Successfully reported this slideshow.

Vehicle tracking system using gps and gsm techniques



Loading in …3
1 of 88
1 of 88

More Related Content

Related Books

Free with a 14 day trial from Scribd

See all

Vehicle tracking system using gps and gsm techniques

  1. 1. A Major Project Report On Vehicle Tracking System using GSM and GPS Submitted in partial fulfillment of the requirement for the degree of BACHELOR OF TECHNOLOGY In ELECTRONICS & COMMUNICATION ENGINEERING Submitted by CH. Bharath. 107B1A0435 P. Vijay Kumar. 107B1A0437 P. Anil Reddy. 107B1A0449 B. Abhishek. 107B1A0468 Under the Esteemed Guidance of Mr. B. SRINIVAS M. Tech, MISTE, AMIE, (Ph.D) Assistant Professor DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING SAGAR INSTITUTE OF TECHNOLOGY (SITECH) SAGAR GROUP OF INSTITUTIONS (Affiliated to JNTU Hyderabad and Approved by AICTE, New Delhi) Flame of Forest, Urella-Chevella Road, Chevella, RR District (2010-2014)
  2. 2. Certificate This is to certify that this dissertation work entitled “Vehicle Tracking System using GSM and GPS” is a bonafide work carried out by CH. Bharath (107B1A0435), P. Vijay Kumar (107B1A0437), P. Anil Reddy (107B1A0449) and B. Abhishek (107B1A0468) in partial fulfillment of the requirements for the award of the degree of Bachelor of Technology in Electronics and Communication Engineering, from “Sagar Institute of Technology”, during the period 2013 under the guidance and supervision. Head of the Department Prof. V. BhagyaRaju M. Tech,(Ph.D.) Professor & HOD of ECE. Internal Guide Mr. B. SRINIVAS M. Tech, MISTE, AMIE, (Ph.D.) Assistant Professor Department of ECE External Examiner SAGAR GROUP OF INSTITUTINS SAGAR INSTITUTE OF TECHNOLOGY (Affiliated to JNTU Hyderabad and Approved by AICTE, New Delhi) Flame of Forest, Urella- Chevella Road, Chevella, RR Dist.
  3. 3. DECLARATION We hereby declare that the project “Vehicle Tracking System using GSM and GPS” submitted in the partial fulfilment of that requirements for the award of the degree of bachelor of technology in electronics and communication engineering from Sagar Institute Of Engineering and Technology, Chevella, affiliated to JNTU, Hyderabad is an authentic work and has not been submitted to any other university/institute for award of degree. CH. Bharath (107B1A0435) P. Vijay Kumar (107B1A0437) P. Anil Reddy (107B1A0449) B. Abhishek (107B1A0468) i
  4. 4. ACKNOWLEDGEMENT With great pleasure we want to take this opportunity to express our heartfelt gratitude to all the people who helped in making this Major Project work a grand success. We are grateful to Prof.V.Bhagya Raju, Professor & Head of Electronics and Communication Engineering department, Mr. B. Srinivas, Asst. Prof. Dept of ECE and P. Tejaswi Project Assistant at ECIL for their valuable suggestions and guidance during the execution of this project and also for giving us moral support throughout the period of our study in SITECH. We are also highly indebted to our principal Dr. V.V. Satyanarayana, for giving us the permission to carry out this Major Project. We would like to thank the teaching and non-teaching staff of ECE Department for sharing their knowledge with us. Last but not the least we express our sincere thanks to Dr.W.R.Reddy and all the founders of Sagar Institute of Technology for their continuous care towards our achievements. ii
  5. 5. Index Declaration i Acknowledgement ii Index iii List of Figures viii List of Tables ix Abbreviations x Chapter 1: Introduction To VTS 1 1.1 Introduction 1 1.2 Vehicle Security using VTS 2 1.3 Active versus Passive Tracking 4 1.4 Types of GPS Vehicle Tracking 5 1.5 Typical Architecture 6 1.6 History of Vehicle Tracking 7 1.6.1 Early Technology 8 1.6.2 New development in technology 9 1.7 Vehicle Tracking System Features 9 1.7.1 Vehicle Tracking Benefits 10 1.8 Vehicle Tracing in India 10 Chapter 2: Block Diagram of VTS 12 2.1 Block Diagram of Vehicle Tracing Using GSM and GPS Modem 2.2 Hardware Components 2.2.1 GPS 13 iii
  6. 6. Working of GPS 13 Triangulation 14 Augmentation 14 2.2.2 GSM 15 2.2.3 RS232 Interface 16 The scope of the standard 16 History of RS 232 17 Limitation of Standard 18 Standard details 19 Connectors 21 Cables 24 Conventions 24 RTS/CTS handshaking 25 3-wire and 5-wire RS-232 26 Seldom used features 26 Timing Signals 27 Other Serial interfaces similar to RS-232 27 2.2.4 MAX232 IC 28 Voltage Levels 29 Pin Diagram 30 Pin Description 31 2.2.5 Relay 31 History of a Relay 32 Basic Design and Operation of a Relay 33 iv
  7. 7. Pole and Throw 34 Uses of Relays 35 2.2.6 LCD 35 Advantages and Disadvantages 36 Chapter 3: Working of VTS 37 3.1 Schematic Diagram of VTS 37 3.2 Circuit Description 37 3.3 Circuit Operation 38 3.3.1 Power 38 3.3.2 Serial Ports 38 3.4 Operating procedure 38 Chapter 4: Microcontroller AT 89S52 40 4.1 Features 40 4.2 The Pin Configuration 41 4.2.1 Special Function Registers (SFR) 42 4.3 Memory Organization 43 4.4 Watch Dog Timer 43 4.4.1 Watchdog Timer for both modes of operation 44 Chapter 5: GSM Module 46 5.1 GSM History 46 5.2 Services Provided by GSM 47 5.3 Mobile Station 48 5.4 Base Station Subsystem 50 5.4.1 Base Station Controller 51 v
  8. 8. 5.5 Architecture of the GSM Network 52 5.6 Radio Link Aspects 53 5.7 Multiple Access and Channel Structure 54 5.8 Frequency Hopping 54 5.9 Discontinuous Reception 55 5.10 Power Control 55 5.11 Network Aspects 56 5.12 Radio Resources Management 57 5.13 Handover 57 5.14 Mobility Management 59 5.15 Location Updating 59 5.16 Authentication and Security 60 5.17 Communication Management 61 5.18 Call Routing 61 Chapter 6: GPS Receiver 63 6.1 GPS History 63 6.1.1 Working and Operation 64 6.2 GPS Data Decoding 65 Chapter 7: KEIL Software 67 7.1 Introduction 67 7.2 KEIL uVision2 66 7.3 KEIL Software Programing Procedure 67 7.3.1 Procedure Steps 67 7.4 Applications of KEIL Software 69 vi
  9. 9. Chapter 8: Applications 70 8.1 Applications 71 8.2 Limitations 72 Chapter 9: Result Analysis 73 Chapter 10: Conclusion and Future Scope 75 References 76 vii
  10. 10. List of Figures Figure 1.1 Vehicle tracking system 2 Figure 2.1 Block diagram 12 Figure 2.2 A 25 pin connector as described in the RS-232 standard 16 Figure 2.3 Trace of voltage levels for uppercase ASCII "K" character 19 Figure 2.4 Upper Picture: RS232 signaling as seen when probed by an actual oscilloscope 20 Figure 2.5 MAX232 chip 28 Figure 2.6 Pin diagram of MAX232 30 Figure 2.7 UK Q-style signaling relay and base. 32 Figure 2.8 Automotive-style miniature relay, dust cover is taken off 32 Figure 2.9 Circuit symbols of relays. 34 Figure 2.10 A general purpose alphanumeric LCD, with two lines of 16 characters. 35 Figure 3.1 Schematic diagram of vehicle tracing using GSM and GPS 37 Figure 5.1 Mobile station SIM port 49 Figure 5.2 Baste Station Subsystem. 50 Figure 5.3 Siemens BSC 51 Figure 5.4 Siemens’ TRAU 52 Figure 5.5 General architecture of a GSM network 53 Figure 5.6 Signaling protocol structure in GSM 57 Figure 5.7 Call routing for a mobile terminating call 61 Figure 6.1 G.P.S receiver communicating with the satellite 65 Figure 9.1 Picture of final VTS kit 73 Figure 9.2 Message received from the VTS kit 74 viii
  11. 11. List of Tables Table 2.1 Commonly used RS-232 signals and pin assignments 22 Table 2.2 Pin assignments 23 Table 2.3 RS-232 Voltage Levels 29 Table 2.4 TX and RX pin connection 30 Table 2.5 Pins assignment of MAX232 30 ix
  12. 12. Abbreviations VTS Vehicle Tracking System GSM Global System for Mobile Communication GPS Global Positioning System RI Ring Indicator Tx Transmitter Rx Receiver SFR Special Function Register LCD Liquid Crystal Display RAM Random Access Memory ROM Read Only Memory RS-232 Recommended Standard TTL Transistor Transistor Logic CMOS Complementary Metal Oxide Semi-Conductor UART Universal Asynchronous Receiver Transmitter RST Reset ALE Address Latch Enable PSEN Program Store Enable WDT Watch Dog Timer x
  13. 13. Chapter 1 Introduction to VTS 1.1 Introduction Vehicle Tracking System (VTS) is the technology used to determine the location of a vehicle using different methods like GPS and other radio navigation systems operating through satellites and ground based stations. By following triangulation or trilateration methods the tracking system enables to calculate easy and accurate location of the vehicle. Vehicle information like location details, speed, distance traveled etc. can be viewed on a digital mapping with the help of a software via Internet. Even data can be stored and downloaded to a computer from the GPS unit at a base station and that can later be used for analysis. This system is an important tool for tracking each vehicle at a given period of time and now it is becoming increasingly popular for people having expensive cars and hence as a theft prevention and retrieval device. i. The system consists of modern hardware and software components enabling one to track their vehicle online or offline. Any vehicle tracking system consists of mainly three parts mobile vehicle unit, fixed based station and, database and software system. ii. Vehicle Unit: It is the hardware component attached to the vehicle having either a GPS/GSM modem. The unit is configured around a primary modem that functions with the tracking software by receiving signals from GPS satellites or radio station points with the help of antenna. The controller modem converts the data and sends the vehicle location data to the server. iii. Fixed Based Station: Consists of a wireless network to receive and forward the data to the data center. Base stations are equipped with tracking software and geographic map useful for determining the vehicle location. Maps of every city and landmarks are available in the based station that has an in-built Web Server. iv. Database and Software: The position information or the coordinates of each visiting points are stored in a database, which later can be viewed in a display screen using digital maps. However, the users have to connect themselves to the web server with the respective vehicle ID stored in the database and only then s/he can view the location of vehicle traveled. 1
  14. 14. 1.2 Vehicle Security using VTS Vehicle Security is a primary concern for all vehicle owners. Owners as well as researchers are always on the lookout for new and improved security systems for their vehicles. One has to be thankful for the upcoming technologies, like GPS systems, which enables the owner to closely monitor and track his vehicle in real-time and also check the history of vehicles movements. This new technology, popularly called Vehicle Tracking Systems has done wonders in maintaining the security of the vehicle tracking system is one of the biggest technological advancements to track the activities of the vehicle. The security system uses Global Positioning System GPS, to find the location of the monitored or tracked vehicle and then uses satellite or radio systems to send to send the coordinates and the location data to the monitoring center. At monitoring center various software’s are used to plot the Vehicle on a map. In this way the Vehicle owners are able to track their vehicle on a real-time basis. Due to real-time tracking facility, vehicle tracking systems are becoming increasingly popular among owners of expensive vehicles. Figure 1.1 Vehicle tracking system The vehicle tracking hardware is fitted on to the vehicle. It is fitted in such a manner that it is not visible to anyone who is outside the vehicle. Thus it operates as a covert unit which continuously sends the location data to the monitoring unit. When the vehicle is stolen, the location data sent by tracking unit can be used to find the location and coordinates can be sent to police for further action. Some Vehicle tracking System can even detect unauthorized movements of the vehicle and then alert the owner. This gives an edge over other pieces of technology for the same purpose Monitoring center Software helps the vehicle owner with a view of the location at which the vehicle stands. Browsing is easy and the owners can make use of any browser and connect to the monitoring center software, to find and track his vehicle. This 2
  15. 15. in turn saves a lot of effort to find the vehicle's position by replacing the manual call to the driver. As we have seen the vehicle tracking system is an exciting piece of technology for vehicle security. It enables the owner to virtually keep an eye on his vehicle any time and from anywhere in the world. A vehicle tracking system combines the installation of an electronic device in a vehicle, or fleet of vehicles, with purpose-designed computer software at least at one operational base to enable the owner or a third party to track the vehicle's location, collecting data in the process from the field and deliver it to the base of operation. Modern vehicle tracking systems commonly use GPS or GLONASS technology for locating the vehicle, but other types of automatic vehicle location technology can also be used. Vehicle information can be viewed on electronic maps via the Internet or specialized software. Urban public transit authorities are an increasingly common user of vehicle tracking systems, particularly in large cities. Vehicle tracking systems are commonly used by fleet operators for fleet management functions such as fleet tracking, routing, dispatch, on-board information and security. Along with commercial fleet operators, urban transit agencies use the technology for a number of purposes, including monitoring schedule adherence of buses in service, triggering changes of buses' destination sign displays at the end of the line (or other set location along a bus route), and triggering pre-recorded announcements for passengers. The American Public Transportation Association estimated that, at the beginning of 2009, around half of all transit buses in the United States were already using a GPS-based vehicle tracking system to trigger automated stop announcements. This can refer to external announcements (triggered by the opening of the bus's door) at a bus stop, announcing the vehicle's route number and destination, primarily for the benefit of visually impaired customers, or to internal announcements (to passengers already on board) identifying the next stop, as the bus (or tram) approaches a stop, or both. Data collected as a transit vehicle follows its route is often continuously fed into a computer program which compares the vehicle's actual location and time with its schedule, and in turn produces a frequently updating display for the driver, telling him/her how early or late he/she is at any given time, potentially making it easier to adhere more closely to the published schedule. Such programs are also used to provide customers with real-time information as to the waiting time until arrival of the next bus or tram/streetcar at a given stop, based on the nearest vehicles' actual progress at the time, rather than merely giving 3
  16. 16. information as to the scheduled time of the next arrival. Transit systems providing this kind of information assign a unique number to each stop, and waiting passengers can obtain information by entering the stop number into an automated telephone system or an application on the transit system's website. Some transit agencies provide a virtual map on their website, with icons depicting the current locations of buses in service on each route, for customers' information, while others provide such information only to dispatchers or other employees. Other applications include monitoring driving behavior, such as an employer of an employee, or a parent with a teen driver. Vehicle tracking systems are also popular in consumer vehicles as a theft prevention and retrieval device. Police can simply follow the signal emitted by the tracking system and locate the stolen vehicle. When used as a security system, a Vehicle Tracking System may serve as either an addition to or replacement for a traditional car alarm. Some vehicle tracking systems make it possible to control vehicle remotely, including block doors or engine in case of emergency. The existence of vehicle tracking device then can be used to reduce the insurance cost, because the loss-risk of the vehicle drops significantly. Vehicle tracking systems are an integrated part of the "layered approach" to vehicle protection, recommended by the National Insurance Crime Bureau (NICB) to prevent motor vehicle theft. This approach recommends four layers of security based on the risk factors pertaining to a specific vehicle. Vehicle Tracking Systems are one such layer, and are described by the NICB as “very effective” in helping police recover stolen vehicles. Some vehicle tracking systems integrate several security systems, for example by sending an automatic alert to a phone or email if an alarm is triggered or the vehicle is moved without authorization, or when it leaves or enters a geofence. 1.3 Active versus Passive Tracking Several types of vehicle tracking devices exist. Typically they are classified as "passive" and "active". "Passive" devices store GPS location, speed, heading and sometimes a trigger event such as key on/off, door open/closed. Once the vehicle returns to a predetermined point, the device is removed and the data downloaded to a computer for evaluation. Passive systems include auto download type that transfer data via wireless download. "Active" devices also collect the same information but usually transmit the 4
  17. 17. data in real-time via cellular or satellite networks to a computer or data center for evaluation. Many modern vehicle tracking devices combine both active and passive tracking abilities: when a cellular network is available and a tracking device is connected it transmits data to a server; when a network is not available the device stores data in internal memory and will transmit stored data to the server later when the network becomes available again. Historically vehicle tracking has been accomplished by installing a box into the vehicle, either self-powered with a battery or wired into the vehicle's power system. For detailed vehicle locating and tracking this is still the predominant method; however, many companies are increasingly interested in the emerging cell phone technologies that provide tracking of multiple entities, such as both a salesperson and their vehicle. These systems also offer tracking of calls, texts, and Web use and generally provide a wider range of options. 1.4 Types of GPS Vehicle Tracking There are three main types of GPS vehicle tracking, tracking based mobile, wireless passive tracking and satellite in real-time GPS tracking. This article discusses the advantages and disadvantages to all three types of GPS vehicle tracking circumference. i) Mobile phone based tracking The initial cost for the construction of the system is slightly lower than the other two options. With a mobile phone-based tracking average price is about $ 500. A cell- based monitoring system sends information about when a vehicle is every five minutes during a rural network. The average monthly cost is about thirty-five dollars for airtime. ii) Wireless Passive Tracking A big advantage that this type of tracking system is that there is no monthly fee, so that when the system was introduced, there will be other costs associated with it. But setting the scheme is a bit 'expensive. The average is about $ 700 for hardware and $ 800 for software and databases. With this type of system, most say that the disadvantage is that information about where the vehicle is not only can exist when the vehicle is returned to the base business. This is a great disadvantage, particularly for companies that are looking for a monitoring system that tells them where their vehicle will be in case of theft or an accident. However, many systems are now introducing wireless modems into their 5
  18. 18. devices so that tracking information can be without memory of the vehicle to be seen. With a wireless modem that is wireless passive tracking systems are also able to gather information on how fast the vehicle was traveling, stopping, and made other detailed information. With this new addition, many companies believe that this system is perfect, because there is no monthly bill. iii) Via satellite in real time This type of system provides less detailed information, but work at the national level, making it a good choice for shipping and trucking companies. Spending on construction of the system on average about $ 700. The monthly fees for this system vary from five dollars for a hundred dollars, depending on how the implementation of a reporting entity would be. Technology Over the next few years, GPS tracking will be able to provide businesses with a number of other benefits. Some companies have already introduced a way for a customer has signed the credit card and managed at local level through the device. Others are creating ways for dispatcher to send the information re-routing, the GPS device directly to a manager. Not a new requirement for GPS systems is that they will have access to the Internet and store information about the vehicle as a driver or mechanic GPS device to see the diagrams used to assist with the vehicle you want to leave. Beyond that all the information be saved and stored in its database. 1.5 Typical Architecture Major constituents of the GPS based tracking are i. GPS tracking device The device fits into the vehicle and captures the GPS location information apart from other vehicle information at regular intervals to a central server. The other vehicle information can include fuel amount, engine temperature, altitude, reverse geocoding, door open/close, tire pressure, cut off fuel, turn off ignition, turn on headlight, turn on taillight, battery status, GSM area code/cell code decoded, number of GPS satellites in view, glass open/close, fuel amount, emergency button status, cumulative idling, computed odometer, engine RPM, throttle position, and a lot more. Capability of these devices actually decides the final capability of the whole tracking system. 6
  19. 19. ii. GPS tracking server The tracking server has three responsibilities: receiving data from the GPS tracking unit, securely storing it, and serving this information on demand to the user. iii. User interface The UI determines how one will be able to access information, view vehicle data, and elicit important details from it. 1.6 History of Vehicle Tracking GPS or Global Positioning Systems were designed by the United States Government and military, which the design was intended to be used as surveillance. After several years went by the government signed a treaty to allow civilians to buy GPS units also only the civilians would get precise downgraded ratings. Years after the Global Positioning Systems were developed the military controlled the systems despite that civilians could still purchase them in stores. In addition, despite that Europe has designed its own systems called the Galileo the US military still has complete control. GPS units are also called tracking devices that are quite costly still. As more of these devices develop however the more affordable the GPS can be purchased. Despite of the innovative technology and designs of the GPS today the devices has seen some notable changes or reductions in pricing. Companies now have more access to these devices and many of the companies can find benefits. These days you can pay-as-you go or lease a GPS system for your company. This means you do not have to worry about spending upfront money, which once stopped companies from installing the Global positioning systems at one time. Today’s GPS applications have vastly developed as well. It is possible to use the Global Positioning Systems to design expense reports, create time sheets, or reduce the costs of fuel consumption. You can also use the tracking devices to increase efficiency of employee driving. The GPS unit allows you to create Geo-Fences about a designated location, which gives you alerts once your driver(s) passes through. This means you have added security combined with more powerful customer support for your workers. Today’s GPS units are great tracking devices that help fleet managers stay in control of their business. The applications in today’s GPS units make it possible to take full 7
  20. 20. control of your company. It is clear that the tracking devices offer many benefits to companies, since you can build automated expense reports anytime. GPS units do more than just allow companies to create reports. These devices also help to put an end to thieves. According to recent reports, crime is at a high, which means that car theft is increasing. If you have the right GPS unit, you can put an end to car thefts because you can lock and unlock your car anytime you choose. GPS are small tracking devices that are installed in your car and it will supply you with feedback data from tracking software that loads from a satellite. This gives you more control over your vehicles. The chief reason for companies to install tracking devices is to monitor their mobile workforce. A preventive measure device allows companies to monitor their employees’ activities. Company workers can no longer take your vehicles to unassigned locations. They will not be able to get away with unauthorized activities at any time because you can monitor their every action on a digital screen. The phantom pixel is another thing some webmasters do to get better rankings. Unfortunately it will backfire on you since the search engines do not want this to occur. You see, the phantom pixel is when you might have a 1 pixel image or an image so small it cannot be seen by the regular eye. They use the pixel to stuff it with keywords. The search engine can view it in the code, which is how they know it is there and can give you better rank for the keywords in theory. Of course since the search engines don’t like this phantom pixel you are instead not getting anything for the extra keywords except sent to the bottomless pit. 1.6.1 Early Technology In the initial period of tracking only two radios were used to exchange the information. One radio was attached to the vehicle while another at base station by which drivers were enabled to talk to their masters. Fleet operator could identify the progress through their routes. The technology was not without its limits. It was restricted by the distance which became a hurdle in accuracy and better connectivity between driver and fleet operators. Base station was dependent on the driver for the information and a huge size fleet could not have been managed depending on man-power only. The scene of vehicle tracking underwent a change with the arrival of GPS technology. This reduced the dependence on man-power. Most of the work of tracking 8
  21. 21. became electronic. Computers proved a great help in managing a large fleet of vehicle. This also made the information authentic. As this technology was available at affordable cost all whether small or big fleet could take benefit of this technology Because of the cheap accessibility of the device computer tracking facilities has come to stay and associated with enhanced management. Today each vehicle carries tracking unit which is monitored from the base station. Base station receives the data from the unit. All these facilities require a heavy investment of capital for the installation of the infrastructure of tracking system for monitoring and dispatching 1.6.2 New development in technology New system costs less with increased efficiency. Presently it is small tracking unit in the vehicle with web-based interface, connected through a mobile phone. This device avoids unnecessary investment in infrastructure with the facility of monitoring from anywhere for the fleet managers. This provides more efficient route plan to fleet operators of all sizes and compositions saving money and time. Vehicle tracking system heralded a new era of convenience and affordability in fleet management. Thus due to its easy availability it is going to stay for long. 1.7 Vehicle Tracking System Features Monitoring and managing the mobile assets are very important for any company dealing with the services, delivery or transport vehicles. Information technologies help in supporting these functionalities from remote locations and update the managers with the latest information of their mobile assets. Tracking the mobile assets locations data and analyzing the information is necessary for optimal utilization of the assets. Vehicle Tracking System is a software & hardware system enabling the vehicle owner to track the position of their vehicle. A vehicle tracking system uses either GPS or radio technology to automatically track and record a fleet's field activities. Activity is recorded by modules attached to each vehicle. And then the data is transmitted to a central, internet-connected computer where it is stored. Once the data is transmitted to the computer, it can be analyzed and reports can be downloaded in real-time to your computer using either web browser based tools or customized software. 9
  22. 22. 1.7.1 Vehicle Tracking Benefits An enterprise-level vehicle tracking system should offer customizable reporting tools, for example to provide a summary of the any day activities. It should have the ability to produce and print detailed maps and reports displaying actual stops, customer locations, mileage traveled, and elapsed time at each location, and real-time access to vehicle tracking data and reports. Vehicle tracking system can be active, passive or both depending upon the application. Here are steps involved in the vehicle tracking: i. Data capture: Data capturing is the first step in tacking your vehicle. Data in a vehicle tracking system is captured through a unit called automated vehicle unit. The automated vehicle unit uses the Global Positioning System (GPS) to determine the location of the vehicle. This unit is installed in the vehicle and contains interfaces to various data sources. This paper considers the location data capture along with data from various sensors like fuel, vehicle diagnostic sensors etc. ii. Data storage: Captured data is stored in the memory of the automated vehicle unit. iii. Data transfer: Stored data are transferred to the computer server using the mobile network or by connecting the vehicle mount unit to the computer. iv. Data analysis: Data analysis is done through software application. A GIS mapping component is also an integral part of the vehicle tracking system and it is used to display the correct location of the vehicle on the map. 1.8 Vehicle Tracing in India Vehicle tracking system in India is mainly used in transport industry that keeps a real-time track of all vehicles in the fleet. The tracking system consists of GPS device that brings together GPS and GSM technology using tracking software. The attached GPS unit in the vehicle sends periodic updates of its location to the route station through the server of the cellular network that can be displayed on a digital map. The location details are later transferred to users via SMS, e-mail or other form of data transfers. There are various GPS software and hardware developing companies in India working for tracking solutions. However, its application is not that much of popular as in other countries like USA, which regulates the whole GPS network. In India it is mostly used in Indian transport and logistics industry and not much personal vehicle tracking. 10
  23. 23. But with better awareness and promotion the market will increase. Let’s have a look at its current application in India using vehicle tracking though in less volume. a) Freight forwarding Logistic service providers are now increasingly adopting vehicle-tracking system for better fleet management and timely service. The system can continuously monitor shipment location and so can direct the drivers directly in case of any change of plan. Fleet managers can keep an eye on all activities of workers, vehicle over speed, route deviation etc. The driver in turn can access emergency service in case of sickness, accident or vehicle breakdown. All in turn supports money and time management, resulting better customer service. b) Call centers In commercial vehicle segments the taxi operators of various call centers are now using vehicle tracking system for better information access. However, its application is in its infant stage in India and if adequate steps are taken in bringing the cost of hardware and software low then it can be used for tracking personal vehicle, farming (tractor), tourist buses, security and emergency vehicle etc. Again Government needs to cut down the restriction imposed upon the availability of digital maps for commercial use and this will encourage software industry in developing cost-effective tracking solutions. Though, sales of both commercial and passenger vehicles are growing but price of tracking service is very high and this is the key issue in Indian market. Hence, it’s important for market participants to reduce prices of GPS chips and other products in order to attract more and more users. As far as Indian vehicle tracking and navigation market is concerned the recent association of India with Russian Global Navigation Satellite System (GLONASS) will act as a catalyst in the improvement of vehicle tracking system. This will give an advantage in managing traffic, roadways and ports and also as an important tool for police and security agency to track stolen vehicles. Hence, in near future there is large prospect for the utility of vehicle tracking system in India, which can revolutionize the way we are communicating. 11
  24. 24. Chapter 2 Block Diagram of VTS 2.1 Block Diagram of Vehicle Tracing Using GSM and GPS Modem Figure 2.1 Block diagram 2.2 Hardware Components  AT89S52  GPS MODULE  GSM MODULE  RS232  MAX 232  RELAY  LCD In this project AT89S52 microcontroller is used for interfacing to various hardware peripherals. The current design is an embedded application, which will continuously monitor a moving Vehicle and report the status of the Vehicle on demand. For doing so an AT89S52 microcontroller is interfaced serially to a GSM Modem and GPS Receiver. A GSM modem is used to send the position (Latitude and Longitude) of the vehicle from a remote place. The GPS modem will continuously give the data i.e. the latitude and longitude indicating the position of the vehicle. The GPS modem gives many parameters as the output, but only the NMEA data coming out is read and displayed on to the LCD. The same data is sent to the mobile at the other end from where the position of the vehicle is demanded. An EEPROM is used to store the mobile number. The hardware interfaces to microcontroller are LCD display, GSM modem and GPS Receiver. The design uses RS-232 protocol for serial communication between the modems and the microcontroller. A serial driver IC is used for converting TTL voltage 12
  25. 25. levels to RS-232 voltage levels. When the request by user is sent to the number at the modem, the system automatically sends a return reply to that mobile indicating the position of the vehicle in terms of latitude and longitude. As the Micro Controller, GPS and GSM take a sight of in depth knowledge, they are explained in the next chapters. 2.2.1 GPS GPS, in full Global Positioning System, space-based radio-navigation system that broadcasts highly accurate navigation pulses to users on or near the Earth. In the United States’ Navstar GPS, 24 main satellites in 6 orbits circle the Earth every 12 hours. In addition, Russia maintains a constellation called GLONASS (Global Navigation Satellite System). Working of GPS GPS receiver works on 9600 baud rate is used to receive the data from space Segment (from Satellites), the GPS values of different Satellites are sent to microcontroller AT89S52, where these are processed and forwarded to GSM. At the time of processing GPS receives only $GPRMC values only. From these values microcontroller takes only latitude and longitude values excluding time, altitude, name of the satellite, authentication etc. E.g. LAT: 1728:2470 LOG: 7843.3089 GSM modem with a baud rate 57600. A GPS receiver operated by a user on Earth measures the time it takes radio signals to travel from four or more satellites to its location, calculates the distance to each satellite, and from this calculation determines the user’s longitude, latitude, and altitude. The U.S. Department of Defense originally developed the Navstar constellation for military use, but a less precise form of the service is available free of charge to civilian users around the globe. The basic civilian service will locate a receiver within 10 meters (33 feet) of its true location, though various augmentation techniques can be used to pinpoint the location within less than 1 cm (0.4 inch). With such accuracy and the ubiquity of the service, GPS has evolved far beyond its original military purpose and has created a revolution in personal and commercial navigation. Battlefield missiles and artillery projectiles use GPS signals to determine their positions and velocities, but so do the U.S. space shuttle and the International Space Station as well as commercial jetliners and private airplanes. Ambulance fleets, family automobiles, and railroad locomotives 13
  26. 26. benefit from GPS positioning, which also serves farm tractors, ocean liners, hikers, and even golfers. Many GPS receivers are no larger than a pocket calculator and are powered by disposable batteries, while GPS computer chips the size of a baby’s fingernail have been installed in wristwatches, cellular telephones, and personal digital assistants. Triangulation The principle behind the unprecedented navigational capabilities of GPS is triangulation. To triangulate, a GPS receiver precisely measures the time it takes for a satellite signal to make its brief journey to Earth—less than a tenth of a second. Then it multiplies that time by the speed of a radio wave—300,000 km (186,000 miles) per second—to obtain the corresponding distance between it and the satellite. This puts the receiver somewhere on the surface of an imaginary sphere with a radius equal to its distance from the satellite. When signals from three other satellites are similarly processed, the receiver’s built-in computer calculates the point at which all four spheres intersect, effectively determining the user’s current longitude, latitude, and altitude. (In theory, three satellites would normally provide an unambiguous three-dimensional fix, but in practice at least four are used to offset inaccuracy in the receiver’s clock.) In addition, the receiver calculates current velocity (speed and direction) by measuring the instantaneous Doppler effect shifts created by the combined motion of the same four satellites. Augmentation Although the travel time of a satellite signal to Earth is only a fraction of a second, much can happen to it in that interval. For example, electrically charged particles in the ionosphere and density variations in the troposphere may act to slow and distort satellite signals. These influences can translate into positional errors for GPS users—a problem that can be compounded by timing errors in GPS receiver clocks. Further errors may be introduced by relativistic time dilations, a phenomenon in which a satellite’s clock and a receiver’s clock, located in different gravitational fields and traveling at different velocities, tick at different rates. Finally, the single greatest source of error to users of the Navstar system is the lower accuracy of the civilian C/A-code pulse. However, various augmentation methods exist for improving the accuracy of both the military and the civilian systems. 14
  27. 27. When positional information is required with pinpoint precision, users can take advantage of differential GPS techniques. Differential navigation employs a stationary “base station” that sits at a known position on the ground and continuously monitors the signals being broadcast by GPS satellites in its view. It then computes and broadcasts real-time navigation corrections to nearby roving receivers. Each roving receiver, in effect, subtracts its position solution from the base station’s solution, thus eliminating any statistical errors common to the two. The U.S. Coast Guard maintains a network of such base stations and transmits corrections over radio beacons covering most of the United States. Other differential corrections are encoded within the normal broadcasts of commercial radio stations. Farmers receiving these broadcasts have been able to direct their field equipment with great accuracy, making precision farming a common term in agriculture. Another GPS augmentation technique uses the carrier waves that convey the satellites’ navigation pulses to Earth. Because the length of the carrier wave is more than 1,000 times shorter than the basic navigation pulses, this “carrier-aided” approach, under the right circumstances, can reduce navigation errors to less than 1 cm (0.4 inch). The dramatically improved accuracy stems primarily from the shorter length and much greater numbers of carrier waves impinging on the receiver’s antenna each second. Yet another augmentation technique is known as geosynchronous overlays. Geosynchronous overlays employ GPS payloads “piggybacked” aboard commercial communication satellites that are placed in geostationary orbit some 35,000 km (22,000 miles) above the Earth. These relatively small payloads broadcast civilian C/A-code pulse trains to ground-based users. The U.S. government is enlarging the Navstar constellation with geosynchronous overlays to achieve improved coverage, accuracy, and survivability. Both the European Union and Japan are installing their own geosynchronous overlays. 2.2.2 GSM GSM (or Global System for Mobile Communications) was developed in 1990. The first GSM operator has subscribers in 1991, the beginning of 1994 the network based on the standard, already had 1.3 million subscribers, and the end of 1995 their number had increased to 10 million! There were first generation mobile phones in the 70's, there are 2nd generation mobile phones in the 80's and 90's, and now there are 3rd gen phones which are about to 15
  28. 28. enter the Indian market. GSM is called a 2nd generation, or 2G communications technology. In this project it acts as a SMS Receiver and SMS sender. The GSM technical specifications define the different entities that form the GSM network by defining their functions and interface requirements. 2.2.3 RS232 Interface In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pin out of connectors. The current version of the standard is TIA-232-F Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. An RS-232 port was once a standard feature of a personal computer for connections to modems, printers, mice, data storage, un-interruptible power supplies, and other peripheral devices. However, the limited transmission speed, relatively large voltage swing, and large standard connectors motivated development of the universal serial bus which has displaced RS-232 from most of its peripheral interface roles. Many modern personal computers have no RS-232 ports and must use an external converter to connect to older peripherals. Some RS-232 devices are still found especially in industrial machines or scientific instruments. Figure 2.2: 25 pin connector as described in the RS-232 standard The scope of the standard The Electronic Industries Association (EIA) standard RS-232-C[1] as of 1969 defines:  Electrical signal characteristics such as voltage levels, signaling rate, timing and slew-rate of signals, voltage withstand level, short-circuit behavior, and maximum load capacitance.  Interface mechanical characteristics, pluggable connectors and pin identification. 16
  29. 29.  Functions of each circuit in the interface connector.  Standard subsets of interface circuits for selected telecom applications. The standard does not define such elements as the character encoding or the framing of characters, or error detection protocols. The standard does not define bit rates for transmission, except that it says it is intended for bit rates lower than 20,000 bits per second. Many modern devices support speeds of 115,200 bit/s and above. RS 232 makes no provision for power to peripheral devices. Details of character format and transmission bit rate are controlled by the serial port hardware, often a single integrated circuit called a UART that converts data from parallel to asynchronous start-stop serial form. Details of voltage levels, slew rate, and short-circuit behavior are typically controlled by a line driver that converts from the UART's logic levels to RS-232 compatible signal levels, and a receiver that converts from RS-232 compatible signal levels to the UART's logic levels. History of RS 232 RS-232 was first introduced in 1962. The original DTEs were electromechanical teletypewriters, and the original DCEs were (usually) modems. When electronic terminals (smart and dumb) began to be used, they were often designed to be interchangeable with teletypewriters, and so supported RS-232. The C revision of the standard was issued in 1969 in part to accommodate the electrical characteristics of these devices. Since application to devices such as computers, printers, test instruments, and so on was not considered by the standard, designers implementing an RS-232 compatible interface on their equipment often interpreted the requirements idiosyncratically. Common problems were non-standard pin assignment of circuits on connectors, and incorrect or missing control signals. The lack of adherence to the standards produced a thriving industry of breakout boxes, patch boxes, test equipment, books, and other aids for the connection of disparate equipment. A common deviation from the standard was to drive the signals at a reduced voltage. Some manufacturers therefore built transmitters that supplied +5 V and -5 V and labeled them as "RS-232 compatible". Later personal computers (and other devices) started to make use of the standard so that they could connect to existing equipment. For many years, an RS-232-compatible port was a standard feature for serial communications, such as modem connections, on 17
  30. 30. many computers. It remained in widespread use into the late 1990s. In personal computer peripherals, it has largely been supplanted by other interface standards, such as USB. RS- 232 is still used to connect older designs of peripherals, industrial equipment (such as PLCs), console ports, and special purpose equipment, such as a cash drawer for a cash register. The standard has been renamed several times during its history as the sponsoring organization changed its name, and has been variously known as EIA RS-232, EIA 232, and most recently as TIA 232. The standard continued to be revised and updated by the Electronic Industries Alliance and since 1988 by the Telecommunications Industry Association (TIA).[3] Revision C was issued in a document dated August 1969. Revision D was issued in 1986. The current revision is TIA-232-F Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. Changes since Revision C have been in timing and details intended to improve harmonization with the CCITT standard V.24, but equipment built to the current standard will interoperate with older versions. Related ITU-T standards include V.24 (circuit identification) and V.28 (signal voltage and timing characteristics). Limitation of Standard Because the application of RS-232 has extended far beyond the original purpose of interconnecting a terminal with a modem, successor standards have been developed to address the limitations. Issues with the RS-232 standard include:  The large voltage swings and requirement for positive and negative supplies increases power consumption of the interface and complicates power supply design. The voltage swing requirement also limits the upper speed of a compatible interface.  Single-ended signaling referred to a common signal ground limits the noise immunity and transmission distance.  Multi-drop connection among more than two devices is not defined. While multi- drop "work-arounds" have been devised, they have limitations in speed and compatibility.  Asymmetrical definitions of the two ends of the link make the assignment of the role of a newly developed device problematic; the designer must decide on either a DTE-like or DCE-like interface and which connector pin assignments to use. 18
  31. 31.  The handshaking and control lines of the interface are intended for the setup and takedown of a dial-up communication circuit; in particular, the use of handshake lines for flow control is not reliably implemented in many devices.  No method is specified for sending power to a device. While a small amount of current can be extracted from the DTR and RTS lines, this is only suitable for low power devices such as mice.  The 25-way connector recommended in the standard is large compared to current practice. Standard details In RS-232, user data is sent as a time-series of bits. Both synchronous and asynchronous transmissions are supported by the standard. In addition to the data circuits, the standard defines a number of control circuits used to manage the connection between the DTE and DCE. Each data or control circuit only operates in one direction, that is, signaling from a DTE to the attached DCE or the reverse. Since transmit data and receive data are separate circuits, the interface can operate in a full duplex manner, supporting concurrent data flow in both directions. The standard does not define character framing within the data stream, or character encoding. Voltage levels Figure 2.3 Diagrammatic oscilloscope trace of voltage levels for an uppercase ASCII "K" character (0x4b) with 1 start bit, 8 data bits, 1 stop bit. This is typical for start-stop communications, but the standard does not dictate a character format or bit order. The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are plus or minus 3 to 15 volts; the ±3 V range near zero volts is not a valid RS-232 level. 19
  32. 32. Figure 2.4 Upper Picture: RS232 signaling as seen when probed by an actual oscilloscope (Tektronix MSO4104B) for an uppercase ASCII "K" character (0x4b) with 1 start bit (always), 8 data bits, 1 stop bit and no parity bits (8N1) The standard specifies a maximum open-circuit voltage of 25 volts: signal levels of ±5 V, ±10 V, ±12 V, and ±15 V are all commonly seen depending on the power supplies available within a device. RS-232 drivers and receivers must be able to withstand indefinite short circuit to ground or to any voltage level up to ±25 volts. The slew rate, or how fast the signal changes between levels, is also controlled. For data transmission lines (TxD, RxD and their secondary channel equivalents) logic one is defined as a negative voltage, the signal condition is called marking, and has the functional significance. Logic zero is positive and the signal condition is termed spacing. Control signals are logically inverted with respect to what one sees on the data transmission lines. When one of these signals is active, the voltage on the line will be between +3 to +15 volts. The inactive state for these signals is the opposite voltage condition, between −3 and −15 volts. Examples of control lines include request to send (RTS), clear to send (CTS), data terminal ready (DTR), and data set ready (DSR). Because the voltage levels are higher than logic levels typically used by integrated circuits, special intervening driver circuits are required to translate logic levels. These also protect the device's internal circuitry from short circuits or transients that may appear on the RS-232 interface, and provide sufficient current to comply with the slew rate requirements for data transmission. Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on 20
  33. 33. separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential, serial connections such as USB, RS-422 and RS-485 can tolerate larger ground voltage differences because of the differential signaling. Unused interface signals terminated to ground will have an undefined logic state. Where it is necessary to permanently set a control signal to a defined state, it must be connected to a voltage source that asserts the logic 1 or logic 0 level. Some devices provide test voltages on their interface connectors for this purpose. Connectors RS-232 devices may be classified as Data Terminal Equipment (DTE) or Data Communication Equipment (DCE); this defines at each device which wires will be sending and receiving each signal. The standard recommended but did not make mandatory the D-subminiature 25 pin connector. In general and according to the standard, terminals and computers have male connectors with DTE pin functions, and modems have female connectors with DCE pin functions. Other devices may have any combination of connector gender and pin definitions. Many terminals were manufactured with female terminals but were sold with a cable with male connectors at each end; the terminal with its cable satisfied the recommendations in the standard. Presence of a 25 pin D-sub connector does not necessarily indicate an RS-232-C compliant interface. For example, on the original IBM PC, a male D-sub was an RS-232- C DTE port (with a non-standard current loop interface on reserved pins), but the female D-sub connector was used for a parallel Centronics printer port. Some personal computers put non-standard voltages or signals on some pins of their serial ports.The standard specifies 20 different signal connections. Since most devices use only a few signals, smaller connectors can often be used. The following table lists commonly used RS-232 signals and pin assignments. The signals are named from the standpoint of the DTE. The ground signal is a common return for the other connections. The DB-25 connector includes a second "protective ground" on pin 1. Data can be sent over a secondary channel (when implemented by the DTE and DCE devices), which is equivalent to the primary channel. Pin assignments are described in shown in Table 2.2: 21
  34. 34. Table 2.1. Commonly used RS-232 signals and pin assignments Signal Origin DB-25 pin Name Typical purpose Abbreviation DTE DCE Data Terminal Ready Indicates presence of DTE to DCE. DTR ● 20 Data Carrier Detect DCE is connected to the telephone line. DCD ● 8 Data Set Ready DCE is ready to receive commands or data. DSR ● 6 Ring Indicator DCE has detected an incoming ring signal on the telephone line. RI ● 22 Request To Send DTE requests the DCE prepare to receive data. RTS ● 4 Clear To Send Indicates DCE is ready to accept data. CTS ● 5 Transmitted Data Carries data from DTE to DCE. TxD ● 2 Received Data Carries data from DCE to DTE. RxD ● 3 Common Ground GND common 7 Protective Ground PG common 1 22
  35. 35. Table 2.2 Pin assignments Signal Pin Common Ground 7 (same as primary) Secondary Transmitted Data (STD) 14 Secondary Received Data (SRD) 16 Secondary Request To Send (SRTS) 19 Secondary Clear To Send (SCTS) 13 Secondary Carrier Detect (SDCD) 12 Ring Indicator' (RI), is a signal sent from the modem to the terminal device. It indicates to the terminal device that the phone line is ringing. In many computer serial ports, a hardware interrupt is generated when the RI signal changes state. Having support for this hardware interrupt means that a program or operating system can be informed of a change in state of the RI pin, without requiring the software to constantly "poll" the state of the pin. RI is a one-way signal from the modem to the terminal (or more generally, the DCE to the DTE) that does not correspond to another signal that carries similar information the opposite way. On an external modem the status of the Ring Indicator pin is often coupled to the "AA" (auto answer) light, which flashes if the RI signal has detected a ring. The asserted RI signal follows the ringing pattern closely, which can permit software to detect distinctive ring patterns. The Ring Indicator signal is used by some older uninterruptible power supplies (UPS's) to signal a power failure state to the computer. Certain personal computers can be configured for wake-on-ring, allowing a computer that is suspended to answer a phone call. Cables The standard does not define a maximum cable length but instead defines the maximum capacitance that a compliant drive circuit must tolerate. A widely used rule of thumb indicates that cables more than 50 feet (15 m) long will have too much capacitance, unless special cables are used. By using low-capacitance cables, full speed 23
  36. 36. communication can be maintained over larger distances up to about 1,000 feet (300 m).[8] For longer distances, other signal standards are better suited to maintain high speed. Since the standard definitions are not always correctly applied, it is often necessary to consult documentation, test connections with a breakout box, or use trial and error to find a cable that works when interconnecting two devices. Connecting a fully standard- compliant DCE device and DTE device would use a cable that connects identical pin numbers in each connector (a so-called "straight cable"). "Gender changers" are available to solve gender mismatches between cables and connectors. Connecting devices with different types of connectors requires a cable that connects the corresponding pins according to the table above. Cables with 9 pins on one end and 25 on the other are common. Manufacturers of equipment with 8P8C connectors usually provide a cable with either a DB-25 or DE-9 connector (or sometimes interchangeable connectors so they can work with multiple devices). Poor-quality cables can cause false signals by crosstalk between data and control lines (such as Ring Indicator). If a given cable will not allow a data connection, especially if a Gender changer is in use, a Null modem may be necessary. Conventions For functional communication through a serial port interface, conventions of bit rate, character framing, communications protocol, character encoding, data compression, and error detection, not defined in RS 232, must be agreed to by both sending and receiving equipment. For example, consider the serial ports of the original IBM PC. This implementation used an 8250 UART using asynchronous start-stop character formatting with 7 or 8 data bits per frame, usually ASCII character coding, and data rates programmable between 75 bits per second and 115,200 bits per second. Data rates above 20,000 bits per second are out of the scope of the standard, although higher data rates are sometimes used by commercially manufactured equipment. Since most RS-232 devices do not have automatic baud rate detection, users must manually set the baud rate (and all other parameters) at both ends of the RS-232 connection. In the particular case of the IBM PC, as with most UART chips including the 8250 UART used by the IBM PC, baud rates were programmable with arbitrary values. This allowed a PC to be connected to devices not using the rates typically used with modems. 24
  37. 37. Not all baud rates can be programmed, due to the clock frequency of the 8250 UART in the PC, and the granularity of the baud rate setting. This includes the baud rate of MIDI, 31,250 bits per second, which is generally not achievable by a standard IBM PC serial port. MIDI-to-RS-232 interfaces designed for the IBM PC include baud rate translation hardware to adjust the baud rate of the MIDI data to something that the IBM PC can support, for example 19,200 or 38,400 bits per second. RTS/CTS handshaking In older versions of the specification, RS-232's use of the RTS and CTS lines is asymmetric: The DTE asserts RTS to indicate a desire to transmit to the DCE, and the DCE asserts CTS in response to grant permission. This allows for half-duplex modems that disable their transmitters when not required, and must transmit a synchronization preamble to the receiver when they are re-enabled. This scheme is also employed on present-day RS-232 to RS-485 converters, where the RS-232's RTS signal is used to ask the converter to take control of the RS-485 bus - a concept that does not otherwise exist in RS-232. There is no way for the DTE to indicate that it is unable to accept data from the DCE. A non-standard symmetric alternative, commonly called "RTS/CTS handshaking," was developed by various equipment manufacturers. In this scheme, CTS is no longer a response to RTS; instead, CTS indicates permission from the DCE for the DTE to send data to the DCE, and RTS indicates permission from the DTE for the DCE to send data to the DTE. RTS and CTS are controlled by the DTE and DCE respectively, each independent of the other. This was eventually codified in version RS-232-E (actually TIA-232-E by that time) by defining a new signal, "RTR (Ready to Receive)," which is CCITT V.24 circuit 133. TIA-232-E and the corresponding international standards were updated to show that circuit 133, when implemented, shares the same pin as RTS (Request to Send), and that when 133 is in use, RTS is assumed by the DCE to be ON at all times. Thus, with this alternative usage, one can think of RTS asserted (positive voltage, logic 0) meaning that the DTE is indicating it is "ready to receive" from the DCE, rather than requesting permission from the DCE to send characters to the DCE. Note that equipment using this protocol must be prepared to buffer some extra data, since a transmission may have begun just before the control line state change. 25
  38. 38. RTS/CTS handshaking is an example of hardware flow control. However, "hardware flow control" in the description of the options available on an RS-232- equipped device does not always mean RTS/CTS handshaking. 3-wire and 5-wire RS-232 Minimal “3-wire” RS-232 connections’ consisting only of transmit data, receive data, and ground, is commonly used when the full facilities of RS-232 are not required. Even a two-wire connection (data and ground) can be used if the data flow is one way (for example, a digital postal scale that periodically sends a weight reading, or a GPS receiver that periodically sends position, if no configuration via RS-232 is necessary). When only hardware flow control is required in addition to two-way data, the RTS and CTS lines are added in a 5-wire version. Seldom used features The EIA-232 standard specifies connections for several features that are not used in most implementations. Their use requires the 25-pin connectors and cables, and of course both the DTE and DCE must support them. a) Signal rate selection The DTE or DCE can specify use of a "high" or "low" signaling rate. The rates as well as which device will select the rate must be configured in both the DTE and DCE. The prearranged device selects the high rate by setting pin 23 to ON. b) Loopback testing Many DCE devices have a loopback capability used for testing. When enabled, signals are echoed back to the sender rather than being sent on to the receiver. If supported, the DTE can signal the local DCE (the one it is connected to) to enter loopback mode by setting pin 18 to ON, or the remote DCE (the one the local DCE is connected to) to enter loopback mode by setting pin 21 to ON. The latter tests the communications link as well as both DCE's. When the DCE is in test mode it signals the DTE by setting pin 25 to ON. A commonly used version of loopback testing does not involve any special capability of either end. A hardware loopback is simply a wire connecting complementary pins together in the same connector Loopback testing is often performed with a specialized DTE called a bit error rate tester (or BERT). 26
  39. 39. Timing Signals Some synchronous devices provide a clock signal to synchronize data transmission, especially at higher data rates. Two timing signals are provided by the DCE on pins 15 and 17. Pin 15 is the transmitter clock, or send timing (ST); the DTE puts the next bit on the data line (pin 2) when this clock transitions from OFF to ON (so it is stable during the ON to OFF transition when the DCE registers the bit). Pin 17 is the receiver clock, or receive timing (RT); the DTE reads the next bit from the data line (pin 3) when this clock transitions from ON to OFF. Alternatively, the DTE can provide a clock signal, called transmitter timing (TT), on pin 24 for transmitted data. Data is changed when the clock transitions from OFF to ON and read during the ON to OFF transition. TT can be used to overcome the issue where ST must traverse a cable of unknown length and delay, clock a bit out of the DTE after another unknown delay, and return it to the DCE over the same unknown cable delay. Since the relation between the transmitted bit and TT can be fixed in the DTE design, and since both signals traverse the same cable length, using TT eliminates the issue. TT may be generated by looping ST back with an appropriate phase change to align it with the transmitted data. ST loop back to TT lets the DTE use the DCE as the frequency reference, and correct the clock to data timing. Other Serial interfaces similar to RS-232  RS-422 (a high-speed system similar to RS-232 but with differential signaling)  RS-423 (a high-speed system similar to RS-422 but with unbalanced signaling)  RS-449 (a functional and mechanical interface that used RS-422 and RS-423 signals - it never caught on like RS-232 and was withdrawn by the EIA)  RS-485 (a descendant of RS-422 that can be used as a bus in multidrop configurations)  MIL-STD-188 (a system like RS-232 but with better impedance and rise time control)  EIA-530 (a high-speed system using RS-422 or RS-423 electrical properties in an EIA-232 pinout configuration, thus combining the best of both; supersedes RS- 449)  EIA/TIA-561 8 Position Non-Synchronous Interface Between Data Terminal Equipment and Data Circuit Terminating Equipment Employing Serial Binary Data Interchange 27
  40. 40.  EIA/TIA-562 Electrical Characteristics for an Unbalanced Digital Interface (low- voltage version of EIA/TIA-232)  TIA-574 (standardizes the 9-pin D-subminiature connector pinout for use with EIA-232 electrical signaling, as originated on the IBM PC/AT)  SpaceWire (high-speed serial system designed for use on board spacecraft). 2.2.4 MAX232 IC The MAX232 is an integrated circuit that converts signals from an RS-232 serial port to signals suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver and typically converts the RX, TX, CTS and RTS signals. The drivers provide RS-232 voltage level outputs (approx. ± 7.5 V) from a single + 5 V supply via on-chip charge pumps and external capacitors. This makes it useful for implementing RS-232 in devices that otherwise do not need any voltages outside the 0 V to + 5 V range, as power supply design does not need to be made more complicated just for driving the RS-232 in this case. The receivers reduce RS-232 inputs (which may be as high as ± 25 V), to standard 5 V TTL levels. These receivers have a typical threshold of 1.3 V, and a typical hysteresis of 0.5 V. The later MAX232A is backwards compatible with the original MAX232 but may operate at higher baud rates and can use smaller external capacitors – 0.1 μF in place of the 1.0 μF capacitors used with the original device.[1] The newer MAX3232 is also backwards compatible, but operates at a broader voltage range, from 3 to 5.5 V. Pin to pin compatible: ICL232, ST232, ADM232, and HIN232. Figure 2.5 MAX232 chip 28
  41. 41. Voltage Levels It is helpful to understand what occurs to the voltage levels. When a MAX232 IC receives a TTL level to convert, it changes a TTL Logic 0 to between +3 and +15 V, and changes TTL Logic 1 to between -3 to -15 V, and vice versa for converting from RS232 to TTL. This can be confusing when you realize that the RS232 Data Transmission voltages at a certain logic state are opposite from the RS232 Control Line voltages at the same logic state. To clarify the matter, see the table below. Table 2.3 RS-232 Voltage Levels RS232 Line Type & Logic Level RS232 Voltage TTL Voltage to/from MAX232 Data Transmission (Rx/Tx) Logic 0 +3 V to +15 V 0 V Data Transmission (Rx/Tx) Logic 1 -3 V to -15 V 5 V Control Signals (RTS/CTS/DTR/DSR) Logic 0 -3 V to -15 V 5 V Control Signals (RTS/CTS/DTR/DSR) Logic 1 +3 V to +15 V 0 V The MAX232 IC is used to convert the TTL/CMOS logic levels to RS232 logic levels during serial communication of microcontrollers with PC. The controller operates at TTL logic level (0-5V) whereas the serial communication in PC works on RS232 standards (-25 V to + 25V). This makes it difficult to establish a direct link between them to communicate with each other. The intermediate link is provided through MAX232. It is a dual driver/receiver that includes a capacitive voltage generator to supply RS232 voltage levels from a single 5V supply. Each receiver converts RS232 inputs to 5V TTL/CMOS levels. These receivers (R1 & R2) can accept ±30V inputs. The drivers (T1 & T2), also called transmitters, convert the TTL/CMOS input level into RS232 level. The transmitters take input from controller’s serial transmission pin and send the output to RS232’s receiver. The receivers, on the other hand, take input from transmission pin of RS232 serial port and give serial output to microcontroller’s receiver pin. MAX232 needs four external capacitors whose value ranges from 1µF to 22µF. 29
  42. 42. Table 2.4 TX and RX pin connection Microcontroller MAX232 RS232 Tx T1/2 In T1/2 Out Rx Rx R1/2 Out R1/2 In Tx Pin Diagram The following is the block diagram of the MAX232 IC. Figure 2.6 Pin diagram of MAX232 Pin Description: Table 2.5 Pins assignment of MAX232 Pin No Function Name 1 Capacitor connection pins Capacitor 1 + 2 Capacitor 3 + 3 Capacitor 1 - 4 Capacitor 2 + 5 Capacitor 2 - 6 Capacitor 4 - 7 Output pin; outputs the serially transmitted data at RS232 logic level; connected to receiver pin of PC serial port T2 Out 30
  43. 43. 8 Input pin; receives serially transmitted data at RS 232 logic level; connected to transmitter pin of PC serial port R2 In 9 Output pin; outputs the serially transmitted data at TTL logic level; connected to receiver pin of controller. R2 Out 10 Input pins; receive the serial data at TTL logic level; connected to serial transmitter pin of controller. T2 In 11 T1 In 12 Output pin; outputs the serially transmitted data at TTL logic level; connected to receiver pin of controller. R1 Out 13 Input pin; receives serially transmitted data at RS 232 logic level; connected to transmitter pin of PC serial port R1 In 14 Output pin; outputs the serially transmitted data at RS232 logic level; connected to receiver pin of PC serial port T1 Out 15 Ground (0V) Ground 16 Supply voltage; 5V (4.5V – 5.5V) Vcc 2.2.5 Relay A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming in from one circuit and re- transmitting it to another. Relays were used extensively in telephone exchanges and early computers to perform logical operations. History of a Relay A simple device, which we now call a relay, was included in the original 1840 telegraph patent of Samuel Morse. The mechanism described acted as a digital amplifier, repeating the telegraph signal, and thus allowing signals to be propagated as far as desired. This overcame the problem of limited range of earlier telegraphy schemes. The earlier ‘relay’ or ‘repeater’ of Edward Davy of 1837/1838 was used in his electric telegraph. 31
  44. 44. Figure 2.7 UK Q-style signaling relay and base. A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays". Figure 2.8 Automotive-style miniature relay, dust cover is taken off Basic Design and Operation of a Relay A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core, an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one or more sets of contacts (there are two in the relay pictured). The armature is hinged to the yoke and mechanically linked to one or more sets of moving contacts. It is held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other relays may have more or fewer sets of contacts depending on their function. The relay in the picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the printed circuit board (PCB) via the yoke, which is soldered to the PCB. 32
  45. 45. When an electric current is passed through the coil it generates a magnetic field that activates the armature and the consequent movement of the movable contact either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing. When the coil is energized with direct current, a diode is often placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components. Some automotive relays include a diode inside the relay case. Alternatively, a contact protection network consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil is designed to be energized with alternating current (AC), a small copper "shading ring" can be crimped to the end of the solenoid, creating a small out-of-phase current which increases the minimum pull on the armature during the AC cycle.[1] A solid-state relay uses a thyristor or other solid-state switching device, activated by the control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a light-emitting diode (LED) coupled with a photo transistor) can be used to isolate control and controlled circuits. Pole and Throw Since relays are switches, the terminology applied to switches is also applied to relays. A relay will switch one or more poles, each of whose contacts can be thrown by energizing the coil in one of three ways:  Normally-open (NO): Contacts connect the circuit when the relay is activated; the circuit is disconnected when the relay is inactive. It is also called a Form A contact or "make" contact. NO contacts can also be distinguished as "early-make" or NOEM, which means that the contacts will close before the button or switch is fully engaged.  Normally-closed (NC): contacts disconnect the circuit when the relay is activated; the circuit is connected when the relay is inactive. It is also called a Form B contact or "break" contact. NC contacts can also be distinguished as "late-break" or NCLB, 33
  46. 46. which means that the contacts will stay closed until the button or switch is fully disengaged.  Change-over (CO): or double-throw (DT), contacts control two circuits: one normally-open contact and one normally-closed contact with a common terminal. It is also called a Form C contact or "transfer" contact ("break before make"). If this type of contact utilizes a "make before break" functionality, then it is called a Form D contact. The following designations are commonly encountered:  SPST – Single Pole Single Throw. These have two terminals which can be connected or disconnected. Including two for the coil, such a relay has four terminals in total. It is ambiguous whether the pole is normally open or normally closed. The terminology "SPNO" and "SPNC" is sometimes used to resolve the ambiguity.  SPDT – Single Pole Double Throw. A common terminal connects to either of two others. Including two for the coil, such a relay has five terminals in total.  DPST – Double Pole Single Throw. These have two pairs of terminals. Equivalent to two SPST switches or relays actuated by a single coil. Including two for the coil, such a relay has six terminals in total. The poles may be Form A or Form B (or one of each).  DPDT– Double Pole Double Throw. These have two rows of change-over terminals. Equivalent to two SPDT switches or relays actuated by a single coil. Such a relay has eight terminals, including the coil.  The "S" or "D" may be replaced with a number, indicating multiple switches connected to a single actuator. For example 4PDT indicates a four pole double throw relay (with 14 terminals).  EN 50005 are among applicable standards for relay terminal numbering; a typical EN 50005-compliant SPDT relay's terminals would be numbered 11, 12, 14, A1 and A2 for the C, NC, NO, and coil connections, respectively. Figure 2.9 Circuit symbols of relays. (C denotes the common terminal in SPDT and DPDT types.) 34
  47. 47. Uses of Relays oAmplify a digital signal, switching a large amount of power with a small operating power. Some special cases are: oA telegraph relay, repeating a weak signal received at the end of a long wire oControlling a high-voltage circuit with a low-voltage signal, as in some types of modems or audio amplifiers, o Controlling a high-current circuit with a low-current signal, as in the starter solenoid of an automobile. 2.2.6 LCD A liquid crystal display (LCD) is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals (LCs). LCs do not emit light directly. LCDs are used in a wide range of applications, including computer monitors, television, instrument panels, aircraft cockpit displays, signage, etc. They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs have replaced cathode ray tube (CRT) displays in most applications. They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they cannot suffer image burn-in. LCDs are, however, susceptible to image persistence. LCDs are more energy efficient and offer safer disposal than CRTs. Its low electrical power consumption enables it to be used in battery- powered electronic equipment. It is an electronically modulated optical device made up of any number of segments filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome. The most flexible ones use an array of small pixels. The earliest discovery leading to the development of LCD technology, the discovery of liquid crystals, dates from 1888. By 2008, worldwide sales of televisions with LCD screens had surpassed the sale of CRT units. Following figure is a 16x2 LCD. Figure 2.10 A general purpose alphanumeric LCD, with two lines of 16 characters. 35
  48. 48. Monochrome passive-matrix LCDs were standard in most early laptops (although a few used plasma displays) and the original Nintendo Game Boyuntil the mid-1990s, when color active-matrix became standard on all laptops. The commercially unsuccessful Macintosh Portable (released in 1989) was one of the first to use an active-matrix display (though still monochrome). Passive-matrix LCDs are still used today for applications less demanding than laptops and TVs. In particular, portable devices with less information content to be displayed, where lowest power consumption (no backlight), low cost and/or readability in direct sunlight are needed, use this type of display. Advantages and Disadvantages In spite of LCDs being a well proven and still viable technology, as display devices LCDs are not perfect for all applications. Advantages  Very compact and light.  Low power consumption.  No geometric distortion.  Little or no flicker depending on backlight technology.  Not affected by screen burn-in.  Can be made in almost any size or shape.  No theoretical resolution limit. Disadvantages  Limited viewing angle, causing color, saturation, contrast and brightness to vary, even within the intended viewing angle, by variations in posture.  Bleeding and uneven backlighting in some monitors, causing brightness distortion, especially toward the edges.  Smearing and ghosting artifacts caused by slow response times (>8 ms) and "sample and hold" operation.  Fixed bit depth, many cheaper LCDs are only able to display 262,000 colors. 8-bit S-IPS panels can display 16 million colors and have significantly better black level, but are expensive and have slower response time.  Low bit depth results in images with unnatural or excessive contrast.  Input lag  Dead or stuck pixels may occur during manufacturing or through use. 36
  49. 49. Chapter 3 Working of VTS 3.1 Schematic Diagram of VTS 3.2 Circuit Description The hardware interfaces to microcontroller are LCD display, GSM modem and GPS receiver. The design uses RS-232 protocol for serial communication between the modems and the microcontroller. A serial driver IC is used for converting TTL voltage levels to RS-232 voltage levels. When the request is sent by the number at the modem, the system automatically sends a return reply to that mobile indicating the position of the vehicle in terms of latitude and longitude. Figure 3.1 Schematic diagram of vehicle tracing using GSM and GPS 37
  50. 50. 3.3 Circuit Operation The project is vehicle positioning and navigation system we can locate the vehicle around the globe with 8052 micro controller, GPS receiver, GSM modem, MAX 232, Power supply. Microcontroller used is AT89S52. The code is written in the internal memory of Microcontroller i.e. ROM. With help of instruction set it processes the instructions and it acts as interface between GSM and GPS with help of serial communication of 8052. GPS always transmits the data and GSM transmits and receive the data. GPS pin TX is connected to microcontroller via MAX232. GSM pins TX and RX are connected to microcontroller. 3.3.1 Power The power is supplied to components like GSM, GPS and Micro control circuitry using a 12V/3.2A battery .GSM requires 12v,GPS and microcontroller requires 5v .with the help of regulators we regulate the power between three components. 3.3.2 Serial ports Microcontroller communicates with the help of serial communication. First it takes the data from the GPS receiver and then sends the information to the owner in the form of SMS with help of GSM modem. 3.4 Operating procedure: a) To store a Number into the kit i. Place a jumper at the pin no 32 “Store Number” as shown in the circuit diagram. ii. Switch on the kit. iii. Wait until you see “Waiting for Call” on the LCD display. iv. Now call from the mobile number from which you need to store the number. v. Wait until you see “Number stored” on the LCD. vi. Now remove the Jumper. b) Normal Operation i. Switch on the kit and wait until you see the Latitude and longitude on the display. ii. Now give a call from any mobile iii. The kit will send the location and UTC time to the number stored in its memory. 38
  51. 51. iv. For emergency the user can press the Button to send the Location to the number stored. v. For photos of this project check this link. Initially the GPS continuously takes the data from the satellite and stores the latitude and longitude positions in microcontroller’s buffer. If we want to know the path of the vehicle we need to send a message to the GSM which gets activated by receiving our message .at the same instant the GPS gets deactivated with the help of relay. As soon as the GSM gets activated it takes the last received latitude and longitude positions from the buffer and sends a message to the particular number which is executed in the program. After the message has been sent to the user the GSM gets deactivated and similarly the GPS gets activated. This is cyclic process 39
  52. 52. Chapter 4 Microcontroller AT 89S52 Why we use AT 89S52? AT89S52 microcontroller is a great family compatible with Intel MCS-51 . Atmel AT89S52 is created by, indicated by the initials "AT". This microcontroller has a low consumption, but 8-bit CMOS gives high performance with an internal flash memory of 8K bytes. This is done using flash memory technology and high density belonging to Atmel and is compatible with standard 80C51. Flash memory chip allows internal or scheduled to be reprogrammed by a non-volatile memory. By combining an 8-bit CPU with Flash memory programmable monolithic core, Atmel AT89S52 is very powerful microcontroller has high flexibility and is the perfect solution for many embedded applications. A microcontroller is an electronic structure of small size, usually containing a processor, memory and peripheral input / output programmable. Applications that use microcontrollers are automatic control, in areas such as car production, medical devices, remote control and more of the same gender. In 1976, Intel created the first microcontroller family called MCS. MCS 48 MCS 51 standard appearing in 1980. Currently, Intel does not make such microcontrollers, but major manufacturers such as Atmel and Infineon continued creating these devices. 4.1 Features The main features of the microcontroller are:  Compatibility with the MCS 51 family;  8-bit CPU frequency up to 33MHz;  RAM: 256 Bytes;  Flash memory: 8K bytes;  32 lines of programming input / output general nature;  8 sources of interruptions organized on two levels of priority;  3 timers / counters of 16 bits;  Watchdog Timer;  two data pointers;  1 serial port (full duplex UART);  ISP programming interface of 8K bytes; 40
  53. 53.  supports up to 10 000 rewrites;  contains the oscillator;  Short programming time. 4.2 The Pin Configuration AT89S52 microcontroller is a 40-pin; its meaning is expressed below. Pin number in parentheses is that given the fact that pin 1 is top left, and pin 40 in the top right. Vcc (40): Supply Voltage; GND (20): Grounding; Port 0 (39-32): Port 0 is a bidirectional port input / output 8-bit. As an output port, each pin is allotted eight TTL inputs. When port pins 0 are registered with a logical value, they can be used as high impedance inputs. Port 0 can also be configured as the least significant address and data during access to external program and data memory. Port 0 is also the recipient code during Flash programming and gives the result bits from the verification program. Closing transistor is required during program verification. Port 1 (1-8): Port 1 is also a bidirectional port input / output with internal pull-up (transistor is automatically closed). But for an output port can support four TTL inputs. When port 1 is written with a logical value, i.e. the transistor is closed; we can use the port for reading, otherwise, if the transistor is open for write port use. Port 1 also receives the least significant address bits during Flash programming and verification. In addition, pins 0 and 1 of port1 can be configured as timers and counters it is, and pins 5, 6, and 7 are used for programming interface. Port 2 (21-28): Port 2 is also a bidirectional port input / i.e. tire 8-bit internal pull- up. Port 2 is the one who gives the most significant bits of the address during extraction from external memory and external memory while accessing the data using 16-bit addresses. In this mode of use, Port 2 uses strong internal pull up the issue of a logical value. While access to external data memory that utilizes 8-bit addresses, port 2 is used for special function registers. Port 2 also receives the most significant address bits and some control signals during Flash programming and verification. Port 3 (10-17): Port 3 is also a bidirectional port input / output 8-bit internal pull-up by acting as port 1 and 2. Port 3 receives control signals for Flash memory programming Other special functions you can perform port 3 are:  pin 0 is there an alternative entrance to the serial port (RXD);  pin 1 is used as serial port output (TXD); 41
  54. 54.  pins 2 and 3 are used for external interrupt (INT0 #, # INT1);  pins 4 and 5 can be used interchangeably as timers (T0 and T1);  pin 6 is used as a signal to external memory write (# WR);  Pin 7 is used as the external signal read from memory (RD #). RST (9): acts as a reset RST entry. A high value on this pin between two machine cycles while the oscillator work, reset the device. This pin acts high for 98 oscillator periods after the watchdog stops. To disable this feature using DISRTO bit of special function registers at exactly the 8EH. The default state of bit DISRTO, feature RESET is active HIGH. ALE / PROG # (30): THE acronym comes from the Address Latch Enable, and this is what command buffer that stores the least significant address. During Flash memory programming this pin serves as input pulse programming: # PROG (Program Pulse Input). For normal operation, ALE issued at a time constant equal to 1/6 of oscillator frequency and can be used as a timer or external clock. By request, executes the function that OF can be disabled by setting bit special register at 8EH with logic value 0. With this bit set, ALE is active only for the instructions MOVX and MOVC. Disabling OF bit has no effect if the microcontroller is in external execution mode. PSEN (29): Acronym PSEN Program Store Enable is the control signal and means for external program memory. When AT89S52 code running external program memory, PSEN # is activated 2 times for each machine cycle, except the activation signal PSEN # is omitted during external data memory access. EA / VPP (31): EA acronym stands External Access Enable. # It must be connected to GRD to enable the device to extract the code from external program memory from address 0000H to address internal program executions FFFFH. Pentru # EA must be connected to Vcc. XTAL1 (19): XTAL1 is used as input to the inverting oscillator amplified the input clock operating circuit. XTAL2 (18): XTAL2 oscillator inverter output is amplified. 4.2.1 Special Function Registers (SFR) Not all addresses in the area where there are special function registers are occupied and the unoccupied may be absent on the chip. Access to read from these addresses will in general return random data and write access to will have an effect 42
  55. 55. indefinitely. Programmers should avoid writing in these locations, because these locations can be used in future for new features. In this case the reset or inactivation of these new bits will always be 0. Timer Registers: Control and status bits are contained in registers T2CON and T2MOD for timer 2. The pair of registers (RCAP2H, RCAP2L) are registers purchase or reload timer 2 for 16-bit mode and 16-bit acquisition mode auto reload. Registers of interruptions: Individual interrupt enable bits are in register IE. For the six types of interrupt sources can be set two levels of priority in the IP register. 4.3 Memory Organization MCS-51 family devices have separate address and data program. Up to 64K bytes each program or data memory can be addressed. a) Program memory If EA is pin # connected the GRD program calls are directed to external memory. If EA # is connected to Vcc, calls the program at address 0000H to 1FFFH are directly to internal memory, while those at 2000H up to FFFFH are directed to external memory. b) Data memory AT89S52 has a RAM of 256 bytes. The 128 Bytes additional to the 128 basic families occupies an address space parallel to the Registrar of Special Functions, and that these additional bytes of special function registers are accessible addresses, but physically they are in different spaces. When an instruction accesses an internal location in 7fh address, addressing mode used in the instruction specifies that the CPU accesses the upper 128 bytes of RAM or the RFS. It uses direct addressing to access the RFS space, and indirect addressing the senior access bytes RAM. 4.4 Watch Dog Timer: Watchdog Timer (WDT) is used as a recovery method in situations where the CPU is under software problems. The WDT counter consists of a 14-bit Watchdog Timer and Reset (WDTRST) which is in RFS. By default, the WDT is disabled, for activation, the user successively 0E1H 01EH and WDTRST register, i.e. the RFS's location 0A6H. Cans WDT is active, it will increment every machine cycle, while the oscillator will run. Rest period is dependent on the external clock frequency. The only way to disable the WDT is reset site. When WDT exceeds the maximum limit will send a reset pulse RST pin HIGH. 43
  56. 56. 4.4.1 Watchdog Timer for both modes of operation Power-down mode means stopping off WDT's oscilloscope. During Power-down mode of operation, the user must not maintain the WDT. There are two ways to exit Power-down mode: by a hard reset or via an external interrupt is Priority Power-down mode. When Power-down exits through a hardware reset, WDT service should act as if AT89S52 is reset. Power-down Exit through an interrupt is significantly different behavior. Interruption is maintained sufficiently long as the oscillator to stabilize. When termination is carried high, it is served. To prevent the WDT from resetting the device interrupt pin is held low, the WDT will not start until the interrupt will not be extended to a high level. This means, that the WDT will be cleared during the interrupt function to exit Power-down mode. To ensure that the WDT will not be exceeded during some states out of Power-down, it is better to be reset before entering Power-down mode. Before entering the Idle mode, bit WDIDLE the RFS is used to determine where to continue the WDT when it becomes active. The WDT continues to count during Idle mode as the default state. To prevent the WDT to reset the AT89S52 during Idle mode, the user should always set a timer that will periodically exit Idle, will service the WDT and enter Idle mode again. The WDT enabled WDIDLE bit will stop the count in Idle mode and continue counting out of the way. a) Switches AT89S52 is a vector of six stops: two external interrupts (INT0 # and #, INT2), three timers interrupts (Timer 0, 1 and 2) and serial port interrupt. Each of these interrupt sources can be individually enabled and disabled by setting or deleting a bit of special function registers IE. IE also contains a global disable bit, EA, which disables all interrupts at the same time. Bit position 6 is not implemented. But the programmer should not use this bit; it can be used in future AT89 products family. Interruption of Timer 2 is generated by "or logic" between bits TF2 and EXF2 you register T2CON.None of these indicators is not deleted when routine hardware orders indicate that area. In fact, routine order to determine which of the two bits TF2 or EXF2 generated interrupts, and that bit will be set in software. b) The idle In Idle mode, CPU is put into hibernation, while all peripherals remain active. The mode is invoked by software. Content on chip RAM and all special function registers remain unchanged while this mode is set. Idle mode can be enabled over any break or 44
  57. 57. hardware reset. When idle mode is terminated by a hardware reset, the device normally resumes program execution from where it was interrupted by two machine cycles before the internal reset algorithm to take control. The hardware on the same plate to prevent access to internal RAM during this event, but access to ports is blocked. To eliminate the possibility of unexpected writings of a port pin when idle mode is terminated by reset, the instruction as it is one that invokes idle mode should not write to a port pin or external memory. c) The power-down Power-down mode, the oscillator is set and instructions for calling Power-down mode is the last instruction executed. Track RAM on chip and special function registers retain their values until the Power-down mode ends. Exit Power-down can be initiated both by activating a hardware reset or external interrupt. Reset registry values change with special but not modify RAM on chip. Reset can be activated before VCC to return to its operating level and must remain active long enough to allow the oscillator resetting and stabilization. 45