wireless controlled robotic car

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Wirelessly Robotic Car Control

System using Touch Screen

Habib Ullah

M Raza ShahM ASIF

ASIF FEROZ


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Approval CertificateThis is to certify that the Thesis submitted by Mr. HabibUllah, and Mr.

Raza Shah is of sufficient standard to justify its acceptance by the Department

of Electrical Engineering, University of Engineering and Technology, UET

Peshawar Pakistan.


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Abstract


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AcknowledgementWe would like to express our deep and sincere gratitude to our honorable teacher and project

supervisor, Engr. Sahibzada Fahim whose guidance and encouragement enabled us to

complete our project and thesis.

We would also like to thank our parents for their support and encouragement throughout

our educational careers. We would also like to thank our all respected teachers for helping us

throughout our Engineering Career.


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TABLE OF CONTENTSTITLE PAGE

APPROVAL SHEET ... i

LIST OF ABBREVIATIONS . iiABSTRACT iii

ACKNOWLEDGEMENTS v

TABLE OF CONTENTS .... vi

LIST OF FIGURES . ix

Chapter 1: Introduction 1

1.1. Robotic System ...... .................. 3

1.2. Touch Screens ....................... 3

1.2. Wireless Links........................ 3

1.2. BasicOperation ......................... 3

Chapter 2: Nuts and Bolts 1

1.1. Sainsmart 3.2 TFT Display ..... .................. 3

1.2. 27 MHZ transmitter ....................... 3

1.2. PIC MCUs ........................ 3

1.2. MPLABX ......................... 3

1.2. Roboic Toy Car ......................... 31.2. Embedded Tool ......................... 3

Chapter 3: Implementation 1

1.1. Touch Display Operation ..... .................. 3

1.2. Touch Screen Reading ....................... 3

1.2. Commands Transmission ........................ 3

1.2. Robot Moment ......................... 3

1.2. Code ......................... 3

Chapter 4: Application 1

1.1. App. In Mining Engg...... .................. 3

1.2. Security System ....................... 3

1.2.National Geographics ........................ 3

1.2. Robot Moment ......................... 3


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CHAPATER-1

Introduction

ROBOTIC SYSTEMrobot, any automatically operatedmachinethat replaces human effort,

though it may not resemble human beings in appearance or perform

functions in a humanlike manner. By extension,roboticsis the engineering

discipline dealing with the design, construction, and operation of robots.

The word robotcomes from the Slavic word robota, which means labor. The

play begins in a factory that makes artificial people called robots, creatures

who can be mistaken for humans

The word robotics first appeared inIsaac Asimovs science-fiction story

Runaround (1942). Along with Asimovs later robot stories, it set a new

standard of plausibility about the likely difficulty of developing intelligent

robots and the technical and social problems that might result. Runaround

also contained Asimovs famous Three Laws of Robotics:

1. A robot may not injure a human being, or, through inaction, allow a

human being to come to harm.

2. A robot must obey the orders given it by human beings exceptwhere such orders would conflict with the First Law.

3. A robot must protect its own existence as long as such protection

does not conflict with the First or Second Law.

Robotics is the branch oftechnologythat deals with the design,construction, operation, and application ofrobots,

[1]as well as computer

systems for their control, sensory feedback, and information processing.These technologies deal with automated machines that can take the

place of humans in dangerous environments or manufacturingprocesses, or resemble humans in appearance, behavior, and/or
http://www.britannica.com/EBchecked/topic/354611/machinehttp://www.britannica.com/EBchecked/topic/354611/machinehttp://www.britannica.com/EBchecked/topic/354611/machinehttp://www.britannica.com/EBchecked/topic/1384950/roboticshttp://www.britannica.com/EBchecked/topic/1384950/roboticshttp://www.britannica.com/EBchecked/topic/1384950/roboticshttp://www.britannica.com/EBchecked/topic/38699/Isaac-Asimovhttp://www.britannica.com/EBchecked/topic/38699/Isaac-Asimovhttp://www.britannica.com/EBchecked/topic/38699/Isaac-Asimovhttp://en.wikipedia.org/wiki/Technologyhttp://en.wikipedia.org/wiki/Technologyhttp://en.wikipedia.org/wiki/Technologyhttp://en.wikipedia.org/wiki/Robothttp://en.wikipedia.org/wiki/Robothttp://en.wikipedia.org/wiki/Robotics#cite_note-OED-1http://en.wikipedia.org/wiki/Robotics#cite_note-OED-1http://en.wikipedia.org/wiki/Robotics#cite_note-OED-1http://en.wikipedia.org/wiki/Robotics#cite_note-OED-1http://en.wikipedia.org/wiki/Robothttp://en.wikipedia.org/wiki/Technologyhttp://www.britannica.com/EBchecked/topic/38699/Isaac-Asimovhttp://www.britannica.com/EBchecked/topic/1384950/roboticshttp://www.britannica.com/EBchecked/topic/354611/machine


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cognition. Many of today's robots are inspired by nature contributing tothe field ofbio-inspired robotics.

The concept of creating machines that can operate autonomously datesback toclassical times, but research into the functionality and potential

uses of robots did not grow substantially until the 20thcentury.[2]Throughout history, robotics has been often seen to mimichuman behavior, and often manage tasks in a similar fashion. Today,robotics is a rapidly growing field, as technological advances continue,research, design, and building new robots serve various practicalpurposes, whetherdomestically,commercially, ormilitarily. Many robotsdo jobs that are hazardous to people such as defusing bombs, exploringshipwrecks, and mines.
http://en.wikipedia.org/wiki/Bio-inspired_roboticshttp://en.wikipedia.org/wiki/Bio-inspired_roboticshttp://en.wikipedia.org/wiki/Bio-inspired_roboticshttp://en.wikipedia.org/wiki/Classical_timeshttp://en.wikipedia.org/wiki/Classical_timeshttp://en.wikipedia.org/wiki/Classical_timeshttp://en.wikipedia.org/wiki/Robotics#cite_note-2http://en.wikipedia.org/wiki/Robotics#cite_note-2http://en.wikipedia.org/wiki/Robotics#cite_note-2http://en.wikipedia.org/wiki/Domestic_robothttp://en.wikipedia.org/wiki/Domestic_robothttp://en.wikipedia.org/wiki/Domestic_robothttp://en.wikipedia.org/wiki/Industrial_robothttp://en.wikipedia.org/wiki/Industrial_robothttp://en.wikipedia.org/wiki/Industrial_robothttp://en.wikipedia.org/wiki/Military_robothttp://en.wikipedia.org/wiki/Military_robothttp://en.wikipedia.org/wiki/Military_robothttp://en.wikipedia.org/wiki/Military_robothttp://en.wikipedia.org/wiki/Industrial_robothttp://en.wikipedia.org/wiki/Domestic_robothttp://en.wikipedia.org/wiki/Robotics#cite_note-2http://en.wikipedia.org/wiki/Classical_timeshttp://en.wikipedia.org/wiki/Bio-inspired_robotics


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Touch Screen

A touchscreen is an electronic visual display that can detect the

presence and location of a touch within the display area. The

term generally refers to touching the display of the device with a

finger or hand. Touch screens can also sense other passive

objects, such as a stylus. In other words, a touchscreen is any

monitor, based either on LCD (Liquid Crystal Display) or CRT

(Cathode Ray Tube) technology that accepts direct onscreen

input. The ability for direct onscreen input is facilitated by an

external (light pen) or an internal device (touch overlay and

controller) that relays the X, Y coordinates to the computer.

The touchscreen has two main attributes. First, it enables one to

interact directly with what is displayed, rather than indirectly

with a cursor controlled by a mouse or touchpad. Secondly, it lets

one do so without requiring any intermediate device that would

need to be held in the hand

Touchscreen technology has the potential to replace most

functions of the mouse and keyboard. The touchscreen interface

is being used in a wide variety of applications to improve human -computer interaction. As the

technology advances, people may be

able to operate computers without mice and keyboards. Becauseof its convenience, touch screen technology solutions has been

applied more and more to industries, applications, products and

services, such as Kiosks, POS (Point-of-Sale), consumer

electronics, tablet PC, moderate to harsh Machine Control,

Process Control, System Control/Office Automation and Car PC,

etc.

TYPES OF TOUCHSCREEN TECHNOLOGYThe touch panels themselves are based around four basic screen

technologies: Resistive, Capacitive, Surface Acoustical Wave

(SAW) and Infrared (IR). Each of those designs has dis tinctadvantages and disadvantages. The detailed study of each is as

follows:

ResistiveResistive LCD touchscreen monitors rely on touch overlay, which

is composed of a flexible top layer and a rigid bottom layer

separated by insulating dots, attached to a touchscreen controller.

The inside surface of each of the two layers is coated with a

transparent metal oxide coating of Indium Tin Oxide (ITO) that

facilitates a gradient across each layer when voltage is applied.

Pressing the flexible top sheet creates electrical contact betweenthe resistive layers, producing a switch closing in the circuit. The


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control electronics alternate voltage between the layers and pass

the resulting X and Y touch coordinates to the touchscreen

controller. The touchscreen controller data is then passed on to

the computer operating system for processing.

Resistive touch screen panels are generally more affordable but

offer only 75% clarity and the layer can be damaged by sharpobjects. Resistive touch screen panels are not affected by outside

elements such as dust or water. Resistive touchscreens are used

in food-service; retail Point-Of-Sale (POS), medical monitoring

devices, portable and handheld products, industrial process

control and instrumentation. Resistive Technology is divided into

two broad categories:

4 -Wire Resistive Touchscreen TechnologyFour-wire resistive technology is the simplest to understand and

manufacture. It uses both the upper and lower layers in the

touchscreen "sandwich" to determine the X an d Y coordinates. Typically constructed with uniform

resistive coatings of ITO on

the inner sides of the layers and silver buss bars along the edges,

the combination sets up lines of equal potential in both X and Y.

In the illustration below, the controller first applies 5V to the

back layer. Upon touch, it probes the analog voltage with the

coversheet, reading 2.5V, which represents a left -right position

or X axis.

It then flips the process, applying 5V to the covershe et, and

probes from the back layer to calculate an up-down position or Y

axis. At any time, only three of the four wires are in use.


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The primary drawback of four-wire technology is that one

coordinate axis (usually the Y axis), uses the outer layer, the

flexible coversheet, as a uniform voltage gradient. The constant

flexing that occurs on the outer coversheet with use willeventually cause microscopic cracks in the ITO coating, changing

its electrical characteristics (resistance), degrading the linearity

and accuracy of this axis.

2.1.2) 5-Wire Resistive Touchscreen Technology

In the five-wire design, one wire goes to the coversheet (E)

which serves as the voltage probe for X and Y. Four wires go to

corners of the back glass layer (A, B, C, and D). The controller

first applies 5V to corners A and B and grounds C and D,

causing voltage to flow uniformly across the screen from the top

to the bottom. Upon touch, it reads the Y voltage from the coversheet at E. Then the controller

applies 5V to corners A andC and grounds B and D, and reads the X voltage from E again.


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So, a five-wire touchscreen uses the stable bottom layer for both

X- and Y-axis measurements. The flexible coversheet acts only

as a voltage-measuring probe. This means the touchscreencontinues working properly even with non-uniformity in the

coversheet's conductive coating. The result is an accurate,

durable and more reliable touchscreen over four- and eight-wire

designs. Microscopic cracks in the coversheet coating might

occur, but they would no longer cause non-linearities as in the

case of 4 wire resistive touch screen.

2.2 Capacitive

A capacitive touch screen panel is coated with a material that

stores electrical charges. When the panel is touched, a small

amount of charge is drawn to the point of contact. Circuits

located at each corner of the panel measure the charge and sendthe information to the controller for processing. Capacitive touch

screen panels must be touched with a finger unlike resistive and

surface wave panels that can use fingers and stylus.

Capacitive touch screens have excellent clarity, and there are no

moving parts to wear out. Liquids, dirt, grease, or other

contaminants do not affect them. Unfortunately, gloved fingers

will not activate the system. It is divided into two broad

categories as follows:

2.2.1) Surface capacitive technology

In this technology, only one side of the insulator is coated with a

conductive layer. A small voltage is applied to the layer,resulting in a uniform electrostatic field. When a conductor, such


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as a human finger, touches the uncoated surface, a capacitor is

dynamically formed. The sensor's controller can determine the

location of the touch indirectly from the change in the

capacitance as measured from the four corners of the panel. As it

has no moving parts, it is moderately durable, has limited

resolution and is prone to false signals from parasitic capacitivecoupling. It is therefore most often used in simple applications

such as industrial controls and kiosks.

2.2.2) Projected capacitive technology

Projected Capacitive Touch (PCT) technology is a capacitive

technology which permits more accurate and flexible operation,

by etching the conductive layer. An X-Y grid is formed either by

etching a single layer to form a grid pattern of electrodes, or by

etching two separate, perpendicular layers of conductive material

with parallel lines or tracks to form the grid. A finger on a grid of

conductive traces changes the capacitance of the nearest traces.

This change in trace capacitance is measured and finger positionis computed.

The use of an X-Y grid permits a higher resolution than resistive

technology. Projected capacitive touch screens are clear, durable,

solid state, scratch resistant and allow gloved hand use. All these

features make them ideal for harsh, industrial, or outdoor

applications

The trend of using touch pad in smart appliances is growing day by day. Touch LCD not only provide

ease of use but also facilitate end user interface up to great extant. A touchscreen is an electronic

visual display that the user can control through simple or multi-touch gestures by touching the

screen with one or more fingers. Some touchscreens can also detect objects such as a stylus or

ordinary or specially coated gloves. The user can use the touchscreen to react to what is displayed

and to control how it is displayed (for example by zooming the text size).

Wireless links

WirelessThe term wireless means without wire, cable or any other physical connecting

link.Here in this technology the elements or devices are connected and

communicating without any physical link.

Wireless operations permit services, such as long-range communications,

that are impossible or impractical to implement with the use of wires. The

term is commonly used in the telecommunications industry to refer to

telecommunications systems (e.g. radio transmitters and receivers, remote

controls etc.) which use some form of energy (e.g.radio waves, acoustic
http://en.wikipedia.org/wiki/Electronic_visual_displayhttp://en.wikipedia.org/wiki/Electronic_visual_displayhttp://en.wikipedia.org/wiki/Multi-touch_gestureshttp://en.wikipedia.org/wiki/Stylus_(computing)http://en.wikipedia.org/wiki/Multi-touch_gestureshttps://en.wikipedia.org/wiki/Radio_waveshttps://en.wikipedia.org/wiki/Radio_waveshttps://en.wikipedia.org/wiki/Radio_waveshttps://en.wikipedia.org/wiki/Radio_waveshttp://en.wikipedia.org/wiki/Multi-touch_gestureshttp://en.wikipedia.org/wiki/Stylus_(computing)http://en.wikipedia.org/wiki/Multi-touch_gestureshttp://en.wikipedia.org/wiki/Electronic_visual_displayhttp://en.wikipedia.org/wiki/Electronic_visual_display


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energy, etc.) to transfer information without the use of wires.[1]

Information is

transferred in this manner over both short and long distances.

Wireless communication is the transfer of information between two or more

points that are not connected by an electrical conductor.

Answering the call of customers frustrated with cord clutter,

many manufacturers of computer peripherals turned to wireless technology

to satisfy their consumer base. Originally these units used bulky, highly

limited transceivers to mediate between a computer and a keyboard and

mouse; however, more recent generations have used small, high-quality

devices, some even incorporatingBluetooth. These systems have become

so ubiquitous that some users have begun complaining about a lack of wired

peripherals. Wireless devices tend to have a slightly slower response time

than their wired counterparts; however, the gap is decreasing.

Modes of wireless communication

Wireless communications can be via:

radiocommunication,

microwavecommunication, for example long-range line-of-sight viahighly directional antennas, or short-range communication,

light, visible andinfrared(IR) for exampleconsumer IRdevices such

asremote controlsor viaInfrared Data Association(IrDA). sonic, especiallyultrasonicshort range communication

electromagnetic inductionshort range communication and power

Applications

The application of wireless communicationm involvepoint-to-pointcommunication,point-to-multipoint communication,broadcasting,cellularnetworksand otherwireless networks.

Wi-Fi technology.
https://en.wikipedia.org/wiki/Wireless#cite_note-FS1037C-1https://en.wikipedia.org/wiki/Wireless#cite_note-FS1037C-1https://en.wikipedia.org/wiki/Wireless#cite_note-FS1037C-1https://en.wikipedia.org/wiki/Bluetoothhttps://en.wikipedia.org/wiki/Bluetoothhttps://en.wikipedia.org/wiki/Bluetoothhttps://en.wikipedia.org/wiki/Radiohttps://en.wikipedia.org/wiki/Radiohttps://en.wikipedia.org/wiki/Microwavehttps://en.wikipedia.org/wiki/Microwavehttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Consumer_IRhttps://en.wikipedia.org/wiki/Consumer_IRhttps://en.wikipedia.org/wiki/Consumer_IRhttps://en.wikipedia.org/wiki/Remote_controlhttps://en.wikipedia.org/wiki/Remote_controlhttps://en.wikipedia.org/wiki/Remote_controlhttps://en.wikipedia.org/wiki/Infrared_Data_Associationhttps://en.wikipedia.org/wiki/Infrared_Data_Associationhttps://en.wikipedia.org/wiki/Infrared_Data_Associationhttps://en.wikipedia.org/wiki/Ultrasoundhttps://en.wikipedia.org/wiki/Ultrasoundhttps://en.wikipedia.org/wiki/Ultrasoundhttps://en.wikipedia.org/wiki/Electromagnetic_inductionhttps://en.wikipedia.org/wiki/Electromagnetic_inductionhttps://en.wikipedia.org/wiki/Point-to-point_(telecommunications)https://en.wikipedia.org/wiki/Point-to-point_(telecommunications)https://en.wikipedia.org/wiki/Point-to-point_(telecommunications)https://en.wikipedia.org/wiki/Point-to-point_(telecommunications)https://en.wikipedia.org/wiki/Point-to-multipoint_communicationhttps://en.wikipedia.org/wiki/Point-to-multipoint_communicationhttps://en.wikipedia.org/wiki/Point-to-multipoint_communicationhttps://en.wikipedia.org/wiki/Broadcastinghttps://en.wikipedia.org/wiki/Broadcastinghttps://en.wikipedia.org/wiki/Broadcastinghttps://en.wikipedia.org/wiki/Cellular_networkhttps://en.wikipedia.org/wiki/Cellular_networkhttps://en.wikipedia.org/wiki/Cellular_networkhttps://en.wikipedia.org/wiki/Cellular_networkhttps://en.wikipedia.org/wiki/Wireless_networkhttps://en.wikipedia.org/wiki/Wireless_networkhttps://en.wikipedia.org/wiki/Wireless_networkhttps://en.wikipedia.org/wiki/Wireless_networkhttps://en.wikipedia.org/wiki/Cellular_networkhttps://en.wikipedia.org/wiki/Cellular_networkhttps://en.wikipedia.org/wiki/Broadcastinghttps://en.wikipedia.org/wiki/Point-to-multipoint_communicationhttps://en.wikipedia.org/wiki/Point-to-point_(telecommunications)https://en.wikipedia.org/wiki/Point-to-point_(telecommunications)https://en.wikipedia.org/wiki/Electromagnetic_inductionhttps://en.wikipedia.org/wiki/Ultrasoundhttps://en.wikipedia.org/wiki/Infrared_Data_Associationhttps://en.wikipedia.org/wiki/Remote_controlhttps://en.wikipedia.org/wiki/Consumer_IRhttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Microwavehttps://en.wikipedia.org/wiki/Radiohttps://en.wikipedia.org/wiki/Bluetoothhttps://en.wikipedia.org/wiki/Wireless#cite_note-FS1037C-1


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CHAPTER # 2

NUTS AND BOLTS

Sainsmart 3.2tft Display:In this project we will use 3.2TFT LCD touch screen to provide different functionality to

end user. Some of these features include:

1) In vehicle user call facility2) In vehicle car conditions facility including speed, oil gauge, head lights etc

3) In vehicle graphical display for different application

The figure below shows the 3.2TFT sainsmart Touch LCD.
http://www.elecfreaks.com/wiki/index.php?title=File:LCD_TFT01_3.2W_16.jpg


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Pin Diagram:

Procedure for LCD:

1) Set Pin RD, CS to be 1

2) Set Pin CS to be 03) Send 8Bit Command Set to 8Bit Data Bus Lower and then send 0x00 to 8 Bit Data BusUpper4) Set Pin RS to be 05) Set Pin WR to be 06) Set Pin WR to be 17) Set Pin RS to be 1After sent the command set successfully, user needs to send the data of the command asfollows;8) Still set Pin CS to be 0 and still set Pin RS, RD to be 1

9) Send 16Bit Data of the command set to all 16Bit Data Bus.10) Set Pin WR to be 011) Set Pin WR to be 112) Set Pin CS to be 1

Procedure for Touch Interfacing:
http://www.elecfreaks.com/wiki/index.php?title=File:TFT01-2.4-04.jpg


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1) Read status from Pin PEN of ADS7846; if it is 0 (touching the screen), start reading

value in the next step 2; on the other hand, if it is 1 (not touching any screen yet), reads

repeatedly.

2) Set Pin DCLK, CS, DOUT to be 0

3) Send Control Byte 0x0D to Pin DIN (MOSI) of ADS7846 to specify reading 12Bit

ACD value on the X axis.

4) Send Data 0x00 to Pin DIN (MOSI) of ADS7846. While sending out data in each bit,

ADS7846 will also shift out the ADC value to Pin DOUT(MISO). The first bit data that is

shifted out is the 11th bit at the falling edge of the second DCLK. When all 8 of DCLK

are sent out completely, it reads data on the X axis as 0x0ddddddd (d=data bit11bit5).

5) Send Control Byte 0x90 to Pin DIN (MOSI) of ADS7846 to specify reading 12Bit

ADC value on Y axis. While sending out this Control Byte, the last 5Bit data ADC on X

axis will be also sent out. It begins with bit4 to bit0 and Data is arranged as 0xddddd000

(d=data bit4bit0).

6) Send Data 0x00 to Pin DIN (MOSI) of ADS7846. While sending out data in each bit,

ADS7846 will also shift out ADC value to Pin DOUT(MISO). The first bit data that is

shifted out is the 11th bit at the falling edge of the second DCLK. When all 8 of DCLK is

sent completely, it reads on the Y axis as 0x0ddddddd (d=data bit11 bit5).

7) Send Data 0x00 to Pin DIN (MOSI) of ADS7846. While sending out Data, the last 5Bit

ADC data on the Y axis will be also sent out. It begins with bit4 to bit 0 and Data is

arranged as 0xddddd000 (d=data bit4 bit0).

8) When the ADC values on both axes are read completely, need to set Pin CS to be 1 to

finish reading values from ADS7846.

9) If user wants to read the new value, repeatedly start the step 1.10) After got the ADC value on each axis completely, user needs to arrange the values.The variable that is used to store the ADC value should be read as 16Bit. When the first7Bit of data ADC is read, it is stored in the 16Bit variable as 0x000000000ddddddd ; andthe next 5Bit when it is stored in the 16bit variable is 0x000000000ddddddd. Then shiftout the first 7Bit data that is read to the left side 5Bit and then shift out the next 5Bit thatis read to the right side 3Bit. Finally, must OR(|) both sets together, user got 12Bit dataADC of the axis that is read as 0x000ddddddddddddd. This is the complete value and isready to use.


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THE 27MHz TRANSMITTER

In this discussion we cover 27MHz transmitters and receivers as found in remote

control cars,

aeroplanes, walkie talkies and some of the older-style garage door openers.

We have provided a number of circuits so you can work out the best type for your

application and

these circuits will also help you understand which components are critical and which

components can

be changed.

It's a matter of looking at each circuit and seeingthe general layout, and comparing it

to the other

circuits. In this way you are building up a conceptof "building blocks" and this is the

basis to learning

electronics.

Talking Electronics does not provide any kits for these circuits as the products (toy

cars, wireless

doorbells etc) are readily available in toy shops, hobby shops and many of the $2.00

"junk Shops."

You cannot buy many of the special components and the cost of the completed item

is less than

buying the components!

Let's start:

6 bands (or frequencies) were allocated for the 27MHz band,

Channel Frequency

1 26.995

2 27.045

3 27.095

4 27.145

5 27.195

6 27.255

and these were very popular for transmission - especially in countries where

transmitting was strictly

controlled.

Both 27MHz and 49MHz circuitry produced very low cost devices and they are still

available. But you


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. The first two circuits (figs 1& 2) form a single-channel transmitter-receiver link.

The second receiver

(fig 7) uses a split supply to power a motor in theforward and reverse direction (it

uses the same

transmitter as shown in fig 1). The third transmitter & receiver, (figs 12 & 22) is a

multi-channel design,

with a chip in the receiver. Then we cover a 27MHz walkie talkie. This is a 4

transistor model. It uses

the same type of super-regenerative front-end as our receiver circuits and injects

Amplitude Modulated

(AM) audio onto the signal. The result is a very noisy transmission but a very

effective way to achieve

both transmission and reception with the minimum ofcomponents. Most of the parts

have a dual

function, operating in both transmit and receive mode. This makes the circuit very

efficient,

component-wise.

Before we start, some of the Japanese transistors have either a very high frequency

capability or a

very high collector current. These transistors needto have an equivalent for the

circuit to work

successfully. Here is a list of some of the type you will come across and some

equivalents


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Fig 1 shows a simple 27MHz transmitter producing a carrier.


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The 27MHz transmitter PC board

This means it produces an unmodulated 27MHz signal and when picked up by a

receiver, such as

shown in fig 2, the result is a clean, noise-free reception. To increase the output of

the transmitter, the

390R resistor is replaced by a 220R. This increasesthe current from 7mA to 12mA.

The resistor could

be decreased to 150R for more output .


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When the transmitter is off, the car moves forward.When the transmitter is on, the

car reverses and

moves in a circular pattern. This allows the operator to guide the car around

obstacles. It's a very

awkward way to control a car and although it is very simple and clever, it is not

really successful in

practice. We will not be going into the mechanics of how the car steers, only the factthat the

transmitter causes the motor to reverse direction. In place of the motor you could use

a relay or two

separate motors to carry out a number of functions and we will show how the circuit

can be modified to

do this.

The receiver works on a "tone," "no-tone" principlebut the transmitter doesn't

actually send a tone asthis would require additional circuitry. What happens is the receiver picks up

random noise from the

airwaves when the transmitter is not operating and this functions as the tone part of

the reception. This

random noise is amplified by the second transistor and passed to a 0.47u electrolytic

that keeps the

third transistor in conduction for the majority of the time. The operation of this will

be discussed later.


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The 10u on the output of the third transistor keepsthe output low for the short

periods when the third

transistor is not low. The motor is connected in a bridge formation via four

transistors and these

change the polarity of the supply to the motor.

When the transmitter is operating, and the receiveris within range, it picks up a

27MHz carrier that

over-rides the random noise and produces a CARRIER.This means the second

transistor will not see

any noise and thus the 0.47u electrolytic will charge and turn off the third transistor.

The 10u will

charge via the 2k2 and the input to the bridge willchange from a LOW to a HIGH.

This will turn on the

opposite half of the bridge to supply current to the motor in the reverse direction.

Now we will cover the circuit in detail.

HOW THE TRANSMITTER WORKS

The transmitter is a very simple crystal oscillator. The heart of the circuit is the

tuned circuit consisting

of the primary of the transformer and a 10p capacitor. These two components

oscillate when a voltage

is applied to them. The frequency is adjusted by a ferrite slug in the centre of the coil

until it is exactly

the same as the crystal. The crystal will then maintain the frequency over a wide

range of temperature

and supply voltage fluctuations. The transistor is configured as a common emitter

amplifier. It has a

resistor on the emitter for biasing purposes but the 82p across the 390R effectively

takes the emitterto

the negative rail as far as the signal is concerned. The 390R resistor prevents a high

current passing

through the transistor as the resistance of the transformer is very low. The tuned

circuit operates at

exactly the third harmonic (also called the third overtone - an overtone is a multiple

of a fundamental

frequency) of the crystal so that the crystal will oscillate at its third overtone

(27MHz) and in-turn, keep


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the frequency of the circuit stable. The transformer in the collector of the transistor

performs two

functions. 1. It matches the impedance of the transistor to the impedance of the

antenna, and 2.

Creates a resonant circuit at 27MHz to make sure the crystal oscillates at this

frequency. You can see

the transformer creates a resonant circuit by the fact that it has a capacitor across the

primary winding.

These two components create a "resonant" or "tuned " circuit and this is where the

circuit "gets its

frequency."

The crystal has a fundamental of about 9MHz and it will oscillate at this frequency

unless assisted to

oscillate at a higher frequency. This is done by the tuned circuit oscillating at

27MHz.

Now we will look at the impedance-matching feature of the transformer.

The impedance of the output of the transistor is about 1k to 5k and this means it is

the impedance

(resistance) "it works at." In other words, it is the characteristic impedance of the

transistor in this type

of stage. The impedance of a whip antenna is about 50 ohms and the transformer

matches these two

by having a TURNS RATIO.

The primary has about 12 turns and the secondary about 3 turns. This provides part

of the matching

requirement. The `pi' network, made up of the 150p,15 turn air-cored coil and 100p

capacitor assists

further in matching the output of the transformer to the antenna. When the power is

applied, the

transistor turns on fairly hard due to the 82p in the emitter being uncharged.

This puts a pulse of energy through the 10p and as the transistor turns off slightly

due to the 82p

charging, the energy in the 10p capacitor is passedto the primary of the transformer

to start the

27MHz cycle. The action of the emitter rising and falling during start-up, allows the

base to rise andfall

and this puts a pulse on the crystal to start it oscillating.


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The frequency of oscillation OF THE CIRCUIT is generated by the tuned circuit in

the primary of the

transformer and the crystal merely keeps the circuit operating at exactly 27.145MHz

(or 27.240MHz,

depending on the frequency of the crystal). The turns ratio of the transformer

converts a high voltage

waveform (that has little current) from the transistor, into a low voltage waveform

with a higher current.

This is exactly what the antenna requires. But before the signal passes into the

antenna it goes

through the pi network, then an 8 turn Radio Frequency Choke. This is 8 turns of

enamelled wire

wound on a ferrite core and is called a base-load for the antenna.

The result is a 27MHz frequency called a CARRIER. The carrier produces a clean

spot on the band

that is free from background noise.

HOW THE RECEIVER WORKS

The first thing you have to realize is the receiveris really a transmitter. It's a very

weak transmitter and

delivers a low level signal to the surroundings viathe antenna. When another signal

(from the

transmitter) comes in contact with the transmissionfrom the receiver it creates an

interference pattern

that reflects down the antenna and into the first stage of the receiver.

The receiver is a super-regenerative design. This means it is self-oscillating (or

already oscillating) and

makes it very sensitive to nearby signals. It is much more sensitive than receiving a

signal and making

it oscillate a transistor.

A super-regenerative design is not universally usedbecause it is much more noisy

than conventional

reception and is not suitable for voice transmission. However it is used in simple

walkie-talkies and this

is why they are so noisy - as will be shown at the end of this article. When a signal

of the same

frequency as the super-regenerative circuit passes near the antenna, the circuit has

difficulty radiating


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a signal.

This means the circuit current VARIES. These variations appear across the 2k2 load

resistor as a

change in voltage and the signal is picked off via a 100n capacitor and passed to the

second and third

stages for amplification.

The 22n across the first stage is designed to remove the high-frequency component

from the

waveform. If this were not present, the circuit would never change state. The

receiver is tuned to the

frequency of the crystal in the transmitter via a slug-tuned coil in the collector.

When the transmitter is off, the receiver picks up background noise and amplifies it

to produce

random-noise. This is amplified by the second transistor and passed to the third via a

0.47u

electrolytic. This electrolytic is designed to keepthe third transistor ON for the major

part of the time

and it does this in a very clever way. We will assume the supply has just been turned

on and the

second transistor is not receiving a signal. The 0.47u will be uncharged and it will

charge via the 10k

collector resistor and the base-emitter junction ofthe third transistor.

The action of the current flowing through the base of the third transistor will turn it

ON but after ashort

time the electrolytic will be fully charged and thecurrent will cease and the transistor

will turn off. A

10u on the collector of the third transistor will then begin to charge via the 2k2

resistor and after a

period of time called the DELAY TIME, the output will be HIGH and change the

state of the bridge. But

if a signal is present on the collector of the second transistor, (in our case this will be

background

hash), the voltage on the collector will be rising and falling. When the voltage goes

low, it takes the

positive end of the 0.47u low and the other end must follow.

The voltage on the negative end will go below the negative rail and at -0.7v it gets

clamped by the


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diode. This means the electrolytic gets discharged very rapidly when the second

transistor turns on.

The result is the electrolytic takes a long time tocharge and a short time to discharge,

even when

random noise (hash) is being processed.

The action of the 0.47u is amazing and will be explained in more detail in a moment.

During the short

periods of time when the third transistor is not turned on, the 10u on the collector

will take over and

hold the signal low. It's only when a long durationof silence is encountered, that the

circuit will change

state. This period of silence is when the transmitter turns ON and the time is very

short in real terms.

Transistor Q3 is called the switching transistor. It changes between HIGH and LOW

to create the

forward and reverse direction. The switching transistor feeds two driver transistors,

Q4 and Q9. Each

of these drives two output transistors. Q4 drives Q6 and Q7. Q9 drives Q5 and Q8.

Follow these transistors on the circuit and you will see how the supply is directed to

the motor, firstly in

one direction and then the other.

The printed circuit board is quite complex because of the number of driver

transistors. But since these

cost less than 2 cents when bought in the million, it is not cheaper to use a chip.

HOW THE 0.47u WORKS

The 0.47u electrolytic on the base of the third transistor needs explaining as its

operation is very

clever.


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Charging the 0.47u electrolytic

is represented as a battery.

The electrolytic is simply a tiny re-chargeable battery and when the circuit first turns

on, it is

uncharged. The charging current passes through the base-emitter junction of the

third transistor and

keeps it ON as shown in fig: 3. If the electrolyticis allowed to fully charge, the

current will fall to zero

and the third transistor will turn off. But the second transistor discharges the

electrolytic quickly before

it has time to fully charge. It does this by turning ON. How the electrolytic

discharges is shown in fig: 4.

The only components involved in the discharge are Q2 and the diode. Transistor Q2

is turned on and it

will have zero volts (0.3v) on the collector.

Discharging the 0.47u electrolytic.

This means the positive lead of the electrolytic (equivalent to the positive terminal of

the battery) will

drop from say nearly 3v, to 0.3v. The negative leadmust follow and normally it

would be at -2.7v. Yes,

the negative lead would have a negative voltage on it relative to the 0v rail, if the

diode was not


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present. BUT the diode on the negative lead gets turned on as soon as the voltage on

the negative

lead falls to -0.7v and prevents it going below -0.7v. As the positive lead falls, the

energy in the

electrolytic is quickly discharged through the diode and when the second transistor

turns OFF, the

electrolytic is ready for charging, through the 10kresistor.

PIC MICROCONTROLLER

PIC18F452PIC32MX250F128B

The PIC16 series of microcontrollers have been around for many years. Although they are

excellent general-purpose microcontrollers, they have certain limitations. For example, the

program and data memory capacities are limited, the stack is small, and the interrupt

structure is primitiveall interrupt sources share the same interrupt vector. The PIC16 series

of microcontrollers also do not provide direct support for advanced peripheral interfaces,

such as USB and CAN bus, and it is rather complex to interface to such devices easily. The

instruction set of these microcontrollers is also limited. For example, there are no

instructions for multiplication or division and branching is rather simple and is made out of a

combination of skip and goto instructions. Microchip Inc. has developed the PIC18 series

of microcontrollers for high-pin-count, high-d ensity, and complex applications.

Figure 2.1 shows the current PIC microcontroller family of products. At the lowest end of

the family, we have the PIC10 microcontrollers, operating at approximately 5 MIPS and with

small form factors, less memory, and a low cost. Then we have the PIC12 and PIC16 series

of micro -controllers with midrange architectures, 58 MIPS operating performance, and

reasonable size of memory. The microcontrollers of the PIC18 family are advanced high-

performance devices, with 1016 MIPS, and offer a large amount of memory with various

on-chip peripheral support modules. As shown in Figure 2.1, the higher end of the family

consists of 16-bit devices, such as the PIC24 and the dsPIC, and 32-bit devices, such as the

dsPIC33 and the PIC32 series.


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The PIC18 microcontroller family consists of three architectures: the standard PIC18F series,

the PIC18J series, and the PIC18K series. PIC18J series are 1012 MIPS, low-voltage, high-

performance microcontrollers with integrated USB, Ethernet, or LCD. PIC18K series are 16

MIPS, high-performance, and low-power devices.

The PIC18F microcontrollers can be used in cost-efficient solutions for general-purpose

applications written in C, using a real-time operating system (RTOS), and require complex

communication protocol stack, such as TCP/IP, CAN, USB, or ZigBee. PIC18F devices

provide flash program memory in sizes from 8 to 128 KB and data memory from 256 to 4

KB, operating at 2.05.0 V at speeds from DC to 40 MHz.

The basic features of the PIC18F series of microcontrollers are as follows:

77 instructions.

PIC16 source code compatible.

Program memory addressing up to 2 MB

Data memory addressing up to 4 KB

DC to 40-MHz operation


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8 8 hardware multiplier

Interrupt priority levels

16-bit wide instructions, 8-bit wide data path Up to two 8-bit timer/counters

Up to three 16-bit timer/counters

Up to four external interrupts

High-current (25 mA) sink/source capability

Up to five capture/compare/pulse width modulation (PWM) modules

Master synchronous serial port module (serial peripheral interface [SPI] and

I2C modes)

Up to two universal synchronous-asynchronous receiver-transmitter (USART)

modules

Parallel slave port (PSP)

Fast 10-bit analog-to-digital (A/D) converter

Programmable low-voltage detection (LVD) module

Power-on reset (POR), power-up timer (PWRT), and oscillator start-up timer

(OST)

Watchdog timer (WDT) with on-chip RC oscillator

In-circuit programming

In addition, some microcontrollers in the family offer the following special features:

Direct CAN 2.0B bus interface

Direct USB 2.0 bus interface

Direct LCD control interface

TCP/IP interface

ZigBee interface

Direct motor control interface

There are many devices in the PIC18F family, and most of them are source compatible with

each other. Table below gives the characteristics of some of the popular devices in this family.

In this chapter, the PIC18FXX2 microcontrollers are chosen for detailed study. Most of the

other microcontrollers in the family have similar architectures.


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Pic18 Family Architecture:As shown in Table 2.1, the PIC18FXX2 series consists of four devices. PIC18F2X2

microcontrollers are 28-pin devices, and PIC18F4X2 microcontrollers are 40-pin devices. The

architectures of both groups are almost identical except that the larger devices have more I/O

ports and more A/D converter channels. In this section, we shall be looking at the

architectureof the PIC18F452 microcontrollers in detail. The architectures of other standard

PIC18F series microcontrollers are very similar, and the knowledge gained in this section

should be enough to understand the operation of other PIC18F series microcontrollers.

The pin configuration of the PIC18F452 microcontroller (DIP package) is shown in Figure.

This is a 40-pin microcontroller housed in a DIL package and has a pin configuration similar

to that of the popular PIC16F877.

Figure shows the internal block diagram of the PIC18F452 microcontrollers. The CPU is at the

center of the diagram and consists of an 8-bit ALU, a n 8-bit working accumulator register

(WREG), and a 8 8 hardware multiplier. The higher byte and the lower byte of a

multiplication are stored in two 8-bit registers called PRODH and PRODL, respectively.


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The program counter and the program memory are shown at the top left corner of the diagram.

Program memory addresses consist of 21 bits and are capable of accessing 2 MB of program

memory locations. PIC18F452 has only 32 KB of program memory, which requires only 15

bits; thus, the remaining six address bits are redundant and not used. A table pointer provides

access to tables and to the data stored in the program memory. The program memory containsa 31-level stack, which is normally used to store the interrupt and subroutine return addresses.

The data memory can be seen at the top central part of the diagram. The data memory address

bus is 12 bits wide and is capable of accessing 4 KB of data memory locations. As we shall

study later, the data memory consists of the SFR and the general-purpose registers (GPR), all

organized in banks.


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The bottom part of the diagram shows the timers/counters, capture/compare/PWMregisters, USART, A/D converter, and the EEPROM data memory. PIC18F452 consists of

Four counters/timers

Two capture/compare/PWM modules

Two serial communication modules

Eight 10-bit A/D converter channels

256-byte EEPROM

The oscillator circuit is located at the left-hand side of the diagram. This circuit consists of

PWRT

OST

POR

WDT

Brown-out reset (BOR)

Low-voltage programming

In-circuit debugger (ICD)

PLL circuit

Timing generation circuit

The PLL is new to the PIC18F series, and it provides the option of multiplying theoscillator frequency to speed up the overall operation. The WDT can be used to force arestart of the microcontroller in the event of a program crash. The ICD is useful during

program development, and it can be used to return diagnostic data, including the registervalues, as the microcontroller is executing a program.

The I/O ports are located at the right-hand side of the diagram. PIC18F452 consists of fiveparallel ports named PORTA, PORTB, PORTC, PORTD, and PORTE. Most port pins havemultiple functions. For example, PORTA pins can be used as either parallel I/O or analoginputs. PORTB pins can be used as either parallel I/O or interrupt inputs.

Code Memory Organization:

The program memory map is shown in Figure 2.4. Each PIC18F member has a 21-bitprogram counter and hence is capable of addressing 2 MB of memory space. User memory

space on the PIC18F452 microcontroller is 00000H to 7FFFH. Accessing a nonexistentmemory location (8000H to 1FFFFFH) will cause a read of all 0s. The reset vector where the


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program starts after a reset is at address 0000H. Addresses 0008H and 0018H are reservedfor the vectors of high-priority and low-priority interrupts, respectively, and interrupt serviceroutines must be written to start at one of these locations.

The PIC18F microcontroller has a 31-entry stack that is used to hold the return addressesfor subroutine calls and interrupt processing. The stack is not a part of the program or a datamemory space. The stack is controlled by a 5-bit stack pointer, which is initialized to 00000after a reset. During a subroutine call (or interrupt), the stack pointer is first incremented, andthe memory location pointed to by the stack pointer is written using the contents of the

program counter. During a return from a subroutine call (or interrupt), the memory locationpointed to by the stack pointer is decremented. Program memory is addressed in bytes andinstructions are store d as 2 or 4 bytes in programmemory. The least significant byte of aninstruction word is always stored in an even addressof the program memory.

An instruction cycle consists of four cycles: A fetch cycle begins with the programcounter incrementing in Q1. In the execution cycle, the fetched instruction is latched into theinstruction register in cycle Q1. This instruction is then decoded and executed during the Q2,Q3, and Q4 cycles. A data memory location is read during Q2 and written during Q4.


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Data Memory Organization:The data memory map of the 18F452 microcontroller is shown in Figure below. The data

memory address bus is 12 bits, with the capability of addressing up to 4 MB. The memory ingeneral consists of 16 banks, each of 256 bytes. PIC18F452 has 1536 bytes of data memory(6 banks 256 bytes each) occupying the lower end of the data memory. Bank switching isdone automatically when using a high-level language compiler, and thus the user need notworry about selecting memory banks during programming.


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The special function register (SFR) occupies the upper half of the top memory bank.SFR contains registers that control the operations of the microcontroller, such as the

peripheral devices, timers/counters, A/D converter, interrupts, USART, and so on.

Input Output Ports:

The parallel ports of the 18F family are very similar to those of the PIC16 series. Thenumber of I/O ports and port pins varies depending on the PIC18F family member used, butall versions have at least PORTA and PORTB. The pins of a port are labeled as RPn, whereP is the port letter and n is the port bit number. For example, PORTA pins are labeled RA0to RA7, PORTB pins are labeled RB0 to RB7, and so on.

When working with a port, we may want to

Set port direction

Set an output value

Read an input value Set an output value and then read back the output value

The first three operations are the same between the PIC16 and the PIC18F series. In someapplications, we may want to send a value to the port and then read back the value just sent.In the PIC16 series, there is a weakness in the port design a nd the value read from a portmay be different from the value just written to it. This is because the reading is the actual

port bit pin value, and this value could be changed by external devices connected to the portpin. In the PIC18F series, a latch register (e.g., LATA for PORTA) is introduced to the I/Oports to hold the actual value sent to a port pin. From the port, the latched value is read,

which is not affected by any external devices.

Port-A:

In PIC18F452 microcontroller, PORTA is 7 bits wide and port pins are shared with otherfunctions. Table 2.6 shows the PORTA pin functions.

The architecture of PORTA is shown in Figure. There are three registers associated withPORTA:

Port data registerPORTA


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Port direction registerTRISA

Port latch registerLATA

PORTA is the name of the port data register. The TRISA register defines the direction ofPORTA pins, where logic 1 in a bit position defines the pin as an input pin, and a 0 in a bit

position defines it as an output pin. LATA is the output latch register, which shares the samedata latch as PORTA. Writing to one is equivalent to writing to the other one as well. Butreading from LATA activates the buffer at the top of the diagram, and the value held inPORTA/LATA data latch is transferred to the data bus, independent of the state of the actualoutput pin of the microcontroller.

Bits 0 through 3 and 5 of PORTA are also used as analog inputs. After a device reset,these pins are programmed as analog inputs, and RA4 and RA6 are confi gured as digitalinputs.

To program the analog inputs as digital I/O, the ADCON1 register (A/D register) must be

programmed accordingly. Writing 7 to ADCON1 configures all PORTA pins as digital I/O.


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The RA4 pin is multiplexed with the Timer 0 clock input (T0CKI). This is a Schmitttrigger input and an open drain output.

RA6 can be used as a general-purpose I/O pin, or as the OSC2 cl ock input, or as a clockoutput providing FOSC/4 clock pulses.

Port-B:

In the PIC18F452 microcontroller, PORTB is an 8-bit bidirectional port shared withinterrupt pins and serial device programming pins. Table below gives the PORTB bit

functions.PORTB is controlled by registers, and they are as follows:

Port data registerPORTB

Port direction registerTRISB

Port latch registerLATB

The general operation of PORTB is similar to that of PORTA. Figure 2.24 shows thearchitecture of PORTB. Each port pin has a weak internal pull-up, which can be enabled byclearing bit RBPUof register INTCON2. These pull-ups are disabled on a POR and when the

port pin is configured as an output. On POR, PORTB pins are configured as digital inputs.

Internal pull-ups allow input devices, such as switches, to be connected to PORTB pinswithout the use of external pull-up resistors. This saves cost because of the reducedcomponent count and less wiring requirements.

Port pins RB4RB7 can be used as interrupt on change inputs, whereby a change on anyof pins 47 causes an interrupt flag to be set. The interrupt enable and flag bits RBIE andRBIF are in register INTCON.


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Port-C,D,E:

In addition to PORTA and PORTB, PIC18F452 has 8-bit bidirectional ports PORTC andPORTD, and 3-bit PORTE. Each port has its own data register (e.g., PORTC), data direction

register (e.g., TRISC), and data latch register (e.g., LATC). The general operation of theseports is similar to PORTA.


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In the PIC18F452 microcontroller, PORTC is multiplexed with several peripheral

functions, as shown in Table 2.8. On a POR, PORTC pins are configured as digital inputs.In the PIC18F452 microcontroller, PORTD has Schmitt Trigger input buffers. On a POR,

PORTD is configured as digital inputs. PORTD can be configured as an 8-bit PSP (i.e.,microprocessor port) by setting bit 4 of the TRISE register. Table 2.9 shows functions ofPORTD pins.

In the PIC18F452 microcontroller, PORTE is only 3 bits wide. As shown in Table 2.10,port pins are shared with analog inputs and parallel slave port read/write control bits. On aPOR, PORTE pins are configured as analog inputs, and register ADCON1 must be

programmed to change these pins to digital I/O.


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Serial Communication (USART):

Hardware USART functions enable RS232 type serial communication to be implementedusing the hardware USART module of the microcontroller. In general, hardware-based

USART can give faster and more reliable communication. In addition, the processor cancarry out other tasks while the USART is handling the serial communication.

C18 compiler provides the USART functions given in Table 4.22 (in microcontrollerswith more than one USART a number is added to the end of these functions to identify theUSARTs). The header file usart.h must be defined at the beginning of a program usingthese functions.

The definition of these functions is given in the below table.

BusyUSART:This function returns a 1 if the USART transmitter is busy transmitting acharacter. This function should be checked before sending a new byte to the USART. Thefunction returns a 0 if the USART transmitter is idle.

CloseUSART: This function disables the USART.

DataRdyUSART: This function returns a 1 if data is available in the USART readbuffer. A 0 indicates that data is not available in the read buffer.

getcUSART: This function reads a byte from the USART buffer. An example is givenbelow:

int result;result = getcUSART( );

getsUSART: This function reads a string of characters from the USART. This functionwaits and reads a specified number of characters. There is no timeout and the program willwait forever if the specified numbers of characters are not received. An example is given

below to show how this function can be used:

char buff[20];


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getsUSART(buff, 6); // Wait to receive 6 characters

OpenUSART: This function configures the USART. Two arguments are required: aconfiguration argument called config and an integer called spbrg, which specifies the valueto be written to the baud rate generator register to determine the baud rate.config

Interrupt on transmission:USART_TX_INT_ON Transmit interrupt ONUSART_TX_INT_OFF Transmit interrupt OFF

Interrupt on reception:USART_RX_INT_ON Receive interrupt ONUSART_RX_INT_OFF Receive interrupt OFF

USART mode:USART_ASYNCH_MODE Asynchronous modeUSART_SYNCH_MODE Synchronous mode

Transmission width:`USART_EIGHT_BIT 8-bit transmit/receiveUSART_NINE_BIT 9-bit transmit/receive

Slave/Master selectUSART_SYNC_SLAVE Synchronous slaveUSART_SYNCH+MASTER Synchronous master

Reception mode:USART_SINGLE_RX Single receptionUSART_CONT_RX Continuous reception

Baud rate:USART_BRGH_HIGH High baud rateUSART_BRGH_LOW Low baud rate

spbrg:

This is the value written onto the baud rate generator register to define the baud rate to beused. The formula for the baud rate is as follows:

For High Speed (USART_BRGH_HIGH),Baud = FOSC/[16 * (spbrg + 1)]

or

spbrg = FOSC/(16 * baud) 1


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and

For Low Speed (USART_BRGH_LOW),Baud = FOSC/[16 * (spbrg + 1)]

or

spbrg = FOSC/(64 * baud) 1,where FOSC is the microcontroller clock frequency.

putcUSART: This function sends a byte to USART.

putsUSART: This function sends a string of characters to USART from the datamemory.

An example is given below:

putrsUSART("My Computer");putrsUSART: This function sends a string of characters to USART from the programmemory.

baudUSART: This function sets the baud rate configuration bits for enhance d USARToperation. The valid arguments can be formed from bitwise AND of the followingdefinitions:

Clock idle state:BAUD_IDLE_CLK_HIGH Clock idle state is high levelBAUD_IDLE_CLK_LOW Clock idle state is low level

Baud rate generation:BAUD_16_BIT_RATE 16-bit baud rate generationBAUD_8_BIT_RATE 8-bit baud rate generation

RX pin monitoring:BAUD_WAKEUP_ON RX pin monitoredBAUD_WAKEUP_OFF RX pin not monitored

Baud rate measurement:

BAUD_AUTO_ON Autobaud rate measurement enabledBAUD_AUTO_OFF Autobaud rate measurement disabled


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MPLABXThere are several C compilers on the market for the PIC18 series of

microcontrollers. Most of the features of these compilers are similar, and they can

all be used to develop C-based high-level programs for the PIC18 series ofmicrocontrollers.

Some of the popular C compilers used in the development of commercial, industrial,

and edu-cational PIC18 microcontroller applications are as follows:

mikroC C compiler

PICC18 C compiler

CCS C compiler

MPLAB C18 C compiler

mikroC C compiler has been developed by MikroElektronika( Web site:http://www.mikroe.com) and is one of the easy-to-learn compilers with rich

resources, such as a large number of library functions and an integrated development

environment with built-in simulator and an in-circuit-debugger (e.g., mikroICD). A

demo version of the compiler with a 2K-program limit is available from

MikroElektronika.

PICC18 C compiler is another popular C compiler developed by Hi-Tech Software(

Web site: http://www.htsoft.com). This compiler has two versions: the standard

compiler and the professional version. A powerful simulator and an integrateddevelopment environment ( Hi-Tide) are provided by the company. PICC18 is

supported by the Proteus simulator (http://www.labcenter.co.uk), whichcan be used

to simulate PIC microcontroller-based systems.

A limited-period demo version of this compiler is available from the developers

Web site.

CCS C compiler has been developed by Custom Computer Systems Inc.( Web site:

http://www.ccsinfo.com). The company provides a limited-period demo version of

their compiler. CCS compiler provides a large number of built-in functions andsupports an in-circuit-debugger (e.g., ICD-U40), which aids greatly in the

development of PIC18 microcontroller-based systems.

MPLAB C18 C compiler is a product of Microchip Inc. ( Web site:http://www

.microchip.com). An evaluation version with limited functionality is available from

the Microchip Web site. MPLAB C18 includes a simulator and supports hardware

and software development tools such as in-circuit-emulators (e.g., ICE2000) and in-

circuit-debuggers (e.g., ICD2 and ICD3). In this book, we will be using the MPLAB

C18 compiler for all the projects.MPLaB C18 Compiler
http://www/http://www/http://www/http://www/


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MPLAB C18 compiler (or the C18 compiler) is one of the mostpopular C compilers

available for thePIC18 series of microcontrollers. This compiler has been developed

by Microchip Inc. An evaluation version (student version) of the compiler is

available from the Microchip Web site free of charge. This evaluation version

includes all functionality of the full version of the compiler for the first 60 days.

However, some optimization routines are disabled after 60 days, and PIC18

extended mode (extended instruction set and indexed with literal offset addressing)

is not supported after 60 days.

MPLAB C18 is a cross compiler, where programs are developed on a PC and are

then loaded to the memory of the target microcontroller using a suitable

programming device.

The installation and use of the MPLAB C18 compiler and detailsof programming

using the compiler are given in this chapter.


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CHAPTER #3

IMPLEMENTATION

TOUCH DISPLAY OPERATIONA resistive touch screen is constructed with two transparent layers coated with a

conductive materialstacked on top of each other. When pressure is applied by a

finger or a stylus on the screen, the top layer makes contact with the lower layer.

When a voltage is applied across one of the layers, a voltage divider is created. The

coordinates of a touch can be found by applying a voltage across one layer in the Y

direction and reading the voltage created by the voltage divider to find the Y

coordinate, and then applying a voltage across the other layer in the X direction and

reading the voltage created by the voltage divider to find the X coordinate.

Detecting a TouchTo know if the coordinate readings are valid, there must be a way to detect whether

the screen is being touched or not. This can be done by applying a positive voltage

(VCC) to Y+ through a pullup resistor and applying ground to X. The pullupresistor must be significantly larger than the total resistance of the touch screen,

which is usually a few hundred ohms. When there is no touch, Y+ is pulled up to the

positive voltage. When there is a touch, Y+ is pulled down to ground as shown in

Figure 1. This voltage-level change can be used to generate a pin-change interrupt.


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TOUCH SCREEN READING

Reading a 4-Wire ScreenA 4-wire resistive touch screen is constructed as shown in Figure 2.

The x and y coordinates of a touch on a 4-wire touch screen can be read in two steps.

First, Y+ is driven high, Yis driven to ground, and the voltage at X+ is measured.

The ratio of this measured voltage to the drive voltage applied is equal to the ratio of

the y coordinate to the height of the touch screen. The y coordinate can be calculatedas shown in Figure 3. The x coordinate can be similarly obtained by driving X+

high, driving X to ground, and measuring the voltage at Y+. The ratio of this

measured voltage to the drive voltage applied is equal to the ratio of the x coordinate

to the width of the touch screen. This measurement scheme is shown in Figure 3.


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Reading an 8-Wire ScreenAn 8-wire resistive touch screen is constructed as shown in Figure 4.

In comparison to a 4-wire touch screen, an 8-wire touch screen adds sense wires to

the end of each of the conductive bars. This allows any voltage offset created by the

wiring or drive circuitry to be calibrated out during operation. An 8-wire touch

screen is calibrated by measuring voltage extremes on either coordinate. First, Y+


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drive is driven high and Y drive is driven low. The corresponding voltages

measured at Y+ sense and Y sense are denoted VYmax and VYmin. A similar

procedure yields VXmax and VXmin. These are the maximum and minimum

possible voltages across each coordinate.The coordinates of a touch on an 8-wire

touch screen can be read by first driving Y+ drive high, driving Ydrive to ground,

and reading the voltage at X+ sense. Using the maximum and minimum results

obtained during calibration, the y coordinate can be calculated as shown in the

equations in Figure 5. The x coordinate can be obtained by driving X+ drive high,

driving X drive to ground, and reading the voltage at Y+ sense. This process is

shown in Figure 5.


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Chapter # 4

APPLICATIONS

Security systemRobotics have been a staple of advanced manufacturing for over half a

century. As robots and their peripheral equipment become more

sophisticated, reliable and

miniaturized, these systems are

increasingly being utilized for military

and law enforcement purposes.

Military and battlefield applicationscontinue to grow at an accelerated

pace due to demand fueled by

government investment. Over the past

decade, we have seen increasing

levels of investment in autonomous

vehicles used for surveillance and

security, says Rush LaSelle, Vice

President and General Manager withAdept Technology Inc. (Pleasanton, California) Applications range from

monitoring perimeters of secured areas such as airports to acting as a night

watchman.

Robots go to WarMobile robotics play an increasingly important role in military matters, from

patrol to dealing with potential explosives. With suitable sensors and

cameras to perform different missions, mobile robots are operated remotely

for reconnaissance patrol and relay back video images to an operator, says

Dr. Andrew Goldenberg, PhD, Chief Executive Officer and President of

Engineering Services Inc. (ESI, Toronto Ontario, Canada) Robots can

neutralize suspicious objects that may explode. The platform has a robot

arm to pick up explosives or suspected hazards in military or civilian

settings.

Goldenberg goes on to say, The mobile robotic platform is mounted on a

rectangular box with electronic equipment. The platform moves on wheels or


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tracks, or both, and is usually battery-powered. Communication equipment

and sensors can detect images, sounds, gases and other hazards. The

communication systems read sensors and relay that information to the

operator.

Robotics help meet challenges posed by the specter of urban terrorism.

Instead of having people get close to hazards such as unattended objects

or car bombs, robots are used. If an operator concludes a dangerous object

might explode, the robot could neutralize that object by shooting to detonate

it, Goldenberg says. Mobile robots detect and explode in-ground mines or

improvised explosive devices. These same mobile robotic systems are used

for neutralizing or exploding forgotten ordnance and mines after conflicts

cease.

Autonomy or ControlThe level of autonomy separates industrial robotics from their battlefield

counterparts. Mobile robotic platforms are operated remotely and do not

have the autonomy of industrial robots. Security robotic systems are under

the total control of the operator, typically military personnel, says

Goldenberg. Security robots have not yet been made autonomous, given

the purpose of the vehicles, especially if armed. Due to a handful of

instances of friendly fire, the trend has been against providing security robot

systems the autonomy of their industrial equivalent, Goldenbergre calls.


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Consequently, operator fatigue results from people directing mobile robotic

systems denied industrial-strength autonomy, says Goldenberg. I have

heard about concerns with operators of military robots being over-loaded

and fatigued while controlling the robot. The robot is given some intelligence,

but that intelligence is limited.

The limited intelligence extends to networking the mobile robots with global

positioning satellites. (GPS) Again Andrew Goldenberg: Mobile robotic

systems make use of GPS to navigate. The robot will decide how it will get to

its destination and is able to detect a target and the rest of the surrounding

environment.

Obstacle Course

Mobile robotic platforms used in national security applications must move

within unstructured environments. The ability to operate over challenging

terrain and the ability to autonomously navigate in unstructured

environments are areas of focus, LaSelle points out. The migration of

automated systems from factory lines to moving freely throughout facilities

and beyond has created demands on system design

INDUSTRIES AND MININGENGINEERING


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Robots will be doing jobs like laying explosives, goingunderground afterblasting to stabilize a mine roof or mining in areas where it is impossible forhumans to work..Examples of the trend to mining automation include:Tele-operated and automated load-haul-dump trucks that self-navigate

through tunnels, clearing the walls by centimetersThe worlds largest robot, a 3500 tonne coal drag linefeaturing automatedloading and unloading.A robot device for drilling and bolting mine roofs to stabilize them afterblasting.A pilot less burrowing machine for mining in flooded g rave ls andsa nd s un de rg ro un d, wh er e hu ma n operators cannot go.A robotic drilling and blasting device for inducing controlled caving.Fig.1. Afew mining vehicle-related a

R o b o t i c technology offers significant potential to improve the difficulty of therescue workers by reducing exposures to hazardous conditions. A roboticvehicle can explore the mine and provide valuable information to theteams to assist in planning and implementing search and


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rescue operations. Industrial robots have been made a significant contributiontoward automating the manufacturing processes. The ef ficientuse of robots shows product iv ity increase, p r o d u c t i o n c o s tr e d u c t i o n , a n d p r o d u c t q u a l i t y improvement. However,

most robots currently in use perform simple repetitive jobs, such aspick-and-place, machine loading and unloading, spry painting andspot welding. A basic approach has been assumed for the testing of theperformance of the semi-autonomous robot. It has been seen that thisperforms well under the simple a s s u m p t i o n s o f t h e c o n d i t i o n se s t a b l i s h e d a t t h e underground mining excavation sites. Therecent fatality statistics for both underground as well as open cast miningoperations worldwide point out that the most serious risks to thepersonnel are from different mining condit ion especially that from theinaccessible areas of the mines where regular systematic monitoringand maintenance operations are difficult and hence, none of these operations

are not carried out on a systematic basis. It is true that there is nocontrol of the human operators on such unwanted happenings. Ingeneral, underground and opencast mining conditions are a cooperativeenterprise of powerful, mobile equipment and the workers who operate it. Ifmining equipment could be automated to function without a workers

full attention ,the mining industry could enhance productivity, accessunworkable mineral seams, and reduce human exposure to the inhospitableenvironment of dust, noise, gas, water, moving equipment and roof fall. Thecritical missing link to enable mine automation is the capability of equipment toestimate its position relative to its surrounding. The lack of accurate mapsof inactive, underground mines poses a serious threat to publicsafety. According to a recent study t ens o f t housands, perhapseven hundreds o f thousands, of abandoned mines exist today in theUnited States. Not even the U.S. Bureau of Mines knows the exact number,because federal recording of mining claims was not required until 1976.Hazardous operating conditions and difficult access routes suggest thatrobotic exploration and mapping of abandoned mines may be a viable option.

For maintain the working environment safety, it is now essential toimplemented robotic systems in underground

wireless controlled robotic car

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