay is an electrically controllable switch widely used in industrial controls, automobilesand appliances. It allows the isolation of two separate sections of a system with twodifferent voltage sources. The electromechanical (or electromagnetic) relay (EMR) has 3components: the coil, spring and contacts. When current flows through the coil, a magnetic

field is created around the coil (the coil is energized) which causes the armature to beattracted to the coil. The armatures contact acts like a switch and closes or opens a circuit.When the coil is not energized, a spring pulls the armature to its normal state of open orclosed.

In choosing a relay, the following characteristics need to be considered:

1) The contacts can be normally open (NO) or normally closed (NC). Inthe NC type, the contacts are closed when the coil is not energized.In the NO, the contacts are open when the coil is un-energized.

2) There can be one or more contacts (SPST, SPDT, DPDT relays).3) The voltage and current needed to energize the coil. The voltage can

vary from a few volts to 50 volts, while the current can be from fewmA to 20mA. The relay has a minimum voltage below which the coilwill not be energized. This minimum voltage is called the pull-involtage.


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INTERFACING OF VARIOUS DEVICES

1) LED Interfacing

Hardware interfacing of LED with AT89s8252

Title

Size Document Number Rev

Date: Sheet of

Custom

1 1Tuesday, December 26, 2006

Q21

BC547A

Q14BC547A

D26

LED

VCC

R40

330E

D27

LED

VCC

R41

330E

VCC

D28

LED

R61

330E

D29

LED

R62

330E

VCC

Q15

BC547A

D22

LED

R37

330E

VCC

Q16

BC547A

Q17

BC547A

Q18

BC547A

D23

LED

VCC

R38

330E

Q19

BC547A D24

LED

VCC

R39

330E

D25

LED

R63

330E

VCC

Q20

BC547A

U10

AT89S8252

RST9

XTAL218 XTAL119

GND

20

PSEN29

ALE/PROG30

EA/VPP

31

VCC

40

P1.0/T21

P1.1/T2-EX2

P1.23

P1.34

P1.4/SS5

P1.5/MOSI6

P1.6/MISO7

P1.7/SCK8

P2.0/A821

P2.1/A922

P2.2/A1023

P2.3/A1124

P2.4/A1225

P2.5/A1326

P2.6/A1427

P2.7/A1528

P3.0/RXD10P3.1/TXD11

P3.2/INT012

P3.3/INT113

P3.4/T014

P3.5/T115

P3.6/WR16P3.7/RD17

P0.0/AD039

P0.1/AD138

P0.2/AD237

P0.3/AD336

P0.4/AD435

P0.5/AD534

P0.6/AD633

P0.7/AD732

C4533pF

C4633pF

Y8

8 Mhz

12

3

4

VCCVCC

R710K

C4710uF/16V

VCC

C48104


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C code for Blinking LEDs connected on PORT2:

#includevoid delay(unsigned int i);

void main(void){

While(1){P2=0x00;Delay(0xffff);P2=0x00;Delay(0xff);}}void delay(unsigned int i)

{while(i!=0){i--;}}

C code for running LED connected on PORT2:

#includevoid delay(unsigned int i);void main (){P0=0x00;while (1){delay(0xffff);P2_0=1;delay(0xffff);P2_0=0;P2_1=1;delay(0xffff);P2_1=0;P2_2=1;delay(0xffff);


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P2_2=0;P2_3=1;delay(0xffff);P2_3=0;P2_4=1;delay(0xffff);

P2_4=0;P2_5=1;delay(0xffff);P2_5=0;P2_6=1;delay(0xffff);P2_6=0;P2_7=1;delay(0xffff);P2_7=0;

P2_0=1

}}

void delay(unsigned int i){while (i!=0){

i--;}}

2) Hardware interfacing of LCD(JHD162A):

On most displays, the pins are numbered on the LCDs printed circuit board, but if not, it is

quit easy to locate pin1. Since the pin is connected to ground, it often has a thicker PCB

track connected to it, and it is generally connected to the metal work at some point.


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The function of each of the connections is shown in the table below:-

Pins 1 & 2 are the power supply lines, Vss & Vdd. The Vdd pin should be connected to the

positive supply & Vss to the 0V supply or ground.

Although the LCD module data sheets specify 5V D.C. supply (at only a few milliamps),

supplies of 6V & 4.5V both work well, and even 3V is sufficient for some modules.

Consequently, these modules can be effectively and economically powered by batteries.

Pin 3 is a control pin, Vee, which is used to alter the contrast of the display. Ideally, these pin

should be connected to a variable voltage supply. A preset potentiometer connected betweenthe power supply lines, with its wiper connected to the contrast pin is suitable in many cases,

but be aware that some modules may require a

negative potential; as low as 7V in some cases. For absolute simplicity, connecting this pin to

0V will often suffice.

Pin 4 is register select (RS) line.

PIN NO. NAME FUNCTION

1 Vss Ground

2 Vdd +ve supply


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3 Vee contrast

4 RS Register select

5 R/W Read/Write

6 E Enable

7 D0 Data Bit 08 D1 Data Bit 1

9 D2 Data Bit 2

10 D3 Data Bit 3

11 D4 Data Bit 4

12 D5 Data Bit 5

13 D6 Data Bit 6

14 D7 Data Bit 7

Three command control inputs. When this line is low, data bytes transferred to thedisplay are treated as commands, and data bytes read from the display indicate itsstatus. By setting the RS line high, character data can be transferred to and from themodule.

Pin 5 is (R/W) line. This line is pulled low in order to write commands or character datato the module, or pulled high to read character data or status information from itsregisters.

Pin 6 is Enable (E) line. This input is used to initiate the actual transfer of commands orcharacter data between the module and the data lines. When writing to the display, datais transferred only on the high to low transition of this signal. However, when readingfrom the display, data will become available shortly after the low to high transition andremain available until the signal falls low again.

Pins 7 to 14 are the eight data bus lines (D0 to D7). Data can be transferred to and fromthe display, either as a single 8-bit byte or as two 4-bit nibbles. In the latter case, onlythe upper four data lines (D4 to D7) are used. This $-bit mode is beneficial when usinga microcontroller, as fewer I/O lines are required.


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C code for LCD display

#include #define LCDPRT P1#define RS P3_3

#define EN P3_4void delay(unsigned int i);void lcd_cmd(unsigned char a);void display(unsigned char b);void wait(void);void Init_lcd(void);void cursor_position(unsigned char c);

void main(void){

U1

AT89S52

RST9

XTAL218 XTAL119

GND

20

PSEN29

ALE/PROG30

EA/VPP

31

VCC

40

P1.0/T21

P1.1/T2-EX2

P1.23

P1.34

P1.4/SS5

P1.5/MOSI6

P1.6/MISO7

P1.7/SCK8

P2.0/A8 21

P2.1/A922

P2.2/A1023

P2.3/A1124

P2.4/A1225

P2.5/A1326

P2.6/A1427

P2.7/A1528

P3.0/RXD10

P3.1/TXD11

P3.2/INT012

P3.3/INT113

P3.4/T014

P3.5/T115

P3.6/WR16P3.7/RD17

P0.0/AD039 P0.1/AD138 P0.2/AD237 P0.3/AD336 P0.4/AD435 P0.5/AD534 P0.6/AD633 P0.7/AD732

J2 LCD

1 2 3 4 5 6 7 8 910

11

12

13

14

15

16

C133pF

C233pF

Y1

12

3

4

R110K

C310uF 16V

VCC

VCC R52

56E

VCC

VCC

RS

Hardware intetrfacing of LCD with AT89s52 microcontroler

EN


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init_lcd();while(1)

{cursor_position(0x01);display('N');

cursor_position(0x02);display('E');cursor_position(0x03);display('T');cursor_position(0x04);display('M');cursor_position(0x05);display('A');cursor_position(0x06);display('X');

}

}

void delay (unsigned int i){while (i!=0){

i--;}

}

void lcd_cmd(unsigned char a){wait();LCDPRT=a;RS=0;EN=1;EN=0;}void display(unsigned char b){

wait ();LCDPRT=b;RS=1;


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EN=1;EN=0;}void wait(void){unsigned int count=300;

while(count!=0){count--;}

}

void Init_lcd(void){

lcd_cmd(0x3c);lcd_cmd(0x0c);lcd_cmd(0x06);lcd_cmd(0x01);

}void clear_lcd(void){lcd_cmd(0x01);

}void cursor_position(unsigned char c){lcd_cmd(c+0x80);}

C code for string display on LCD:

#include#define LCDPRT P1#define RS P3_3#define EN P3_4code unsigned char name_arry[]={"NETMAX$"};void display_string(unsigned char *sp);void lcd_cmd(unsigned char a);void display(unsigned char b);void wait(void);


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void Init_lcd(void);void cursor_position(unsigned char c);

void main(void){Init_lcd();

cursor_position(0x40);display_string(&name_arry);

}

void display_string(unsigned char *sp)

{while(*sp!='$')

{

display(*sp);

sp=sp+1;}

}

void lcd_cmd(unsigned char a){wait ();LCDPRT=a;RS=0;EN=1;EN=0;}void display(unsigned char b){wait ();LCDPRT=b;RS=1;EN=1;EN=0;}void wait(void){


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unsigned int count=300;while(count!=0){count--;}

}

void Init_lcd(void){lcd_cmd(0x3c);lcd_cmd(0x0c);lcd_cmd(0x06);

lcd_cmd(0x01);}void cursor_position(unsigned char c){lcd_cmd(c+0x80);

}

3) ADC-0804 interfacing with AT89s52:

The ADC0804 family is CMOS 8-Bit, successive-approximation A/D converters

which use a modified potentiometer ladder and are designed to operate with the

8080A control bus via three-state outputs. These converters appear to theprocessor as memory locations or I/O ports, and hence no interfacing logic is

required. The differential analog voltage input has good common mode- rejection

and permits offsetting the analog zero-input voltage value. In addition, the voltage

reference input can be adjusted to allow encoding any smaller analog voltage span

to the full 8 bits of resolution.

Features

80C48 and 80C80/85 Bus Compatible - No Interfacing Logic Required

Conversion Time < 100 s

Easy Interface to Most Microprocessors


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Differential Analog Voltage Inputs

TTL Compatible Inputs and Outputs

On-Chip Clock Generator

0V to 5V Analog Voltage Input Range (Single + 5V Supply)

No Zero-Adjust Required

PIN DIAGRAM


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Hardware interfacing of ADC-0804 for Temperature monitoring

When interfacing is being done then gets lowered then only it allows the

controller to read the data, otherwise controller can not read the data.

is always grounded.

is software controlled.

C- code For temperature monitoring system

#include #define LCDPRT P1#define RS P3_3#define EN P3_4#define SOC P3_2#define EOC P3_5

R2

10K

C610uF 16V

VCC

C13104

EOC

SOC

VCC

C141uf/16v

R6

220E

U4ADC0804

+IN6

-IN7

AGND

8

VREF/29

GND

10

DB711DB6

12 DB513 DB414 DB315 DB216 DB117 DB018

CLKR19

VCC/VREF

20

CLKIN4

INTR5

CS1

RD2

WR3

VCC

R510K

R17

10K

C7

150pF

U21TL431

2

3

1

C81uf/16v

C9CAP

RSEN

LCD

CON16_0

1 2 3 4 5 6 7 8 910

11

12

13

14

15

16

VCCRS EN R55

56E

Temprature monitoring system

U22 LM35/SO

GND3

VCC1

2

OUTPUT

R53

1k

VCC

U2

AT89S8252

RST9

XTAL218 XTAL119

GND

20

PSEN29 ALE/PROG30

EA/V

PP

31

V

CC

40

P1.0/T21

P1.1/T2-EX2

P1.23

P1.34

P1.4/SS5

P1.5/MOSI6

P1.6/MISO7

P1.7/SCK8

P2.0/A821

P2.1/A922

P2.2/A1023

P2.3/A1124

P2.4/A1225

P2.5/A1326

P2.6/A1427

P2.7/A15 28

P3.0/RXD10

P3.1/TXD11

P3.2/INT0 12

P3.3/INT113

P3.4/T014

P3.5/T115

P3.6/WR16

P3.7/RD17

P0.0/AD039 P0.1/AD138 P0.2/AD237 P0.3/AD336 P0.4/AD435 P0.5/AD534 P0.6/AD633 P0.7/AD732

C433pF

C533pF

Y2

CRYSTAL

12

3

4

VCCVCC


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unsigned char read_adc(void);void delay(unsigned int i);void lcd_cmd(unsigned char a);void display(unsigned char b);void wait(void);void Init_lcd(void);

void clear_lcd(void);void cursor_position(unsigned char c);

void disp_dec(unsigned int digit);code unsigned char table[16]={'0','1','2','3','4','5','6','7','8','9'};

void main(void){unsigned char e;P2=0xff;Init_lcd();

while(1){cursor_position(0x00);e=read_adc();disp_dec(e);}

}unsigned char read_adc(void){

unsigned char n;SOC=0;SOC=1;while(EOC==1){

n=P2;}

return n;}

void delay (unsigned int i){while (i!=0){i--;}

}void lcd_cmd(unsigned char a)


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{wait();LCDPRT=a;RS=0;EN=1;EN=0;

}void display(unsigned char b){

wait ();LCDPRT=b;RS=1;EN=1;EN=0;}void wait(void)

{unsigned int count=300;while(count!=0){count--;}

}

void Init_lcd(void)

{lcd_cmd(0x3c);lcd_cmd(0x0c);lcd_cmd(0x06);lcd_cmd(0x01);}

void cursor_position(unsigned char c){lcd_cmd(c+0x80);}

void disp_dec(unsigned int digit){unsigned int temp;


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if(digit99 && digit


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C- code for serial transmission(from Microcontroller to PC)

#includevoid Init_SPT(void);void transmit_serial(unsigned char a);

void delay(unsigned int i);void main(void){Init_SPT();while(1){delay(0XFFFF);transmit_serial('N');delay(0XFFFF);

transmit_serial('E');

delay(0XFFFF);transmit_serial('T');delay(0XFFFF);

transmit_serial('M');delay(0XFFFF);

transmit_serial('A');delay(0XFFFF);

transmit_serial('X');delay(0XFFFF);

}

}void Init_SPT(void){

TMOD=0x20;

TH1=0xfd;

TR1=1;

SCON=0x40;

}


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void transmit_serial(unsigned char a){SBUF=a;delay(500);TI=0;

}void delay(unsigned int i){while(i!=0){i--;

}}

b)Serial Reception(From PC to microcontroller)

J3 LCD

1 2 3 4 5 6 7 8 910

11

12

13

14

15

16

VCC

NETMAX

R54

56E

VCC

RS EN

RSEN

SPT TXD

SPT RXD

U11

AT89S8252

RST9

XTAL218 XTAL119

GND

20

PSEN29

ALE/PROG30

EA/VPP

31

VCC

40

P1.0/T21

P1.1/T2-EX2

P1.23

P1.34

P1.4/SS5

P1.5/MOSI6

P1.6/MISO7

P1.7/SCK8

P2.0/A821

P2.1/A922

P2.2/A1023

P2.3/A1124

P2.4/A1225

P2.5/A1326

P2.6/A1427

P2.7/A1528

P3.0/RXD10P3.1/TXD11

P3.2/INT012

P3.3/INT113

P3.4/T014

P3.5/T115

P3.6/WR 16P3.7/RD

17

P0.0/AD039 P0.1/AD138

P0.2/AD237 P0.3/AD336 P0.4/AD435 P0.5/AD534 P0.6/AD633 P0.7/AD732

C3433pF

C3533pF

Y9

CRYSTAL

12

3

4

VCCVCC

R810K

C4910uF 16V

VCC

C50104

C5110UF/16V

VCC

C5210UF/16V

VCC

C5310UF/16V

C54104

C55 10UF/16V

U12

MAX232

C1+1

C1-3

C2+4

C2-5

VCC

16

GND

15

V+2

V-6

R1OUT12

R2OUT9

T1IN11

T2IN10

R1IN13

R2IN8

T1OUT14

T2OUT7

J8

SERIAL PORT OF PC

123


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C- code for serial reception:#include #define LCDPRT P1#define RS P3_3#define EN P3_4

void Init_SPT(void);unsigned char receive_serial(void);

void delay(unsigned int i);void lcd_cmd(unsigned char a);void display(unsigned char b);void wait(void);void Init_lcd(void);void clear_lcd(void);void cursor_position(unsigned char d);

void disp_hex(unsigned char digit);void disp_dec(unsigned int digit);code unsigned char lkup_tbl01[16]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

void main(void){

unsigned char e;

Init_lcd();Init_SPT();

while(1){

e=receive_serial();cursor_position(0x00);display(e);

}

}

void Init_SPT(void){


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PCON=PCON&0x7F;

TMOD=TMOD&0x0F;

TMOD=TMOD|0x20;

TH1=0xfd;

SCON=0X50;

TR1=1;

}

void delay (unsigned int i){

while (i!=0){i--;}

}void lcd_cmd(unsigned char a){wait();LCDPRT=a;

RS=0;EN=1;EN=0;}void display(unsigned char b){wait ();LCDPRT=b;RS=1;EN=1;EN=0;}void wait(void){unsigned int count=300;while(count!=0){count--;


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}

}

void Init_lcd(void){

lcd_cmd(0x3c);lcd_cmd(0x0C);lcd_cmd(0x06);lcd_cmd(0x14);lcd_cmd(0x1C);lcd_cmd(0x01);

}void cursor_position(unsigned char d){

lcd_cmd(d+0x80);}

Interfacing of seven segment display

VCC

R19 220E

R20 220E

R21 220E

cR24 220E

VCC

R25 220E

U16

AT89S8252

RST9

XTAL218 XTAL119

GND

20

PSEN29 ALE/PROG

30

EA/VPP

31

VCC

40

P1.0/T21

P1.1/T2-EX2

P1.23

P1.34

P1.4/SS5

P1.5/MOSI6

P1.6/MISO7

P1.7/SCK8

P2.0/A821

P2.1/A922

P2.2/A1023

P2.3/A1124

P2.4/A1225

P2.5/A1326

P2.6/A14

27

P2.7/A15 28

P3.0/RXD10P3.1/TXD11P3.2/INT012P3.3/INT113P3.4/T014P3.5/T115P3.6/WR16P3.7/RD17

P0.0/AD039

P0.1/AD138

P0.2/AD237

P0.3/AD336

P0.4/AD435

P0.5/AD534

P0.6/AD633

P0.7/AD732

Y3

8 Mhz

12

3

4

VCCVCC

R34 220E

R3510KSIP

1

23456789

R3610K

C4810uF/16V

VCC

P01P02P03P04P05P06P07

VCC

P08

VCC

d

C49104

VCCVCC

VCC

R37

10k SIP

1

2345678

e

C42

33PF

C4333PF

U374LS47

D07 D11 D22 D36

BI/RBO4

RBI5

LT3

A13B12

C11

D10

E9

F15

G14

VCC

16

GND

8

U12

74LS47

D07 D11 D22 D36

BI/RBO

4

RBI5

LT3

A

13B12

C11D10E9

F 15

G14

V

CC

16

GND

8

c

VCC

U13

DIP20

d

2

e

1

d

7

G/V

3

c

4

dot

5

e

6

G/V

8

dot

9

c

1

0

b

11

a

12

G/v

13

g

15

b

16

a

17

G/V

18

f

19

g

20

f

14

VCC

d

R13 220E

VCC

R3 220E

R7 220E

R11

10k SIP

1

2345678

R14 220E

R 8 220E

e

R 9 220ER15 220E

R16 220E

VCC


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C code for seven segment display

#include#define EOC P3_6#define SOC P3_7

void delay(unsigned int i);unsigned char read_adc(void);void dec(unsigned int digit) ;void main (void){unsigned char a=0;P0=0x08;while(1){delay(0xffff);

a=read_adc();dec(a);

a++;delay(0xffff);dec(a);P0=1;

delay(0xffff);

P0=2;delay(0xffff);

P0=3;delay(0xffff);

P0=4;delay(0xffff);

}}

void delay(unsigned int i){while(i!=0){i--;}


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}unsigned char read_adc(void)

{unsigned char n=0;SOC=0;SOC=1;

while(EOC==1){n=P2;

}return n;

}

void dec(unsigned int x){

x=(x/10)*6+x;P0=x;

}

void bcdconv(unsigned int mb)

{

unsigned char x;unsigned char y;x=mb&0x0f;x=x|0x30;y=mb&0xf0;y=y>>4;y=y|0x30;display(y);display(x);}


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C-code for handling of INT0 interrupt:

#include

void delay(unsigned int i)

{

while(i!=0)

i--;

}

void int0(void) interrupt 0

{

if(INT0==0)

{

while(1)

{

P0=0xF0;

delay(0xFFFF);

P0=0x0F;

delay(0xFFFF);

}}}

void main(){

EA=1;

EX0=1;

While(1)

{

P0=0xFF;

delay(0xFFFF);

P0=0x00;

delay(0xFFFF);

}}


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