Path Tracing System for an Autonomous Robot

8/10/2019 Path Tracing System for an Autonomous Robot

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PATH TRACING SYSTEM FOR AN

AUTONOMOUS ROBOT

INTRODUCTION

The purpose of the project is to design a path tracing system for

a robot which is not under human control. The robot is designed

to move around at its own will. The movements of the robot

might depend on various factors which include information from

the sensors, some task specified by the user by programming the

microcontroller which specifies the movements based on the

task to be accomplished.

The path tracing system will track the movements of the robot

and makes a map from the starting point to the stopping point of

the robot. The path tracing system will help in supervising the

movements of the robot and, if required, in controlling the robot

to reach the destination. However, to trace the path to scale and

with accuracy, a lot of measuring devices need to be interfaced

with the microcontroller. Some of these devices are speedometer

(which will help in determining the speed of the robot), a device

to measure the r.p.m. of the motors and a device to measure the

angle of steering. Interfacing these devices with themicrocontroller will enhance the accuracy of the path tracing

system as more information is available regarding the

movements.


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REQUIREMENTS OF THE PROJECT

The project is based on both hardware and software. The

hardware section consists of the robot, two microcontrollers,

transmitter and receiver (RF-434 MHz), development boards

and DB9 connector to enable serial port communication through

USB. One of the microcontrollers is mounted on the robot and

the other microcontroller is connected to the computer for serial

port communication using DB9 connector (used to convert USB

port to a serial port). The RF-434 transmitter is connected to the

microcontroller of the robot and the data relevant to tracing the

path is sent to the RF-434 receiver connected to the computer.

The data received by the microcontroller is then sent to the

computer using serial port communication.

The software portion comes to play while programming the

microcontrollers and while processing the received data. The

programs for the microcontrollers are in Embedded C. The

AVR-GCC cross compiler converts the C- program into hex

code. MATLAB has been used to receive data from the serial

device. A program in MATLAB creates a map of the path

traversed by the robot by using the received data. The MATLAB

program also returns the final position of the robot (in terms of

the row and column of the matrix used to create the map) withrespect to the initial position which is, by default, the centre of

the matrix.


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HARDWARE COMPONENTS

1.

Robot (using D.C. motors)

2.

Two ATMega32 Microcontrollers

3.

Wireless Transmitter Section

4.

Wireless Receiver Section

5.

DB9 Connector

6.

RS-232 Cable

HARDWARE DETAILS

1.

Robot: The robot used for the project has two D.C. motors driven

using L293D (motor driver IC). The data to the motor driver is

provided by the microcontroller.

Figure 1: ROBOT


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2.

ATMega32 Microcontroller and Programmer:

1 MicrocontrollerThe Mini Board is designed for AVR Atmega32.

LCD PORT BUZZER MCU POWER LED LDR

USB PORT RESET ISP PWM LED DC JACK


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2 Power Supply

The supply voltage to the AVR microcontroller is provided eitherthrough DC Jack or USB. It is connected to the AVR's VCC pin.

2.1 DC Jack

Connect external power supply to this jack.

2.2 USB

Connect USB connector to this Port.

2.3 Power LED

LED will glow when Power in On.

3 Reset Button

Press this button to reset the Mini Board.

Reset Button is connected on Pin no. 9 (RESET)

4 LDR

LDR (Light Dependent Resistor) isconnected to microcontroller forapplications that are dependent onintensity of external light source.

LDR is connected on Pin no. PA1


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5 ISP

In-System Programming uses the AVR internal SPI (Serial PeripheralInterface) to download code into the flash and EEPROM memory of

the AVR. ISP programming requires only VCC, GND, RESET and 3signal lines for programming.

The AVR can be programmed at the normal operatingvoltage, normally 2.7V-6.0V. No high voltage signalsare required. The ISP programmer can program boththe internal flash and EEPROM. It also programs fuse

bits for selecting clock options, startup time and

internal Brown Out Detector (BOD) for the device.

During ISP programming the 6-wire cable must always be connected tothe header marked ISP (6PIN).

ISP port also acts power source. ISP is connected on Pin nos.

MOSI MISO SCK RESET VCC GND

PB5 PB6 PB7 RESET (9) VCC GND

6 PWM LED

PWM LED is connected to microcontroller forapplications that require PWM application. LED isused to check proper functioning of PWMapplication. PWM LED is connected on Pin no

PD5


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7 PORT A, B, C & DThese Ports are connected to microcontroller for interfacing I/O Pins ofMicrocontroller.

PORT APORT BPin B0 (PB0) - Pin B3 (PB3)

Pin B0 (PB3) - Pin B3 (PB7)

PORT C

PORT D

3.Wireless Transmitter Section : Thewireless transmitter section

consists of an RF-434 MHz transmitter along with the HT-12E

encoder which performs the dual function of providing an address

to the transmitter as well as converting parallel input data into the

serial output data. The transmitter section is mounted on the robot.

Figure : Transmitter Section


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4.

Wireless Receiver Section : The wireless receiver section

consists of an RF-434 MHz receiver along with the HT-12D

decoder which performs the function of analyzing the address of

the data sender and converting the serial input data into paralleloutput data. The receiver section is connected to the

microcontroller communicating with the computer.

Figure : Receiver Section

DB9 Connector : The DB9(originallyDE-9) connector is an analog 9-pin plug of the D-Subminiature connector family (D-Sub or Sub-D). The

DB9 connector is mainly used for serial connections, allowing for the

asynchronous transmission of data as provided for by standard RS-232

(RS-232C).


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Figure : DB9 Connector

Pins

Pin number Name

1 CD - Carrier Detect

2 RXD - Receive Data

3 TXD - Transmit Data

4 DTR - Data Terminal Ready

5 GND - Signal Ground

6 DSR - Data Set Ready

7 RTS - Request To Send

8 CTS - Clear To Send

9 RI - Ring Indicator

Shield


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3.USART Control and Status Register C (UCSRC)

4.USART Baud Rate Register

5.USART I/O Data Register

Basics of Serial Port Programming in MATLAB

The MATLAB serial port interface provides direct access to peripheral

devices such as modems, printers, and scientific instruments that you

connect to your computer's serial port. This interface is established

through a serial port object. The serial port object supports functions and

properties that allow us to

Configure serial port communications

Use serial port control pins

Write and read data

Use events and callbacks


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Record information to disk

Supported Serial Port Interface Standards:

Over the years, several serial port interface standards have beendeveloped. These standards include RS-232, RS-422, and RS-485 - all of

which are supported by the MATLAB serial port object. Of these, the

most widely used interface standard for connecting computers toperipheral devices is RS-232.

The original serial port interface standard was given by RS-232, which

stands for Recommended Standard number 232. The termRS-232is still

in popular use, and is used in this guide when referring to a serial

communication port that follows the TIA/EIA-232 standard. RS-232defines these serial port characteristics:

The maximum bit transfer rate and cable length

The names, electrical characteristics, and functions of signals

The mechanical connections and pin assignments

Primary communication is accomplished using three pins: the Transmit

Data pin, the Receive Data pin, and the Ground pin. Other pins are

available for data flow control, but are not required.

Connecting Two Devices with a Serial Cable

The RS-232 standard defines the two devices connected with a serial

cable as the Data Terminal Equipment (DTE) and Data Circuit-

Terminating Equipment (DCE). This terminology reflects the RS-232

origin as a standard for communication between a computer terminal

and a modem.

Throughout this guide, your computer is considered a DTE, while

peripheral devices such as modems and printers are considered DCEs.Many scientific instruments function as DTEs.


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Because RS-232 mainly involves connecting a DTE to a DCE, the pin

assignments are defined such that straight-through cabling is used,

where pin 1 is connected to pin 1, pin 2 is connected to pin 2, and so on.

The following diagram shows a DTE to DCE serial connection using the

transmit data (TD) pin and the receive data (RD) pin.

If you connect two DTEs or two DCEs using a straight serial cable, the

TD pins on each device are connected to each other, and the RD pins on

each device are connected to each other. Therefore, to connect two like

devices, you must use a null modemcable. As shown in the following

diagram, null modem cables cross the transmitting and receiving lines in

the cable.

Serial Port Signals and Pin Assignments

Serial ports consist of two signal types: data signals and control signals.

To support these signal types, as well as the signal ground, the RS-232

standard defines a 25-pin connection. However, most Windows and


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UNIX platforms use a 9-pin connection. In fact, only three pins are

required for serial port communications: one for receiving data, one for

transmitting data, and one for the signal ground.

The following diagram shows the pin assignment scheme for a 9-pinmale connector on a DTE.

The pins and signals associated with the 9-pin connector are described in

the following table. Refer to the RS-232 standard for a description of the

signals and pin assignments used for a 25-pin connector.

Serial Port Pin and Signal Assignments

Pin Label Signal Name Signal Type

1 CD Carrier Detect Control

2 RD Received Data Data

3 TD Transmitted Data Data

4 DTR Data Terminal Ready Control

5 GND Signal Ground Ground

6 DSR Data Set Ready Control

7 RTS Request to Send Control

8 CTS Clear to Send Control

9 RI Ring Indicator Control

The Data Pins

Most serial port devices support full-duplex communication meaning

that they can send and receive data at the same time. Therefore, separate


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pins are used for transmitting and receiving data. For these devices, the

TD, RD, and GND pins are used. However, some types of serial port

devices support only one-way or half-duplexcommunications. For these

devices, only the TD and GND pins are used. This guide assumes that a

full-duplex serial port is connected to your device.

The TD pin carries data transmitted by a DTE to a DCE. The RD pin

carries data that is received by a DTE from a DCE.

The Control Pins

The control pins of a 9-pin serial port are used to determine the presence

of connected devices and control the flow of data. The control pins

include

The RTS and CTS Pins

The DTR and DSR Pins

The CD and RI Pins

The RTS and CTS Pins. The RTS and CTS pins are used to signal

whether the devices are ready to send or receive data. This type of data

flow controlcalled hardware handshakingis used to prevent data

loss during transmission. When enabled for both the DTE and DCE,hardware handshaking using RTS and CTS follows these steps:

1.The DTE asserts the RTS pin to instruct the DCE that it is ready to

receive data.

2.

The DCE asserts the CTS pin indicating that it is clear to send data

over the TD pin. If data can no longer be sent, the CTS pin is

unasserted.

3.

The data is transmitted to the DTE over the TD pin. If data can nolonger be accepted, the RTS pin is unasserted by the DTE and thedata transmission is stopped.


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The DTR and DSR Pins. Many devices use the DSR and DTR pins to

signal if they are connected and powered. Signaling the presence of

connected devices using DTR and DSR follows these steps:

1.

The DTE asserts the DTR pin to request that the DCE connect tothe communication line.

2.The DCE asserts the DSR pin to indicate it is connected.

3.DCE unasserts the DSR pin when it is disconnected from thecommunication line.

The DTR and DSR pins were originally designed to provide an

alternative method of hardware handshaking. However, the RTS and

CTS pins are usually used in this way, and not the DSR and DTR pins.

Refer to your device documentation to determine its specific pinbehavior.

The CD and RI Pins. The CD and RI pins are typically used to

indicate the presence of certain signals during modem-modem

connections.

A modem uses a CD pin to signal that it has made a connection with

another modem, or has detected a carrier tone. CD is asserted when theDCE is receiving a signal of a suitable frequency. CD is unasserted if the

DCE is not receiving a suitable signal.

The RI pin is used to indicate the presence of an audible ringing signal.

RI is asserted when the DCE is receiving a ringing signal. RI is

unasserted when the DCE is not receiving a ringing signal (e.g., it is

between rings).

Serial Data Format

The serial data format includes one start bit, between five and eight data

bits, and one stop bit. A parity bit and an additional stop bit might be

included in the format as well. The following diagram illustrates theserial data format.


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The following notation expresses the format for serial port data:

number of data bits - parity type - number of stop bits

For example, 8-N-1 is interpreted as eight data bits, no parity bit, and

one stop bit, while 7-E-2 is interpreted as seven data bits, even parity,and two stop bits.

The data bits are often referred to as a character because these bitsusually represent an ASCII character. The remaining bits are called

framing bitsbecause they frame the data bits.

The Serial Port Session

This example describes the steps you use to perform any serial port task

from beginning to end.

The serial port session comprises all the steps you are likely to take

when communicating with a device connected to a serial port. These

steps are:

1.Create a serial port object Create a serial port object for a

specific serial port using theserialcreation function.

Configure properties during object creation if necessary. In

particular, you might want to configure properties associated with

serial port communications such as the baud rate, the number of

data bits, and so on.


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2.Connect to the device Connect the serial port object to thedevice using thefopenfunction.

After the object is connected, alter the necessary device settings by

configuring property values, read data, and write data.

3.Configure properties To establish the desired serial port object

behavior, assign values to properties using the set function or dotnotation.

In practice, you can configure many of the properties at any time

including during, or just after, object creation. Conversely,

depending on your device settings and the requirements of your

serial port application, you might be able to accept the defaultproperty values and skip this step.

4.Write and read dataWrite data to the device using the fprintfor

fwritefunction, and read data from the device using thefgetl,fgets,

fread,fscanf,orreadasyncfunction.

The serial port object behaves according to the previously

configured or default property values.

5.

Disconnect and clean up When you no longer need the serial

port object, disconnect it from the device using thefclosefunction,

remove it from memory using the delete function, and remove itfrom the MATLAB workspace using theclearcommand.

Displaying Property Names and Property Values

After we create the serial port object, use the set function to display allthe configurable properties to the command line. Additionally, if a

property has a finite set of string values, set also displays these values.

s = serial('COM1');

set(s)


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ByteOrder: [ {littleEndian} | bigEndian ]

BytesAvailableFcn

BytesAvailableFcnCount

BytesAvailableFcnMode: [ {terminator} | byte ]

ErrorFcnInputBufferSize

Name

OutputBufferSize

OutputEmptyFcn

RecordDetail: [ {compact} | verbose ]

RecordMode: [ {overwrite} | append | index ]

RecordName

TagTimeout

TimerFcn

TimerPeriod

UserData

SERIAL specific properties:BaudRate

BreakInterruptFcn

DataBits

DataTerminalReady: [ {on} | off ]

FlowControl: [ {none} | hardware | software ]

Parity: [ {none} | odd | even | mark | space ]

PinStatusFcn

Port

ReadAsyncMode: [ {continuous} | manual ]

RequestToSend: [ {on} | off ]StopBits

Terminator


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Use the get function to display one or more properties and their current

values to the command line. To display all properties and their current

values:

get(s)ByteOrder = littleEndian

BytesAvailable = 0

BytesAvailableFcn =

BytesAvailableFcnCount = 48

BytesAvailableFcnMode = terminator

BytesToOutput = 0

ErrorFcn =

InputBufferSize = 512Name = Serial-COM1

OutputBufferSize = 512

OutputEmptyFcn =

RecordDetail = compact

RecordMode = overwrite

RecordName = record.txt

RecordStatus = off

Status = closed

Tag =

Timeout = 10

TimerFcn =

TimerPeriod = 1

TransferStatus = idle

Type = serial

UserData = []

ValuesReceived = 0

ValuesSent = 0

SERIAL specific properties:

BaudRate = 9600

BreakInterruptFcn =

DataBits = 8


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DataTerminalReady = on

FlowControl = none

Parity = none

PinStatus = [1x1 struct]

PinStatusFcn =Port = COM1

ReadAsyncMode = continuous

RequestToSend = on

StopBits = 1

Terminator = LF

To display the current value for one property, supply the property name

to get.

get(s,'OutputBufferSize')

ans =

512

To display the current values for multiple properties, include the

property names as elements of a cell array.

get(s,{'Parity','TransferStatus'})

ans =

'none' 'idle'

Configuring Property Values

We can configure property values using the set function:

set(s,'BaudRate',4800);

or the dot notation:

s.BaudRate = 4800;


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To configure values for multiple properties, supply multiple property

name/property value pairs to set.

set(s,'DataBits',7,'Name','Test1-serial')

In practice, we can configure many of the properties at any time whilethe serial port object exists including during object creation.

However, some properties are not configurable while the object is

connected to the device or when recording information to disk. For

information about when a property is configurable, see Property

Reference.

Reading data :

The Input Buffer and Data Flowdescribes the flow of data from

the device to MATLAB software.

Reading Text Data describes how to read from the device, and

format the data as text.

Reading Binary Data describes how to read binary (numerical)

data from the device.

The following table shows the functions associated with reading data.

Functions Associated with Reading Data

Function

Name

Description

fgetl Read one line of text from the device and discard the

terminatorfgets Read one line of text from the device and include the

terminator

fread Read binary data from the device

fscanf Read data from the device and format as text


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Function

Name

Description

readasync Read data asynchronously from the device

stopasync Stop asynchronous read and write operations

The following table shows the properties associated with reading data.

Properties Associated with Reading Data

Property Name Description

BytesAvailable Number of bytes available in the input buffer

InputBufferSize Size of the input buffer in bytes

ReadAsyncMode Specify whether an asynchronous read operation is

continuous or manual

Timeout Waiting time to complete a read or write operation

TransferStatus Indicate if an asynchronous read or write operation is

in progress

ValuesReceived

Total number of values read from the device


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PROGRAMS :

1.Sample program for the microcontroller connected to the

robot: This program is written in Embedded C. The

microcontroller generates 4-bit values to control the D.C. motors.

1001 -> Forward movement

0101 -> Left turn

1010 -> Right turn

0110 -> Reverse gear

The microcontroller also sends the data about the movement of the

robot through the wireless transmitter section.

#define F_CPU 4000000UL

#include

#include

int main(void)

{

unsigned int count=1;

DDRC=0xFF;

DDRD=0xFF;

PORTC=0x09;

PORTD=0x01;

while(1)

{


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if(count%4==1)

{

PORTC=0x09;

PORTD=0x01;

}

else if(count%4==2)

{

PORTC=0x05;

PORTD=0x02;

_delay_ms(255);

PORTC=0x09;

}

else if(count%4==3)

{PORTC=0x0A;

PORTD=0x03;

_delay_ms(255);

PORTC=0x09;

}

else if(count%4==0)

{

PORTC=0x06;

PORTD=0x04;


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}

_delay_ms(255);

_delay_ms(255);

_delay_ms(255);

_delay_ms(255);

if(count==160)

count=1;

else

count++;

}

}

2.

Sample program for the microcontroller connected to the

computer: This program involves receiving the data from the

wireless receiver section and forwarding the interpreted data to the

computer via USART. The USART is first initialized by setting

the baud rate and the frame format. Then the data is sent

continuously to the computer.

#define F_CPU 4000000UL

#include

void USART_init(unsigned int b)

{

UBRRH=(unsigned char)(b>>8);

UBRRL=(unsigned char)b;


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UCSRA=(1


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{

count2=0;

count3=0;

count4=0;

if(count1==0)

{

data=0x09;

count1++;

}

else if (count1==1)

{

data=0x19;

}

USART_Transmit(data);}

else if((PINA & 0x0F)==0x02)

{

count1=0;

count3=0;

count4=0;

if(count2==0)

{

data=0x05;


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count2++;

}

else if (count2==1)

{

data=0x15;

}

USART_Transmit(data);

}


{

count1=0;

count2=0;

count4=0;

if(count3==0){

data=0x0A;

count3++;

}

else if (count3==1)

{

data=0x1A;

}



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}


{

count1=0;

count2=0;

count3=0;

if(count4==0)

{

data=0x06;

count4++;

}

else if (count4==1)

{

data=0x16;}


}

}

}

3.

Sample program for generating a map of the path traversed

by the robot on MATLAB: This sample program records a

particular number of moves, in this case a, and, finally, produces


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a map of all the moves. The program gets its input data from a

serial port device (COM8)connected to the computer. However,

before executing the program it should be made sure that the frame

format of the data sent by the microcontroller should match theframe format which is expected by the receiver.

Program:

functionh=testmapserial(a)

m=ones(8*a);

s=serial('COM8');

set(s,'FlowControl','hardware','StopBits',2);

i=4*a+1;j=4*a+1;

prev=1;

fopen(s);

forp=1:1:a

out=fread(s,1,'uint8');

if(out==9)

x=1;

elseif(out==5)x=2;

elseif(out==10)

x=3;

elseif(out==6)

x=4;

end

if(x==1)

if(prev==1)

fory=1:1:4

m(i-y,j)=0;

end

i=i-4;

elseif(prev==2)

fory=1:1:4


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m(i,j+y)=0;

end

j=j+4;

elseif(prev==3)

fory=1:1:4m(i,j-y)=0;

end

j=j-4;

elseif(prev==4)

fory=1:1:4

m(i+y,j)=0;

end

i=i+4;end

elseif(x==2)

if(prev==3)

fory=1:1:4

m(i-y,j)=0;

end

i=i-4;

prev=1;

elseif(prev==1)

fory=1:1:4

m(i,j+y)=0;

end

j=j+4;

prev=2;

elseif(prev==4)

fory=1:1:4

m(i,j-y)=0;end

j=j-4;

prev=3;

elseif(prev==2)

fory=1:1:4


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m(i+y,j)=0;

end

i=i+4;

prev=4;

endelseif(x==3)

if(prev==2)

fory=1:1:4

m(i-y,j)=0;

end

i=i-4;

prev=1;

elseif(prev==4)fory=1:1:4

m(i,j+y)=0;

end

j=j+4;

prev=2;

elseif(prev==1)

fory=1:1:4

m(i,j-y)=0;

end

j=j-4;

prev=3;

elseif(prev==3)

fory=1:1:4

m(i+y,j)=0;

end

i=i+4;

prev=4;end

elseif(x==4)

if(prev==4)

fory=1:1:4

m(i-y,j)=0;


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end

i=i-4;

elseif(prev==3)

fory=1:1:4

m(i,j+y)=0;end

j=j+4;

elseif(prev==2)

fory=1:1:4

m(i,j-y)=0;

end

j=j-4;

elseif(prev==1)fory=1:1:4

m(i+y,j)=0;

end

i=i+4;

end

end

h=imshow(m)

end

i

j

fclose(s);

delete(s);

clear s;

end

Documents

Path Tracing System for an Autonomous Robot