INTRODUCTORY CONCEPTSOBJECTIVE:

•What is Embedded System?

•Microprocessor Vs Microcontroller

•Embedded product Development cycle

•Embedded tools Overview

OBJECTIVE (Contd...)

• How Embedded System communicate to external world?

• Serial communication basics

WHAT IS EMBEDDED SYSTEMS?

GENERAL DEFINITION

Electronic equipment with

* In built intelligence

* Uses Dedicated Software

* Often no “real” keyboard

* Often limited display

But, Every system is unique….

TECHNICAL DEFINITIONElectronic equipment with Embedded chips in built

or

Micro Computer based System with intelligence embedded in built through program

GENERIC MICROCOMPUTERARCHITECTURE

INPUT UNIT

MEMORY UNIT

ALU

CONTROLUNIT

OUTPUTUNIT

CPU

CPU in a Single Chip

WHAT IS MICROPROCESSOR?

WHAT IS MICROCONTROLLER?

= Single Chip Micro Computer

Embedded Product Development Life Cycle

UnderstandUser Requirements

Analyze the requirements choose right Embedded chips

Choose ProgrammingLanguageHLL/ ASS

DevelopingAlgorithm

to solveproblem

PCB LayoutDesign

AB

Debugging

Testing UsingSimulator

CD

A

Coding, EditingCompiling/Assembling

Down LoadingProgram

PCB LayoutProcurement

Assemble Component

Test Hardware

B

E

Test S/Won HardwareUsing ICE

Finished Embedded

System

CD E

O.K

NOT O.KNOT O.K

Embedded Tools

•Cross Assembler / Compiler Linker • Debugger• Simulator• In Circuit Emulator

DSCOPE SIMULATOR

In Circuit Emulator

In Circuit Emulator (Contd..)

Input/Output Ports

Parallel Serial

How Embedded System Communicate to external World?

•Via Input/Output ports

EmbeddedSystem

1 byte at a time

PARALLEL INPUT/OUTPUT PORTS

Example for Parallel Communication

Parallel Input/Output

Advantage and disadvantage of parallel communication

Advantages Disadvantages* Data transfer rate is high.

* More number of wires, not suitable for larger distance communication

NOTE: Most of Embedded system has both

* parallel- used between on board peripherals* serial- used for larger distance communication

SERIAL COMMUNICATION

* Signal will be carried one bit at a time

Transmitter Receiver

Example for serial communication

Parameters to be considered for Serial Communication

• Synchronization

• Direction of DATA flow

• Framing

• Data speed

• Error checking

• Transmission medium

• Protocol

Synchronisation

Format Synchronous Asynchronous

Data Format Group ofCharacter

One characterat a time

Speed High(64Kb/s orhigher)

Less than 64Kb/s

Implementation Hardware Hardware(or ) Software

• Synchronous

• Asynchronous

• Simplex• Half duplex• Full duplex

Simplex: * Data flow only in one direction

e.g. T.V broadcasting, PC to printer

Data Direction

Half duplex:Two way communication, but data flow

only in one direction at a time.E.g. Walkie-Talkie

Full duplex:Two way communication simultaneously.

E.g.Telephone

Framing

• Start bit(s)

• Data bit(s)

• Parity bit(s)

• Stop bit(s)

STARTDATA PARITY

STOP

Error Checking

Sources of error:-

• Noise induced in Transmission media

• Differences in Ground levels, etc….

Techniques of Check Errors

1. Parity Checking2. Checksum (or) Longitudinal Redundancy check

(LRC)3.Cyclical Redundancy Check(CRC)

example:-

If baud rate of modem is 2400, then 2400 bits are transmitted per second.

Data Speed

Unit: Baud

How we will define Baud rate?

The number of bits per second

Transmission Medium

• Telephone Line

• Co-Axial cable

• Twisted Pair cable

• Fiber Optics

Example :- Modbus -Modicon

Data High way Plus -Allen Bradley

HART -Rosemount

TCP/IP

PROTOCOL

The rules that governs the transmission of data between two system.

EIA RS 232 C Standards

What is the Abbreviation of EIA?

Electronic Industry AssociationElectronic Industry Association

What is the RS in RS232 stands for?

Recommended StandardRecommended Standard

Electrical - Common Voltage and Signal Levels

Mechanical - Common Pin Wiring Configuration

Functional - A Minimal amount of Control

information between the Host and peripheral

Systems

What this standard specifies?What this standard specifies?

Electrical Signal Specification

• -3V to -15V is defined as logic ‘1’

• +3V to +15V is defined as Logic ‘0’

Mechanical SpecificationRS-232 specifies a 25-pin connector.

The connector for DCE is Male for the connector housing and Female for the connection pins.

The connector for DTE is a FemaleFemale housing with male male connection pins.

Most of the applications (including modems) use only a 9-pin connector with the minimum required signals as shown in the figure next.

TDRD

RTSCTS

DSRCOMMON

DCDDTR

RI

2345

6

7

8

2022

23

5

6

7

8

2022

4

DTE DCE

A Typical RS232 Connection

DTEPC

EmbeddedSystem

TXD TXD

RXD RXD

RS232Minimum Connection Required

Null Modem Connection

Disadvantages of RS232

• Maximum Distance is only 50 feet

• Maximum Speed 115Kbps

• Multiple Device connectivity not supported

• More number of wires

• Non-Standard Voltage levels

RS 485 Serial Communication Standard

This standard specifies only Electrical specification

• Only two wires are needed

• Operates in Differential mode

• The potential difference between two conductorcan be maximum of 2.5v

RS 485 Standard (Contd..)

• supports 32 Devices

• operates at 5v

• Maximum Speed is 10 Mbps

• Twisted pair cable is commonly used

1 2 32

R R

• Twisted pair cable is commonly used

PHYSICAL PHYSICAL

DATA LINK

NETWORK

TRANSPORT

SESSION

DATA LINK

NETWORK

TRANSPORT

SESSION

HOST A HOST B

PRESENTATION

APPLICATION

PRESENTATION

APPLICATION

OSI REFERENCE MODEL- 7 Layer Architecture

Physical Layer

Defines

• Electrical

• Mechanical characteristics of I/F to medium

• Data rate

• Modulation Demodulation techniques

Data Link Layer

Defines

• Medium Access Control

• Structures transmission

• Error checking and error -correction

Network Layer

• Routing of Message across different Networks

Defines

Defines

Transport Layer

• Ensures one host end to remote host communication

• Acknowledgement of message

• Retransmitting message

Session Layer

Defines

• Start and stop of communication

Presentation Layer

• Translates Application Message Format suitable to communicate system

Defines

Application Layer

• It is part of Application protocol

Defines

MODBUS PROTOCOL

• Follows Master- Slave Comm Architecture

• Only one device(i.e Master) can initiate transaction called QUERY

• The addressed device(i.e Slave) will respondto the Master's QUERY

• Two Modes of operationASCIIRTU

ASCII Mode(American Standard Code for Information Interchange)

Coding:

• Hexadecimal 0…….9,A…..F• Each Hexadecimal Character is represented in •equivalent ASCII

Bits/Byte:

1 Start Bit7 Data Bits1 bit for Odd/Even parity, no bit for no parity1 Stop bit,if parity is used, 2 bits if no parity is used

Modbus

M 984M 984 M 984M 984 M 984

M 984

PC-VuePC-VuePC-Vue

PC / GEM

PC-Vue

BM 85

DecantationMilk storage

Evaporator # 1

Mod

bus

Milk skimmingCIP

Pasteurizing

MaturingCream preparation

Butter making

Ferments preparationScraper

ChurningButter packing

CIP

Evaporator # 2By-products dry concentration

Maintenance

Control / MonitoringCream preparation Room

Control / MonitoringChurning RoomButter packing

Control / MonitoringBy-products manufacturing

Control / MonitoringMilk preparation Room

Butter By-productsCream preparationMilk preparation

A Typical a Network

Error Checking

Longitudinal Redundancy Check(LRC)

Example:

To transmit 38h Hexadecimal character,follows ODDparity

Start 0 0 0 1 1 1 0 0 Stop =ASCII 8h

Start 1 1 0 0 1 1 0 1 Stop =ASCII 3h

Message Frame - ASCII

QUERY

Start AddressFuncti

onData

LRCCheck

END

1CHAR

• •

2 CHAR

2 CHAR

#CHAR

2 CHAR 1

CHARCRLF

Start AddressFuncti

onByte

CountData

LRCCheck

END

1CHAR

2 CHAR

2 CHAR

#CHAR

#CHAR

2 CHAR

RESPONSE

1CHAR

RTU MODE

Coding:

• 8 bit binary, contains Hexadecimal number system 0….9,A……F

Bits/Byte:

1 Start Bit8 Data Bits1 bit for Odd/Even parity, no bit for no parity1 Stop bit, if parity is used,2 bits if no parity is used

Error Checking:Cyclical Redundancy Check(CRC)

Example:

To transmit 38 h Hexadecimal character,followsNo parity

Start 0 0 0 1 1 1 0 0 Stop 38h

QUERY

Start AddressFuncti

onData

CRCCheck

END

T1-T2-T3-T4 8BITS

8BITS

#8

BITS

16BITS

T1-T2-T3-T4

Message Frame - RTU

Start AddressFuncti

onByte

CountData

CRCCheck

END

T1-T2-T3-T4 8BITS

8BITS

#8

BITS

16BITS

T1-T2-T3-T4#8

BITS

RESPONSE