Chapter 1
1.1 INTRODUCTION TO EMBEDDED SYSTEMS
An embedded system is a combination of hardware ,software ,mechanical and other specific components together combine to form a design that performs a specific function . An embedded system is mainly a microcontroller based software driven system to perform specific operations that is for automated robotic operations operating on diverse physical variables and in diverse environments and into highly competitive environment.
Microcontrollers with 32 and 64bit are used in embedded systems in general .Devices like mobile phones ,Personal digital Assistant etc are evident .And 8 and 16 bit microcontrollers Generally 8,16 Bit Controllers used with an minimal operating systems and hardware layout designed for the specific purpose. Devices like washing machines and microwave ovens are examples for minimal operating systems.
1.2SYSTEM DESIGN CALLS:
Figure 1(a): design cycles of embedded systems
EMBEDDED SYSTEM DESIGN CYCLE
Figure.1(b):“V Diagram” of embedded systems
1.3 Characteristics of Embedded System
An embedded system is system hidden inside a product other than a personal computer device.
They will encounter a number of difficulties when writing embedded system software in addition to implementation of the applications of embedded systems.In embedded systems it can handle lot of data and lot of data is to be tested before implementation. Testability–Setting up equipment to test embedded software can be difficult.
Debugging–Without a screen or a keyboard, handling the situation is little difficult.
Reliability – This can handle any situation without human intervention.
Memory space – Memory is limited in embedded systems
Power consumption – These embedded systems run on battery systems and are portable in nature.
Processor hogs –Computing requires very high cost in this system.
Cost – Reducing the cost of the hardware is a concern in many embedded system projects; software systems are difficult to implement.
Embedded systems have a microprocessor/ microcontroller and a memory. Some have a serial port or a network connection. They usually do not have keyboards, screens or disk drives.
1.4 APPLICATIONS
1) Military and aerospace embedded software applications
2) Communication Applications
3) Industrial automation and process control software
4) Mastering the complexity of applications.
5) Reduction of product design time.
6) Real time processing of ever increasing amounts of data.
7) Intelligent, autonomous sensors.
1.5 CLASSIFICATION
Real Time Systems.
It is one which has to respond to events within a specified deadline.A right answer after the dead line is a wrong answer.
1.5.1 RTS CLASSIFICATION
Hard Real Time Systems
Soft Real Time System
1.5.1.aHARD REAL TIME SYSTEM
“Hard” real-time systems have very narrow response time.
Example: Nuclear power system, Cardiac pacemaker.
Chapter 2
BLOCK DIAGRAM OF WIRELESS BLACKBOX
Figure.2(a):block diagram of wireless blackbox
2.1 INTRODUCTION TO WIRELESS BLACK BOX
Accidents have been a major problem in the society which are ruining the lives of many individuals. These accidents have varied reasons and are difficult to be obtained .The main cause of the accident may be due to any reasons but the main issue is that the accident victims are not able to undergo proper treatment on the right time as the occurrence of accident is not known to the family members and so the treatment is getting delayed which is resulting in loss of lives of people. This accident detection is possible with the help of our project that is Wireless Black Box with MEMS Accelerometer. Using this the location and position of the accident vehicle can be detected .Therefore a system is needed such that the accident vehicle to be detected and accident victims life to be saved. The other issue faced with the accidents is that the cause of the accident is unknown such that police enquiry is not done completely as the exact causes are unknown and it misleads to improper investigation. These problems can be rectified using Wireless Black Box using MEMS Accelerometer.
This project is to develop a wireless black box using MEMS accelerometer and GPS tracking system for accidental monitoring. Mems accelerometer is used to detect the motion of the object that is the sensory movements of the object are detected. Based on the sensory movements if any unusual accelerations occur it detects that an accident has occurred and this information is detected with position using a GPS Module and messages are sent to the saved family members and other emergency members using GSM module.GPS module is used to detect the location and position of the object using coordinates that is using x-axis ,y-axis and z-axis. GSM module is used to send the located position of the accident to the saved numbers of the family members and other numbers using the module .We use LPC 2148 microcontroller for the detection ,position and message sending as the information is controlled by the LPC 2148 microcontroller for the GPS,GSM and MEMS Accelerometer. This project also involves playback recording using a playback recorder such that for a duration of one minute during the occurrence of the accident the voices of the accident victims are recorded such that the exact cause of the accident can be known so that it will also be helpful for the police Investigation. Therefore these services which are included in the project have a great impact on accident detection ,location and also voice recording are very much helpful accidental monitoring of vehicles.
2.2 Existing system
In the existing system this accident detection and monitoring of the vehicles is mainly used for the airplanes such that most of the accident detections and occurrence are known using this system .These are mostly used for the higher end vehicles because of its higher cost .The implementation of Blck Box using Mems Accelerometer is very useful in tracking of vehicles and accident detection of vehicles and also playback recording.
2.3 Design of proposed hardware system
In this project we are detecting the position of the accident vehicle using the Mems Accelerometer motion ,that is due to the unusual accelerations of the MEMS Accelerometer the position of the vehicle is detected using GPS module and the accident location is sent to the family members using GSM module and the whole is controlled by LPC2148 microcontroller to perform all these actions. Another feature added in this project is that a playback recorder is introduced so that the voices are detected during the occurrence of the accident. Above all even the cost factor is also reduced such that this can be introduced in all vehicles for accident detection By using GSM we can send the message to family members, emergency medical service and nearest hospital.
Chapter 3
HARDWARE REQUIREMENTS
HARDWARE COMPONENTS FOR WIRELESS BACKBOX:
1. POWER SUPPLY
2. TRANSFORMER (230 – 12 V AC)
3. VOLTAGE REGULATOR (LM 7805)
4. RECTIFIER
5. FILTER
6. LPC 2148 MICROCONTROLLER
7. GSM MODULE
8. GPS MODULE
9. PUSH BUTTON
10. 1N4007
11. LED
12. LCD
13. RESISTOR
14. CAPACITOR
15. GPS
16. LCD
3.1 POWER SUPPLY
Power supply is a reference to a source of electrical power. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others.
The available voltage signal from the mains is 230V/50Hz which is an AC voltage, but the required is DC voltage(no frequency) with the amplitude of +5V and +12V for various applications.
In this section we have Transformer, Bridge rectifier, are connected serially and voltage regulators for +5V and +12V (7805 and 7812) via a capacitor (1000µF) in parallel are connected parallel as shown in the circuit diagram below. Each voltage regulator output is again is connected to the capacitors of values (100µF, 10µF, 1 µF, 0.1 µF) are connected parallel through which the corresponding output(+5V or +12V) are taken into consideration.
Figure.3(a):Power supply circuit for wireless blackbox
3.2 TRANSFORMER:
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled electrical conductors
The secondary induced voltage VS, of an ideal transformer, is scaled from the primary VP by a factor equal to the ratio of the number of turns of wire in their respective windings:
The transformer is based on two principles: firstly, that an electric current can produce a magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). By changing the current in the primary coil, it changes the strength of its magnetic field; since the changing magnetic field extends into the secondary coil, a voltage is induced across the secondary.
A simplified transformer design is shown below. A current passing through the primary coil creates a magnetic field. The primary and secondary coils are wrapped around a core of very high magnetic permeability, such as iron; this ensures that most of the magnetic field lines produced by the primary current are within the iron and pass through the secondary coil as well as the primary coil.
Fig.3(b):An ideal step-down transformer showing magnetic flux in the core
Induction law:The voltage induced across the secondary coil may be calculated from Faraday’s law of induction, which states that:
Where VS is the instantaneous voltage, NS is the number of turns in the secondary coil and Φ equals the magnetic flux through one turn of the coilThe area is constant, being equal to the cross-sectional area of the transformer core, whereas the magnetic field varies with time according to the excitation of the primary. Since the same magnetic flux passes through both the primary and secondary coils in an ideal transformer, the instantaneous voltage across the primary winding equals
Taking the ratio of the two equations for VS and VP gives the basic equationfor stepping up or stepping down the voltage
If the secondary coil is attached to a load that allows current to flow, electrical power is transmitted from the primary circuit to the secondary circuit. Ideally, the transformer is perfectly efficient; all the incoming energy is transformed from the primary circuit to the magnetic field and into the secondary circuit. If this condition is met, the incoming electric power must equal the outgoing power.
Pincoming = IPVP = Poutgoing = ISgiving the ideal transformer equation
Fig.3(c):Transformer Circuit
Pin-coming = IPVP = Pout-going = ISVS
giving the ideal transformer equation
If the voltage is increased (stepped up) (VS>VP), then the current is decreased (stepped down) (IS<IP) by the same factor. Transformers are efficient so this formula is a reasonable approximation.
If the voltage is increased (stepped up) (VS>VP), then the current is decreased (stepped down) (IS<IP) by the same factor. Transformers are efficient so this formula is a reasonable approximation.
The impedance in one circuit is transformed by the square of the turns ratio. For example, if an impedance ZS is attached across the terminals of the secondary coil, it appears to the primary circuit to have an impedance of
This relationship is reciprocal, so that the impedance ZP of the primary circuit appears to the secondary to be
The changing magnetic field induces an electromotive force (EMF) across each winding. Since the ideal windings have no impedance, they have no associated voltage drop, and so the voltages VP and VS measured at the terminals of the transformer, are equal to the corresponding EMFs. The primary EMF, acting as it does in opposition to the primary voltage, is sometimes termed the “back EMF”. This is due to Lenz’s law which states that the induction of EMF would always be such that it will oppose development of any such change in magnetic field
3.3 BRIDGE RECTIFIER
A diode bridge or bridge rectifier is an arrangement of four diodes in a bridge configuration that provides the same polarity of output voltage for any polarity of input voltage. When used in its most common application, for conversion of alternating current (AC) input into direct current (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a center-tapped transformer design, but has two diode drops rather than one, thus exhibiting reduced efficiency over a center-tapped design for the same output voltage.
Basic Operation:
When the input connected at the left corner of the diamond is positive with respect to the one connected at the right hand corner, current flows to the right along the upper colored path to the output, and returns to the input supply via the lower one.
Fig.3(d):Bridge Rectifier Circuit
Fig.3(e):Bridge Rectifier Circuit(Right Terminal Positive)
That is, it permits normal functioning when batteries are installed backwards or DC input-power supply wiring “has its wires crossed” (and protects the circuitry it powers against damage that might occur without this circuit in place).
Prior to availability of integrated electronics, such a bridge rectifier was always constructed from discrete components.
Fig.3(f):Bridge Rectifier Analysis
Fig.3(g):Bridge Rectifier with Output voltage
The function of this capacitor, known as a reservoir capacitor (aka smoothing capacitor) is to lessen the variation in (or ‘smooth’) the rectified AC output voltage waveform from the bridge.
Accidents have been a major problem in the society which are ruining the lives of many individuals. These accidents have varied reasons and are difficult to be obtained .The main cause of the accident may be due to any reasons but the main issue is that the accident victims are not able to undergo proper treatment on the right time as the occurrence of accident is not known to the family members and so the treatment is getting delayed which is resulting in loss of lives of people. This accident detection is possible with the help of our project that is Wireless Black Box with MEMS Accelerometer. Using this the location and position of the accident vehicle can be detected .Therefore a system is needed such that the accident vehicle to be detected and accident victims life to be saved. The other issue faced with the accidents is that the cause of the accident is unknown such that police enquiry is not done completely as the exact causes are unknown and it misleads to improper investigation. These problems can be rectified using Wireless Black Box using MEMS Accelerometer.
Because a bleeder sets a minimum current drain, the regulation of the circuit, defined as percentage voltage change from minimum to maximum load, is improved. However in many cases the improvement is of insignificant magnitude.
Output can also be smoothed using a choke and second capacitor. Some early console radios created the speaker’s constant field with the current from the high voltage (“B +”) power supply, which was then routed to the consuming circuits, (permanent magnets were considered too weak for good performance) to create the speaker’s constant magnetic field. The speaker field coil thus performed 2 jobs in one: it acted as a choke, filtering the power supply, and it produced the magnetic field to operate the speaker.
3.4 VOLTAGE REGULATOR 7805
Features
• Output Current up to 1A.
• Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V.
• Thermal Overload Protection.
• Short Circuit Protection.
• Output Transistor Safe Operating Area Protection.
Fig.3(h):Voltage Regulator Circuit
Description
The LM78XX/LM78XXA series of three-terminal positive regulators are available in the TO-220/D-PAK package and with several fixed output voltages, making them useful in a Wide range of applications. Each type employs internal current limiting, thermal shutdown and safe operating area protection, making it essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A output Current. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltages and currents.
Fig.3(i):Block diagram of voltage regulator
TABLE 3(a):Ratings of the voltage regulator
3.5 RECTIFIER
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), current that flows in only one direction, a process known as rectification. Rectifiers have many uses including as components of power supplies and as detectors of radio signals. It converts A.C. into pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used because of its merits like good stability and full wave rectification. In positive half cycleonly two diodes( 1 set of parallel diodes) will conduct, in negative half cycle remaining two diodes will conduct and they will conduct only in forward bias only.
Fig.3(j):Full Wave Rectifier
3.6 FILTER
Capacitive filter is used in this project
Fig.3(k):output waveform from filter
3.7 LPC 2148 ARM MICROCONTROLLER
3.7.1GENERAL DESCRIPTION OF LPC 2148:
The LPC2148 microcontrollers are based on a 16-bit/32-bit ARM7TDMI-CPU with real-time emulation and embedded trace support, that combine microcontroller with embedded high speed flash memory ranging from 32 kB to 512 kB. Serial communications interfaces ranging from a USB 2.0 Full-speed device, multiple UARTs, SPI, SSP to I2C-bus and on-chip SRAM of 8 kB up to 40 kB, make these devices very well suited for communication gateways and protocol converters, soft modems, voice recognition and low end imaging, providing both large buffer size and high processing power. Various 32-bit timers, single or dual 10-bit ADC(s), 10-bit DAC, PWM channels and 45 fast GPIO lines with up to nine edge or level sensitive external interrupt pins make these microcontrollers suitable for industrial control and medical systems.
Fig.3(l):pin diagram of LPC 2148
3.7.2 MEMORY ORGANIZATION
On-Chip Flash Program Memory
The LPC2148 incorporates a 512 kB flash memory system. This memory may be used for both code and data storage. Programming of the flash memory The application program may also erase and/or program the flash while the application is running, a great degree of flexibility firmware upgrades, etc. Due to the architectural solution chosen for an on-chip boot loader, flash memory available for user’s code on LPC2148 is 500 kB. The LPC2148 flash memory provides a minimum of 100,000 erase/write cycles and 20 years of data-retention
3.7.3 Memory Map
The LPC2148 memory map incorporates several distinct regions, as shown in Fig 4.2 In addition, the CPU interrupt vectors may be remapped to allow them to reside in either flash memory (the default) or on-chip static RAM.
Fig.3(m):Memorymap
3.7.4 Interrupt Controller
The Vectored Interrupt Controller (VIC) accepts all of the interrupt request inputs and categorizes them as Fast Interrupt Request (FIQ), non-vectored IRQ as defined by programmable settingsThe fastest possible FIQ latency is achieved when only one request is classified as FIQ. Interrupt Sources
Each peripheral device has one interrupt line connected to the Vectored Interrupt Controller, but may have several internal interrupt flags. Individual interrupt flags may also represent more than one interrupt source.
3.7.6 Fast General Purpose Parallel I/O (GPIO)
Device pins that are not connected to a specific peripheral function are controlled by the GPIO registers.
3.7.710-bit ADC
The LPC2141/42 contains one and the LPC2148 contains two analog to digital converters. These converters are single 10-bit successive approximation analog to digital converters. While ADC0 has six channels, ADC1 has eight channels These single 10-bit successive approximation analog to digital converters. While ADC0 has six channels, ADC1 has eight channels. Therefore, total number of available ADC inputs for LPC2141/42 is 6 and for LPC2148 are 14.
3.7.8 10-bit DAC
The DAC enables the LPC2148 to generate a variable analog output. The maximum DAC output voltage is the VREF voltage.
3.7.9 USB 2.0 device controller
Allows dynamic switching between CPU controlled and DMA modes (only in LPC2146/48).Double buffer implementation for bulk and isochronous endpoints given data transfer. During a data transfer the master always sends a byte of data to the slave, and the slave always sends a byte of data to the master.
3.7.10 SSP serial I/O controller
The LPC2148 each contains one SSP. The SSP controller is capable of operation on a SPI, 4-wire SSI or Microwire bus. It can interact with multiple masters and slaves on the bus. However, only a single master and a single slave can communicate on the bus during a given data transfer. The SSP supports full duplex transfers, with data frames of 4 bits to 16 bits of data flowing from the master to the slave and from the slave to the master. Often only one of these data flows carries meaningful data.
3.7.11 General purpose timers/external event counters
The Timer/Counter is designed to count cycles of the peripheral clock (PCLK) or an externally supplied clock and optionally generate interrupts or perform other actions at specified timer values, based on four match registers. It also includes four capture inputs to trap the timer value when an input signal transitions. Multiple pins can be selected to perform a single capture or match function, providing an application with ‘or’ and ‘and’, as well as ‘broadcast’ functions among them.
3.7.15 SYSTEM CONTROL
3.7.15.1 Crystal Oscillator
On-chip integrated oscillator operates with external crystal in range of 1 MHz to 25 MHz. The oscillator output frequency is called fosc and the ARM processor clock frequency is referred to as CCLK for purposes of rate equations, etc. fosc and CCLK are the same value unless the PLL is running and connected.
3.7.15.2 PLL
The PLL accepts an input clock frequency in the range of 10 MHz to 25 MHz. The input frequency 10 MHz to 60 MHz with a Current Controlled Oscillator (CCO). The CCO operates in the range of 156 MHz to 320 MHz, so there is an loop to keep the CCO within its frequency range while the PLL is providing the desired output frequency. The output divider may be set to divide by 2, 4, 8, or 16 to produce the output clock. Since value is 2, it is insured that the PLL output has a 50 % duty cycle. The PLL is turned off and bypassed following a chip reset and may be enabled by software. The program must configure and activate the PLL, wait for the PLL to Lock, then connect to the PLL as a clock source. The PLL settling time is 100 μs.
3.7.15.3 Reset And Wake-Up Timer
Reset has two sources on the LPC2148: the RESET pin and watchdog reset. The RESET pin is a Schmitt trigger input pin with an additional glitch filter. The other issue faced with the accidents is that the cause of the accident is unknown such that police enquiry is not done completely as the exact causes are unknown and it misleads to improper investigation. These problems can be rectified using Wireless Black Box using MEMS Accelerometer.
This project is to develop a wireless black box using MEMS accelerometer and GPS tracking system for accidental monitoring. Mems accelerometer is used to detect the motion of the object that is the sensory movements of the object are detected. Based on the sensory movements if any unusual accelerations occur it detects that an accident has occurred and this information is detected with position using a GPS Module and messages are sent to the saved family members and other emergency members using GSM module.GPS module is used to detect the location and position of the object using coordinates that is using x-axis ,y-axis and z-axis. GSM module is used to send the located position of the accident to the saved numbers of the family members and other numbers using the module .We use LPC 2148 microcontroller for the detection ,position and message sending as the information is controlled by the LPC 2148 microcontroller for the GPS,GSM and MEMS Accelerometer. This project also involves playback recording using a playback recorder such that for a duration of one minute during the occurrence of the accident the voices of the accident victims are recorded such that the exact cause of the accident can be known so that it will also be helpful for the police Investigation. Therefore these services which are included in the project have a great impact on accident detection ,location and also voice recording are very much helpful accidental monitoring of vehicles.In the existing system this accident detection and monitoring of the vehicles is mainly used for the airplanes such that most of the accident detections and occurrence are known using this system .These are mostly used for the higher end vehicles because of its higher cost .The implementation of Blck Box using Mems Accelerometer is very useful in tracking of vehicles and accident detection of vehicles and also playback recording.In this project we are detecting the position of the accident vehicle using the Mems Accelerometer motion ,that is due to the unusual accelerations of the MEMS Accelerometer the position of the vehicle is detected using GPS module and the accident location is sent to the family members using GSM module and the whole is controlled by LPC2148 microcontroller to perform all these actions. Another feature added in this project is that a playback recorder is introduced so that the voices are detected during the occurrence of the accident. Above all even the cost factor is also reduced such that this can be introduced in all vehicles for accident detection By using GSM we can send the message to family members, emergency medical service and nearest hospital.
3.7.15.4 Brownout Detector
The LPC2148 include 2-stage monitoring of the voltage on the VDD pins. If this voltage falls below 2.9 V, the BOD asserts an interrupt signal to the VIC. reading dedicated register. The second stage of low voltage detection asserts reset to inactivate the LPC2148 when the voltage on the VDD pins falls below 2.6 V. This reset prevents alteration of the flash as operation of the various elements of the chip would otherwise become unreliable due to low voltage. The BOD circuit maintains this reset down below 1 V, at which point the POR circuitry maintains the overall reset. Both the 2.9 V and 2.6 V thresholds include some hysteresis. In normaloperation, this hysteresis allows the 2.9V detection to reliably interrupt, or a regularly-executed event loop to sense the condition.
3.8 POWER CONTROL
The LPC2148 supports two reduced power modes: Idle mode and Power-down mode. In Idle mode, execution of instructions is suspended until either a reset or interrupt occurs. Peripheral functions continue operation during idle mode and may generate interrupts to cause the processor to resume execution. Idle mode eliminates power used by the processor itself, memory systems and related controllers, and internal buses that are able to function without clocks. Since all dynamic operation of the chip is suspended, Power-down mode reduces chip power consumption to nearly zero. Selecting an external 32 kHz clock instead of the PCLK as a clock-source for the on-chip RTC will enable the microcontroller to have the RTC active during Power-down mode. Power-down current is increased with RTC active. However, it is significantly lower than in Idle mode. A Power Control for Peripherals feature allows individual peripherals to be turned off if they are not needed in the application, resulting in additional power savings during active and idle mode.
3.8.1 VPB BUS
.8.2 EMULATION AND DEBUGGING
The LPC2148 support emulation and debugging via a JTAG serial port. A trace port allows tracing program execution. Debugging and trace functions are multiplexed only with GPIOs on Port 1. This means that all communication, timer and interface peripherals residing on Port 0 are available during the development and debugging phase as they are when the application is run in the embedded system itself
3.8.3 EMBEDDED ICE:
Standard ARM Embedded ICE logic provides on-chip debug support. The debugging of the target system requires a host computer running the debugger software and an Embedded ICE protocol convertor. Embedded ICE protocol convertor converts the remote debug protocol commands to the JTAG data needed to access the ARM core. The ARM core has a Debug Communication Channel (DCC) function built-in. The DCC allows a program running on the target to communicate with the host debugger or another separate host without stopping the program flow or even entering the debug state. The DCC is accessed as a co-processor 14 by the program running on the ARM7 TDMI-S core. The DCC allows the JTAG port to be used for sending and receiving data without affecting the normal program.
3.8.4 REAL MONITOR
Real Monitor is a configurable software module, developed by ARM Inc., which enables real-time debug. It is a lightweight debug monitor that runs in the background while users debug their foreground application. It communicates with the host using the DCC, which is present in the Embedded ICE logic. The LPC2148 contain a specific configuration of Real Monitor software programmed into the on-chip flash memory.
Because Hardware system of LPC2148 includes the necessary devices within only one MCU such as USB, ADC, DAC, Timer/Counter, PWM, Capture, I2C, SPI, UART, and etc.
3.8.5 Pulse Width Modulation (PWM)
Pulse-width modulation (PWM) is a commonly used technique for controlling power to an electrical device, made practical by modern electronic power switches. The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast pace. The longer the switch is on compared to the off periods, the higher the power supplied to the load is and current, is thus in both cases close to zero. PWM works also well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle. PWM has also been used in certain communication systems where its duty cycle has been used to convey information over a communications channel.