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Intelligent Ambulance for City Traffic Police
1. INTRODUCTION
In recent years due to globalization there has been a sudden rise
in the demand for automated traffic control systems especially in urban
areas. This requires an adaptive method actuated by vehicles that
adopts logic programming to model and solve the decision problems
associated with traffic control. Such a method can be applied with
success to urban intersections with high levels of traffic where many
different and unpredictable events contribute to large fluctuations in
the number of vehicles that use the intersection.
The term Intelligent Traffic Control has been adopted to address
the latest generation of traffic control methods, that deploy
sophisticated modelling and optimisation tools to try and meet the
demand for a more efficient and effective way to manage the
movements of a large number of vehicles and easy movement of
special vehicles viz. VIP vehicles, Ambulances etc.
In practice, there are various types of traffic control systems that
are used to regulate traffic. For example, use of counters and timers to
control the traffic lights. This system however does not control the
traffic efficiently due to the ever increasing congestion of traffic.
Here the signal phases and cycle length are predetermined using
historical data; the time period of green light is predetermined and it
continues to be the same throughout the day, if no sensory input is
received. In our case the predetermined time for green light is 5
seconds. The system deals with the signal phase lengths that are
adjusted in response to traffic flow, as registered by the actuation of
vehicle and/or pedestrian detectors; if a sensory output is received by
the controller, it adjusts the time period of green light for the next road.
Suppose we are using only the output from the sensors then the
drawback is that suppose in a low congested road an ambulance or a
high priority vehicle comes it will not be signalled unless and until the
congestion is avoided so to deal with this situation we are planning to in
incorporate RFID modules which will prioritize the signals based on the
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traffic for only important vehicles Our proposed traffic control system
has been designed for a congested, single intersection of an urban
area. Traffic detection is carried out by various obstacle sensors that
continuously provide information on the volume of traffic on each lane
and the RFID's that are mounted on the special vehicles.
1.1 Specification:
Microcontroller P89V51RD2 [8051]
Sensors IR Modulation sensors
Access Mechanism RFID + 2 Tags
Communication Protocol RS232
Display System LEDs
OS Platform Linux, Windows
Table 1.1 – Specifications of Intelligent Traffic Controller
1.2 Block diagram
Figure 1.1 – Block Diagram of Intelligent Traffic control
2. THE MICROCONTROLLER
The P89V51RB2/RC2/RD2 are 80C51 microcontrollers with
16/32/64 kB Flash and 1024 bytes of data RAM. A key feature of the
P89V51RB2/RC2/RD2 is its X2 mode option. The design engineer can
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OBSTACLE SENSOR
LED
MICRO CONTROLLER
RFID
Intelligent Ambulance for City Traffic Police
choose to run the application with the conventional 80C51 clock rate
(12 clocks per machine cycle) or select the X2 mode (6 clocks per
machine cycle) to achieve twice the throughput at the same clock
frequency. Another way to benefit from this feature is to keep the same
performance by reducing the clock frequency by half, thus dramatically
reducing the EMI.The Flash program memory supports both parallel
programming and in serial In-System Programming (ISP). Parallel
programming mode offers gang-programming at high speed, reducing
programming costs and time to market. ISP allows a device to be
reprogrammed in the end product under software control. The
capability to field/update the application firmware makes a wide range
of applications possible. The P89V51RB2/RC2/RD2 is also In-Application
Programmable (IAP), allowing the Flash program memory to be
reconfigured even while the application is running.
2.1 Features
80C51 Central Processing Unit 5 V Operating voltage from 0 MHz to 40 MHz
16/32/64 kB of on-chip Flash user code memory with ISP (In-
System Programming) and IAP (In-Application Programming)
Supports 12-clock (default) or 6-clock mode selection via software
or ISP
SPI (Serial Peripheral Interface) and enhanced UART PCA (Programmable Counter Array) with PWM and
Capture/Compare functions Four 8-bit I/O ports with three high-current Port 1 pins (16 mA
each)
Three 16-bit timers/counters Programmable watchdog timer
Eight interrupt sources with four priority levels Second DPTR register Low EMI mode (ALE inhibit)
TTL- and CMOS-compatible logic levels Brown-out detection Low power modes
a. Power-down mode with external interrupt wake-upb. Idle mode
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DIP40, PLCC44 and TQFP44 packages
2.2 Block Diagram
Figure 2.1 – Block Diagram of Microcontroller
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2.3 Pinning Information
Figure 2.2 – Pin configuration
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Figure 2.3 – Another look of Pin Configuration
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2.4. Pin Multiplexing
As you will see in the following table, a no. of I/O pins have more
than one functions. i.e. a pin may be used as a simple input pin or a
serial communication receiver. This is called pin multiplexing. Using pin
multiplexing, a pin can be used for more than one function.
How is this possible? How can a pin be used for both purposes at
the same time? Well, it’s not. The pin is used for only one purpose at a
time. Pin multiplexing simply allows the pin to be used for different
applications at different times.
Thus, to use a pin as an input or a serial receiver, we just have to
initialize the pin by configuring the specific register.
But why to make it so complex? Why not just have a single pin for
input port and another as a serial receiver? As you go through the table
below, you will find that some of the pins satisfy as many as 3
functions. To replace 3 pins for every such pin will increase the pin
count dramatically. To accommodate all the pins, the size of the IC will
increase. Ultimately, you will end up with an IC as big as your palm, if
not more!
Hence, pin multiplexing helps to reduce the size of the IC without
compromising in the features of the microcontroller.
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2.5 Pin Description:
SYMBOL
DESCRIPTION
P0.0
to
P0.7
Port 0: Port 0 is an 8-bit open drain bi-directional I/O port. i.e. we can program the Port P0 to use its pins either as Inputs or as Outputs. To use these port pins as inputs, external pull up resistors should be connected. The need of pull up resistors is explained later. Pull up resistors are not essential for operating P0 as an output port.
P1.0
to
P1.7
Port 1: Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 pins are pulled high by the internal pull-ups when ‘1’s are written to them and can be used as inputs in this state. Apart from general purpose I/O Ports, P1 also has the following alternative functions.
P1.0T2: Counter input to Timer/Counter 2 or Clock-output from
Timer/Counter 2
P1.1 T2EX: Timer/Counter 2 capture/reload trigger and direction control
P1.2ECI: External clock input. This signal is the external clock input for the
PCA
P1.3CEX0: Capture/compare external I/O for PCA Module 0. Each capture/compare module connects to a Port 1 pin for external I/O. When not used by the PCA, this pin can handle standard I/O.
P1.4SS: Slave port select input for SPI
CEX1: Capture/compare external I/O for PCA Module 1
P1.5MOSI: Master Output Slave Input for SPI
CEX2: Capture/compare external I/O for PCA Module 2
P1.6MISO: Master Input Slave Output for SPI
CEX3: Capture/compare external I/O for PCA Module 3
P1.7SCK: Master Output Slave Input for SPI
CEX4: Capture/compare external I/O for PCA Module 4
P2.0
to
P2.7
Port 2: Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. Port 2 pins are pulled HIGH by the internal pull-ups when ‘1’s are written to them and can be used as inputs in this state. . Apart from general purpose I/O Ports, P2 also has the following alternative functions.
P3.0
to
P3.7
Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins are pulled HIGH by the internal pull-ups when ‘1’s are written to them and can be used as inputs in this state. . Apart from general purpose I/O Ports, P3 also has the following alternative
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functions.P3.0 RXD: serial input port
P3.1 TXD: serial output port
P3.2 INT0: external interrupt 0 input
P3.3 INT1: external interrupt 1 input
P3.4 T0: external count input to Timer/Counter 0
P3.5 T1: external count input to Timer/Counter 1
P3.6 WR: external data memory write strobe
P3.7 RD: external data memory read strobe
Program Store Enable: PSEN is the read strobe for external program memory. When the device is executing from internal program memory, PSEN is inactive (HIGH). When the device is executing code from external program memory, PSEN is activated twice each machine cycle.
RST
Reset: While the oscillator is running, a HIGH logic state on this pin for two machine cycles will reset the device. If the PSEN pin is driven by a HIGH-to-LOW input transition while the RST input pin is held HIGH, the device will enter the external host mode, otherwise the device will enter the normal operation mode.External Access Enable: EA must be connected to VSS in order to
enable the device to fetch code from the external program memory.
EA must be strapped to VDD for internal program execution.
Address Latch Enable: ALE is used during accessing an external memory. This pin is also the programming pulse input (PROG) for flash programming.
XTAL
1
Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock generator circuits.
XTAL
2
Crystal 2: Output from the inverting oscillator amplifier.
VDD Power supply
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VSS Ground
Table 2.1 – Pin Details
2.6 Pull Up Resistors
Pull up resistors are used on the input side so that the input pins
are at an expected logic level even if they are disconnected from the
input switches. If Pull Up resistors are not used, the voltage level at the
input pin will be floating in such a case and hence the outcome of the
circuit is unpredictable.
Consider the following circuit:
/ ------- _____/ -------| |--- | ---| |--- | ---| |--- \ / ------- GND
Here, a switch is connected at the input pin of a microcontroller.
Note the absence of a pull up resistor.
When the switch is closed, the pin is directly grounded and the
input pin reads a logic level 0. Thus logic level 0 should indicate that
the switch is closed. Now consider when the switch is open. The input
pin is not connected to anything else, hence the pin in open. Thus the
input pin is said to be kept floating. i.e. the voltage at the pin may vary
from 0 V to 5V randomly. Thus we cannot be sure every time that when
the logic at pin is 0, it is because of the closed switch or the floating
voltage.
Hence this circuit is not appropriate.
Now consider the circuit below:
VCC
/ \ | | / | ------- _____/ -------| |--- | ---| |---
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| ---| |--- \ / ------- GND
This circuit will eliminate our problem of floating pin. It is obvious
that when the pin is open, the voltage at the input pin is Vcc. But now
imagine what will happen if the switch is closed. What do you think will
the voltage be at the input pin? You don’t have the time to calculate
that! You have shorted Vcc and ground of your Power Supply! This is a
very wrong method to eliminate our original problem of floating
voltage.
Now see what’s happening here:
VCC
/ \ | | \ / Pull-up resistor \ | | / | ------- _____/ -------| |--- | ---| |--- | ---| |--- \ / ------- GND
When the switch is closed, the pin is directly connected to ground
and reads logic level 0. When the switch is opened, the pin is connected
to Vcc through a high value resistor; hence it reads a logic value 1.
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Thus, the use of pull up resistor has solved our problem. Note that
a high value pull up resistor must be used to limit the current flow to
ground when the switch is closed.
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3. 8051 TIMER/COUNTER PROGRAMMING
P89V51RD2 has 3 timers: T0, T1 and T2.They can be used as
timers or event counters. Here we’ll discuss the timers’ registers and
then show how to program the timers.
3.1 Timers
3.1.1 TIMER 0:
The 16-bit register of timer 0 is accessed as a low byte and high
byte. The low byte register is called TL0 and the high byte register is
referred to as TH0. These register can be addressed like any other
registers, such as A, B, R0, R1 etc. The mode of Timer 0 is set in the
TMOD register and it is controlled by the TCON register
.
3.1.2 TIMER 1:
Timer 1 is also 16 bits, and its 16-bit register is split into 2 bytes,
referred to as TL1 and TH1. These registers are accessible in the same
way as registers of Timer 0. The mode of Timer 1 is set in the TMOD
register and it is controlled by the TCON register
.
3.1.3 TIMER 2:
Timer 2 is a 16-bit Timer/Counter, which can operate as either an
event timer or an event counter, as selected by C/T2 in the special
function register T2CON. Timer 2 has four operating modes: Capture,
Auto-reload (up or down counting), Clock-out, and Baud Rate Generator,
which are selected using T2CON and T2MOD
3.2 TMOD (timer mode) RegisterBoth Timers 0 and 1 use the same register, called TMOD, to set
various timer operation modes. TMOD is an 8-bit register in which the
lower 4 bits are set aside for Timer 0 and upper 4 bits for Timer1. In
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each case, the lower 2 bits are used to set the timer mode and upper 2
bits are used to set the operation. These options are discussed next.
Table 3.1 - TMOD Register
3.2.1 M1, M0
M0 and M1 select the timer mode. There are 4 modes: 0, 1, 2 and
3.
Mode 0 is a 13 bit timer, mode 1 is a 16 bit timer, mode 2 is an 8 bit timer and mode 3 is used as a split timing mode. We will concentrate on modes 1 and 2 since they are the ones used more widely.
3.2.2 C/T (counter /timer)
This bit is used to decide whether the timer is used as a delay
generator or an event counter. If C/T =0, it is used as a timer for time
delay generation. The clock source for time delay is the crystal
frequency of the 8051.
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3.2.3 Clock source for timer
As you know, every timer needs a clock pulse to tick. What is the
source of the clock pulse for the 8051 timers? If C/T= 0, the crystal
frequency attached to the 8051 is the source of the clock of the timer.
The frequency for the timer is always 1/12th of the frequency of the
crystal attached to the 8051.
3.2.4 GATE
Every timer has a means of starting and stopping. The timers in
the 8051 can be started by both, hardware and software means. The
start and stop of the timer are controlled by means of software by the
TR (timer start) bits TR0 and TR1. This is achieved by setting and
clearing the TR bit. This starts and stops the timers as long as GATE=0.
The hardware way of starting and stopping the timer by an external
source is achieved by making GATE=1 in the TMOD register. For the
time being, we will consider only the software control of timers.
3.2.5 16-bit Time Mode (mode 1)
Timer mode "1" is a 16-bit timer. This is a very commonly used
mode.
TLx is incremented from 0 to 255. When TLx is incremented from 255, it
resets to 0 and causes THx to be incremented by 1. Since this is a full
16-bit timer, the timer may contain up to 65536 distinct values. If you
set a 16-bit timer to 0, it will overflow back to 0 after 65,536 machine
cycles.
3.2.6 8-bit Time Mode (mode 2)
Timer mode "2" is an 8-bit auto-reload mode. When a timer is in
mode 2, THx holds the "reload value" and TLx is the timer itself. Thus,
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TLx starts counting up. When TLx reaches 255 and is subsequently
incremented, instead of resetting to 0 (as in the case of modes 0 and
1), it will be reset to the value stored in THx.
3.2.7 Initialization of Timers:Following steps are to be followed to initialize and operate a timer in any mode:
1. Load TMOD value appropriately to specify the timer used, mode of timer, hardware/software control and operation (counter or timer)
2. Load TLx and THx according to the mode selected and the time delay desired.
3. Start the timer. ( Set TRx bit)
4. Keep monitoring the timer overflow flag (TFx) in the TCON register to see if it is raised. Get out of the loop when TFx becomes high.
5. Stop the timer. (Clear TRx bit)
Example:
Write a program to generate a square wave of frequency 1Khz at
the pin P1.1. Assume a crystal of 11.0592 Mhz Frequency. In8051 one
instruction cycle has 12 states. Therefore, the frequency of timer is
11.0592 Mhz /12 = 921.6 KHz. Therefore the time period of each count
will be 1/921.6 = 0.001085 mS = 1.085 microseconds.
For a square wave of 1 Khz, High time=Low time.
Also, High Time + Low Time = (1/1Khz) = 1000 microseconds
Therefore High time = Low time = 500 microseconds.
Now, our problem is simplified. All we have to do is wait for a time
period of 500 microseconds, and then toggle the pin P1_1.
To wait for 500 microseconds, we have to count up to 500/1.085
= 461 (approx).
Now looking at all the available modes, we see that the 16 Bit timer
mode is best suited for this application.
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(461)D = (01CD)H thus to initialize the timers, we have to load 01 in TH0 and CD in TL0. Given below is the solution program:
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#include<p89v51rd2.h> //include device file
void delay(); //declare functionvoid main()
{
delay(); //call delay
while(1) //do continuously
{
P1_1=~P1_1; //toggle P1_1delay(); //wait for 500 microseconds
}
}
void delay()
{
TMOD= 0x01; // select timer 0 in mode 1 (16 Bit)
TH0=0x01; // enter count for 500 microsecondsTL0= 0xCD; // “
TR0=1; //start timer 0
while(TF0==0) ; // wait for timer 0 overflow flag to be setTR0=0; //stop timer 0}
3.2.8 Counter Programming
Recall from last section that C/T bit in the TMOD register decides
the source of the clock for the timer. If C/T=0, the timer gets pulses
from the crystal. In contrast, when C/T=1, the counter counts up as
pulses are fed from pins 14 and 15. These pins are called T0 (timer 0
input) and T1 (timer 1 input).
Thus pulses coming from these pins are counted in the TLx and
THx registers according to the mode selected.
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3.2.9 Counter Operation
The counters have been included on the chip to relieve the
processor of timing and counting chores. When the program wishes to
count a certain number of internal pulses or external events, a number
is placed in one of the counters. The counter increments from the initial
number to the maximum and then rolls over to zero on the final pulse
and also set a timer flag. The flag condition may be tested by an
instruction to tell the program that the count has been accomplished.
Observe the following chart:
Figure 3.1 –Flow chart of Counter
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3.3 TCON (timer control) Register
Timers 1 and 0 are controlled using the upper 4 bits of the TCON
register. The lower 4 bits are used for setting interrupt function and will
be discussed later. The TRx bits (TR0 and TR1) are used to start and
stop the timers by software. The TFx bits (TF0 and TF1) are used to
monitor the status of the timers.
BIT 7 6 5 4 3 2 1 0
NAME TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0
Figure 3.2 – Block of TCON Register
3.4 8051 INTERRUPTS PROGRAMMINGThere are two ways to monitor the status of an ongoing process
or an external event: interrupts or polling:
3.4.1 Interrupts If process in question (or external event) interrupts the
microcontroller, asking it to execute a different program before carrying
out the original program, we say an interrupt has occurred.
The process can be timer operation or serial data transfer.
The external event can be recognized by 2 pins on the 8051.
And the “different program” id called the Interrupt Service Routine (ISR)
3.4.2 Polling
If a microcontroller keeps monitoring the status flags or inputs
pins continuously until a state change occurs and then branches off to
perform the rest of the program, the microcontroller is said to be polling
for the flags (or inputs)
Needless to say, using interrupts can result in faster and
simultaneous operation of functions.
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The P89V51RD2 has the following 8 different interrupts:
Brown Out External Interrupts 0 and 1 Timer Interrupts 0, 1 and 2 Serial/SPI interrupt PCA
<
3.4.3 The IEN0 and IEN1 (Interrupt Enable) Registers
By default at power up, all interrupts are disabled. This means
that even if, for example, the TF0 bit is set, the 8051 will not execute
the interrupt. Your program must specifically tell the 8051 that it wishes
to enable interrupts and specifically which interrupts it wishes to
enable.
Your program may enable and disable interrupts by modifying the
IEN0 and IEN1 SFR. Note that the EA bit in IEN0 should be enabled for
any interrupt to operate. If EA is cleared, none of the interrupts will be
activated irrespective of the status of other bits in IEN0 and IEN1.
IEN0:
IEN1:
Table 3.2 – Function of IEN0 and IEN1
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3.4.4 What Happens When an Interrupt Occurs?
When an interrupt is triggered, the following actions are taken
automatically by the microcontroller:
The current Program Address is saved.
In the case of Timer and External interrupts, the corresponding
interrupt flag is cleared.
Program execution transfers to the corresponding Interrupt
Service Routine address.
The Interrupt Service Routine executes.
Take special note of the 2nd step: If the interrupt being handled is a
Timer or External interrupt, the microcontroller automatically clears the
interrupt flag before passing control to your interrupt handler routine.
This means it is not necessary that you clear the bit in your code.
3.4.5 What Happens When an Interrupt Ends?
An interrupt ends when your program executes the “Return from
Interrupt” instruction. When the RETI instruction is executed the
following actions are taken by the microcontroller:
The saved Program Address is restored.
Normal program execution is resumed.
3.5. PROGRAMMING TIMER INTERRUPTS
Before, we considered the operation of timers using the polling
method. Now we will do the same using Interrupts.
To initialize a timer interrupt, the corresponding bits in the IEN0
register should be set.
Then we go about initializing the timer as described in the section
above.
Start the timer. When the timer rolls over from FFFF to 0000 (or FF to 00
in the 8 bit mode), the TFx flag is set. As soon as the TFx flag is set,
interrupt occurs and the program control is shifted to ISR.
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After the ISR is executed, the TFx flag is cleared and program flow
is returned to the original program.
Example: Write a program to create a square wave of frequency 1Khz
on pin P0.1. Simultaneously receive the data at P1 and send it to P2.
Program:#include<p89v51rd2.h>
void timer 0() interrupt 2 //interrupt service routine
{P0_1=~P0_1; //toggle P0_1
TR0=0; //stop timer 0}
void main()
{
IEN0=0x82; //enable interrupt for timer 0
delay(); //initialize timers and wait for 500
microseconds
while(1) //do continuously{
P2=P1; // receive data from P1 and send it to P2
}
}
void delay()
{TMOD=0x01; //select timer 0 in 16 bit mode
TH0=0x01; //load count
TL0=0xCD; // “
TR0=1; //start timer 0
}
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3.6 PROGRAMMING EXTERNAL INTERRUPTS
To initialize an external interrupt, the corresponding bits in the
IEN0 register should be set. The type of interrupt (low level/ High to
Low edge) is determined by setting to IEx bits in the TCON register.
(IEx=0: Low Level Interrupt, IEx=1: H-L Transition Interrupt)
Whenever the appropriate signal is received on the input pins,
(P3.2=Ext Int. 0, P3.3= Ext Int. 1), interrupt occurs and the program
control is shifted to ISR.
After the ISR is executed, the program flow is returned to the original
program.
The only thing that differentiates an ISR (Interrupt Service
Routine) from a normal function is the syntax in which an ISR is defined.
The syntax for defining an interrupt is as shown void ISR Name(void)
interrupt x Eg: void TIMER0_OVF(void) interrupt 1
x Interrupt0 Ext. Interrupt 0 (INT0)1 Timer 0 Overflow2 Ext. Interrupt 1 (INT1)3 Timer 1 Overflow4 UART5 T2
Example on using timer interrupts
This code is for an LED blinking program using timers. The LEDs connected on P3_0, P3_6 and P3_7 will blink.
#include
unsigned char i=0,j=0,k=0;
void timer2_ovf() interrupt 5 //Timer 2 ISR{k++;if(k==50){
k=0;RXD=!RXD;}TF2=0; //Reset overflow flag
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}
void timer0_ovf(void) interrupt 1 //Timer 0 ISR{i++;if(i==50){i=0;RD=!RD;}
}
void timer1_ovf(void) interrupt 3 //Timer 1 ISR{j++;if(j==50){j=0;WR=!WR;}
}
void main(void){TMOD=0×11; //Set timer 0 and 1 in mode 1T2CON=0×04; //Start timer 2 in 16 bit modeET1=1; //Enable Timer 1 overflow interruptET0=1; //Enable Timer 0 overflow interruptET2=1; //Enable Timer 2 overflow interruptTR0=1; //Timer 0 runTR1=1; //Timer 1 runEA=1; //Global Interrupt enablewhile(1){}
}
Example on using external interruptsIn this you can see that the LEDs connected on the RD and WR (i.e. P3_6 and P3_7) pins glow when there is an external interrupt(i.e. switch is pressed)
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#include
void ext_int0(void) interrupt 0 //INT0 ISR{RD=0;}void ext_int1(void) interrupt 2 //INT1 ISR{WR=0;}void main(void){TCON=0×05; //Set interrupt type. Edge triggered in this caseEX1=1; //Enable external interrupt 1EX0=1; //Enable external interrupt 0EA=1; //Global interrupt enablewhile(1){}
}
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4. OBSTACLE SENSOR
4.1 Sensor
Sensors are the device that responds to a physical stimulus (heat,
light, sound, pressure, motion, flow, and so on), and produces a
measurable corresponding electrical signal
4.2 Sensor Technology
So far, we have considered mainly the nature and characteristics
of EM radiation in terms of sources and behavior when interacting with
materials and objects. It was stated that the bulk of the radiation
sensed is either reflected or emitted from the target, generally through
air until it is monitored by a sensor. The subject of what sensors consist
of and how they perform (operate) is important and wide ranging
Most remote sensing instruments (sensors) are designed to
measure photons. The fundamental principle underlying sensor
operation centers on what happens in a critical component - the
detector. This is the concept of the photoelectric effect (for which Albert
Einstein, who first explained it in detail, won his Nobel Prize [not for
Relativity which was a much greater achievement]; his discovery was,
however, a key step in the development of quantum physics). This,
simply stated, says that there will be an emission of negative particles
(electrons) when a negatively charged plate of some appropriate light-
sensitive material is subjected to a beam of photons. The electrons can
then be made to flow from the plate, collected, and counted as a signal.
A key point: The magnitude of the electric current produced (number of
photoelectrons per unit time) is directly proportional to the light
intensity. Thus, changes in the electric current can be used to measure
changes in the photons (numbers; intensity) that strike the plate
(detector) during a given time interval. The kinetic energy of the
released photoelectrons varies with frequency (or wavelength) of the
impinging radiation.
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But, different materials undergo photoelectric effect release of
electrons over different wavelength intervals; each has a threshold
wavelength at which the phenomenon begins and a longer wavelength
at which it ceases.
4.3 Obstacle sensor
Obstacle sensor is a effective IR proximity sensor built with the
TSOP 1738 module. The TSOP module is commonly found at the
receiving end of an IR remote control system; e.g., in TVs, CD players
etc. These modules require the incoming data to be modulated at a
particular frequency and would ignore any other IR signals. There are
various sources of IR sensors and our receiver must receive IR rays only
from our source and ignore other IR Rays. It is also immune to ambient
IR light, so one can easily use these sensors outdoors or under heavily
lit conditions.
Such modules are available for different carrier frequencies from 30 kHz
to 56 kHz.
In this particular proximity sensor, we will be generating a constant
stream of square wave signal using IC555 centered at 38 kHz and would
use it to drive an IR led. So whenever this signal bounces off the
obstacles, the receiver would detect it and change its output. Since the
TSOP 1738 module works in the active-low configuration, its output
would normally remain high and would go low when it detects the signal
(the obstacle)
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4.3.1 Schematic of TSOP sensor
Figure 4.1 – Schematic of TSOP
4.3.2 LM555 Timer
The LM555 is a highly stable device for generating accurate time
delays or oscillation. Additional terminals are provided for triggering or
resetting if desired. In the time delay mode of operation, the time is
precisely controlled by one external resistor and capacitor. For astable
operation as an oscillator, the free running frequency and duty cycle
are accurately controlled with two external resistors and one capacitor.
The circuit may be triggered and reset on falling waveforms, and the
output circuit can source or sink up to 200mA or drive
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Figure 4.2 – LM 555 timer
4.3.3 Calculation for 555 Timer
This calculation is designed to give timing values for the 555
timer, based on the control capacitance and resistance. This particular
configuration is for an astable square wave calculation. The positive
output is high for T(h) seconds based on this formula:
Time High (secs) = 0.693 * (R1 + R2) * C.
The negative output is low for T(l) seconds based on this formula:
Time Low (secs) =0.693 * R2 * C
The frequency is derived by the formula:
Frequency = 1.44 / ((R1 + R2 + R2) * C)
The duty cycle percentage is the relationship of the high time to the
overall cycle time and is derived by the formula:
DCP = (T(h) / (T(h) + T(l))) * 100
Where resistance is in ohms and capacitance is in farads. Enter
the capacitance in farads (not microfarads) and the resistance in ohms
for each resistor. Click on Calculate to return the time high in seconds,
the time low in seconds, the duty cycle percentage and the frequency
in hertz.
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5. RFID
5.1 LF RFID MODULE
The DT125R series RFID Proximity OEM Reader Module has a
built-inantenna in minimized form factor. It is designed to work on the
industry standard carrier frequency of 125 kHz.
This LF reader module with an internal or an external antenna
facilitates communication with Read-Only transponders—type UNIQUE
or TK5530 via the air interface. The tag data is sent to the host systems
via the wired communication interface with a protocol selected from the
module pinout.
The LF DT125R module is best suited for applications in Access
Control,Time and Attendance, Asset Management, Handheld Readers,
Immobilizers, and other RFID enabled applications.
5.2 Features
Selectable UART or Wigand26
Plug-and-Play, needs +5V to become a reader
No repeat reads
LED/Beeper indicates tag reading operation
Excellent read performance without an external circuit
Compact size and cost-effective
A very efficient module for portable readers.
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5.3. Block Diagram
Figure 5.1 – Block diagram of RFID Module
The LF DT125R reader consists a RF front end interfaced with the
baseband processor that operates with +5V power supply. An antenna
is interfaced with the RF front end, and tuned at 125 kHz to detect a tag
(transponder) that comes in the vicinity of the reader field.
The data read from the tag by the front end is detected and
decoded by the base band processor and is then sent to the UART
interface.
The DT125R is designed for a reading range of 50 mm to 100 mm.
A LED and a beeper can be interfaced to the pin out to indicate the tag
read status.
DT125R has a built-in circuitry for noise reduction.
5.3.1 Data Transmission in ASCII Standard
Data read from the tag is Manchester encoded. The Manchester
encoded data is decoded to ASCII standard. Decoded data is sent to the
UART serial interface for wired communication with the host systems.
ASCII data format is shown below:
The 1byte (2 ASCII characters) Check sum is the “Exclusive OR” of
the 5 hex bytes (10 ASCII) Data characters.
It takes the full memory of the card from D00 to D93 and divides
this memory into 10 groups of 4 bits.
Group1= D00 to D03; Group2= D10 to D13 ……Group10= D90 to D93.
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The reader then takes the corresponding HEX value for each
group of 4 bits 0…FHEX. This HEX value is now taken as ASCII
characters and the reader transmits the
ASCII value.
STX (02h) DATA (10 ASCII) CHECK SUM (2 ASCII) CR LF ETX (03h)
5.3.2 Specifications:
Dimensions (LXBXH) mm 30x30x10
Frequency 125 kHz
Reading Distance >= 50 mm
Interface UART, Wiegand26
Antenna Built-in and External
Supply Voltage +5 V
Operating temperature 10°C to +50°C (-14°F to +122°F)
Tag Types Unique, TK5530
Output Format ASCII
Color Black
Table 5.1 – Specifications of RFID Module.
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Figure 5.2 – Dimension of RFID Module
5.3.3 Pin Number Description
PIN 1 1 LED/BEEPER
PIN 2 Data1
PIN 3 Data0
PIN 4 GND
PIN 5 TTL1 (TXD)
PIN 6 TTL0 (RXD)
PIN 7 NC
PIN 8 VCC
PIN 9 ANTENNA 1
PIN 10 ANTENNA 2
Table 5.2 – Pin Details
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Figure 5.3 – Bottom view of RFID Module
5.3.4 Schematic Diagram
Figure 5.4 – Schematic Diagram of RFID Module
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5.4 Applications
Applications of the RFID OEM LF DT125R Reader Module are
limited by the imagination of the designer because of the compact form
factor and low power consumption. Some of the common applications
for this module are:
Access control
Handheld readers
Asset management
Time and Attendance
Immobilizers
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6. LIGHT EMITTING DIODES
Traffic lights, also known as traffic signals, stop lights, traffic
lamps, stop-and-go lights, robots or semaphore, are signaling devices
positioned at road intersections, pedestrian crossings, and other
locations to control competing flows of traffic.
Traffic lights have been installed in most cities around the world
to control the flow of traffic. They assign the right of way to road users
by the use of lights in standard colors (Red - Amber - Green), using a
universal color code (and a precise sequence, for those who are color
blind). They are used at busy intersections to more evenly apportion
delay to the various users.
The most common traffic lights consist of a set of three lights:
red, yellow (officially amber), and green. When illuminated, the red light
indicates for vehicles facing the light to stop; the amber indicates
caution, either because lights are about to turn green or because lights
are about to turn red; and the green light to proceed, if it is safe to do
so.
There are many variations in the use and legislation of traffic lights,
depending on the customs of a country and the special needs of a
particular intersection. There may, for example, be special lights for
pedestrians, bicycles, buses, trams, etc; light sequences may differ; and
there may be special rules, or sets of lights, for traffic turning in a
particular direction. Complex intersections may use any combination of
these.
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6.1 Traffic Lights
Traffic lights can have several additional lights for filter turns or
bus lanes. This one in Warrington, also shows the distinctive red +
amber combination seen in the UK. It also shows the backing board and
white border used to increase the target value of the signal head.
Improved visibility of the signal head is achieved during the night by
using the retro-reflective white border
In many regions, traffic lights function differently or have different
displays depending on available technology, traffic patterns, or other
vehicles such as trolleys that also use the intersection. For example,
some fixtures feature a flashing green light or more than one arrow lit
at one time. An example of a flashing green light found in Canada, to
notify left turning drivers that they have the right of way and that the
opposing lanes will not be moving.
6.1.1 Three Set Lights
Figure 6.1 – Three set Lights
The universal standard is for the red to be above the green, and if
there is also amber it is placed in the middle. If the three-set lights are
mounted horizontally, the red will typically be to the left of the green.
The standards apply whether the country drives on the left or the right,
but the placement of the mountings on the road would be mirror
images of the other.
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Yellow
Green
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Each country has differing road rules, including how traffic lights
are to be interpreted. For example, in some countries, a flashing yellow
light means that a motorist may proceed with care if the road is clear,
giving way to pedestrians and to other road vehicles that may have
priority (essentially the same as arriving at a non-signalized intersection
and not facing a stop sign). A flashing red may be treated as a regular
stop sign.
6.2 Turning signals and rules
Figure 6.2 – Working of Traffic Lights
In some instances, traffic may turn left (in left-driving
jurisdictions) or right (in right-driving jurisdictions) after stopping at a
red light, providing they give way to the pedestrians and other vehicles.
In some cases which generally disallow this, a sign next to the traffic
light indicates that it is allowed at a particular intersection.
Conversely, jurisdictions which generally allow this might forbid it
at a particular intersection with a "no turn on red" sign, or might put a
green arrow to indicate specifically when a turn is allowed without
having to yield to pedestrians (this is usually when traffic from the
perpendicular street is making a turn onto one's street and thus no
pedestrians are allowed in the intersection anyway).
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Some jurisdictions allow turning on red in the opposite direction
(left in right-driving countries; right in left-driving countries) from a one-
way road onto another one-way road; some of these even allow these
turns from a two-way road onto a one-way road. Also differing is
whether a red arrow prohibits turns; some jurisdictions require a "no
turn on red" sign in these cases. A study in the State of Illinois (a right-
driving jurisdiction) concluded that allowing drivers to proceed straight
on red after stopping, at specially posted T-intersections where the
intersecting road went only left, was dangerous. Proceeding straight on
red at T-intersections where the intersecting road went only left was
once legal in Mainland China with right-hand traffic provided that such
movement would not interfere with other traffic, but when the Road
Traffic Safety Law of the People's Republic of China took effect on 1 May
2004, such movement was outlawed.[13]. In some other countries the
permission is indicated by a flashing amber arrow (cars do not have to
stop but must give way to other cars and pedestrians).
Another distinction is between intersections that have dedicated
signals for turning across the flow of opposing traffic and those that do
not. Such signals are called dedicated left-turn lights in the United
States and Canada (since opposing traffic is on the left). With dedicated
left turn signals, a left-pointing arrow turns green when traffic may turn
left without conflict, and turns red or disappears otherwise. Such a
signal is referred to as a "protected" signal if it has its own red phase; a
"permissive" signal does not have such a feature. Three standard
versions of the permissive signal exist: One version is a horizontal bar
with five lights - the green and yellow arrows are located between the
standard green and yellow lights. A vertical 5-light bar holds the arrows
underneath the standard green light (in this arrangement, the yellow
arrow is sometimes omitted, leaving only the green arrow below the
solid green light, or possibly an LED based device capable of showing
both green and yellow arrows within a single lamp housing).
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A third type is known as a "doghouse" or "cluster head" - a
vertical column with the two normal lights is on the right side of the
signal, a vertical column with the two arrows is located on the left, and
the normal red signal is in the middle above the two columns. Cluster
signals in Australia and New Zealand use six signals, the sixth being a
red arrow which can operate separately from the standard red light. In
a fourth type, sometimes seen at intersections in Ontario and Quebec,
Canada, there is no dedicated left-turn lamp per se. Instead, the normal
green lamp flashes rapidly, indicating permission to go straight as well
as make a left turn in front of opposing traffic, which is being held by a
steady red lamp. (This "advance green," or flashing green can be
somewhat startling and confusing to drivers not familiar with this
system. This also can cause confusion amongst visitors to British
Columbia, where a flashing green signal denotes a pedestrian
controlled intersection.[14]) Another interesting practice seen at least
in Ontario is that cars wishing to turn left that arrived after the left turn
signal ended can do so during the amber phase, as long as there is
enough time to make a safe turn.
A flashing amber arrow, which allows drivers to make left turns
after giving way to oncoming traffic, is becoming more widespread in
the United States, particularly in Oregon. In the normal sequence, a
protected green left-turn arrow will first change to a solid amber arrow
to indicate the end of the protected phase, then to a flashing amber
arrow, which remains flashing until the standard green light changes to
amber and red. In Oregon, the amber-flashing arrow is usually housed
in a separate light head from the steady amber arrow, in order to
provide a visible position change. These generally take the form of four
signal heads (green, amber, amber, red). On some newer signals,
notably in the city of Bend, the green and flashing amber arrows
emanate from the same light head through the use of a dual-color LED
array, while the solid amber arrow is mounted above it.
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Generally, a dedicated left-turn signal is illuminated at the
beginning of the green phase of the green-yellow-red-green cycle. This
allows left-turn traffic, which often consists of just a few cars, to vacate
the intersection quickly before giving priority to vehicles traveling
straight. This increases the throughput of left-turn traffic while reducing
the number of drivers, perhaps frustrated by long waits in heavy traffic
for opposing traffic to clear, attempting to make an illegal left turn on
red. If there is no left-turn signal, the law requires one to yield to
oncoming traffic and turn when the intersection is clear and it is safe to
do so. Nevertheless, it is increasingly and disturbingly common in at
least the U.S. to see drivers who do not yield in the absence of a
dedicated signal, cutting off traffic that has right-of-way and is starting
to head across the intersection.[citation needed]
In the U.S., many older inner-city and rural areas do not have
dedicated left-turn lights, while most newer suburban areas have them.
Such lights tend to decrease the overall efficiency of the intersection as
it becomes congested, although it makes intersections safer by
reducing the risk of head-on collisions and may even speed up through
traffic, but if a significant amount of traffic is turning, a dedicated turn
signal helps eliminate congestion.
Some intersections with protected-turn signals occasionally have what
is known as "yellow trap", "lag-trap", or "left turn trap" (in right-driving
countries). It occurs at intersections where vehicles are permitted to
make left turns on normal green lights. "Yellow trap" refers to situations
when left-turning drivers are trapped in the intersection with a red light,
while opposing traffic still has a green.
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For example, an intersection has dedicated left-turn signals for
traffic traveling north. The southbound traffic gets a red light so
northbound traffic can make a left turn, but the straight-through
northbound traffic continues to get a green light. A southbound driver
who had entered the intersection earlier will now be in a predicament,
since they have no idea whether traffic continuing straight for both
directions is becoming red, or just their direction. The driver will now
have to check the traffic light behind them, which is often impossible
from the viewing angle of a driver's seat. This can also happen when
emergency vehicles or railroads preempt normal signal operation. In
the United States, signs reading "Oncoming traffic has extended green"
or "Oncoming traffic may have extended green" must be posted at
intersections where the "yellow trap" condition exists.
Although motorcycles and scooters in most jurisdictions follow the
same traffic signal rules for left turns as do cars and trucks, some
places, such as Taiwan, have different rules. In these areas, it is not
permitted for such small and often hard-to-see vehicles to turn left in
front of oncoming traffic on certain high-volume roads when there is no
dedicated left-turn signal. Instead, in order to make a left turn, the rider
moves to the right side of the road, travels through the first half of the
intersection on green, then slows down and stops directly in front of the
line of cars on the driver's right waiting to travel across the intersection,
which are of course being held by a red light. There is often a white box
painted on the road in this location to indicate where the riders should
group. The rider turns the bike 90 degrees to the left from the original
direction of travel and proceeds along with the line of cars when the red
light turns green, completing the left turn. This procedure improves
safety because the rider never has to cross oncoming traffic, which is
particularly important given the much greater likelihood of injury when
a cycle is hit by a car or truck.
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This system (called a "hook-turn") is also used at many
intersections in the CBD of Melbourne, Australia, where both streets
carry tramways. This is done so right-turning vehicles (Australia drives
on the left) do not block the passage of trams. The system is being
extended to the suburbs.
At intersections where no turns are allowed from any direction, the
green light can be replaced with a green arrow pointing up.
6.3 Programming on LEDsIn 8051 LEDs can be connected to pins P3_0, P3_1, P3_6, and
P3_7. These pins have to be initialized as input ports or out put port. For
input initialization port is given as 1 and for out put port is given as 0.
Example:Write a program for blinking of an LED
#include<P89v51rd2.h>
void delay(unsigned char del);
void main()
{
while(1)
{
P3_0=0;
delay (20);
P3_0=1;
Delay (20);
}}void delay (unsigned char del){int i,j;for (i=0;i<1000;i++)for (j=0;j<del;j++);}
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7. ADVANTAGES & ISSUE RELATED TO INTELLIGENT AMBULANCE
7.1 Abstract Problem statement- Traffic congestion and tidal
flow management were recognized as major problems in modern urban
areas, which have caused much frustration and loss of man-hours.
In order to solve the problem an intelligent RFID traffic control has
been developed. It is intended to avoid the problems that usually arise
with conventional systems.
7.2 Pre-timed- where the signal phases and cycle length are
predetermined using historical data; the time period of green light is
predetermined and it continues to be the same throughout the day, if
no sensory input is received. In our case the predetermined time for
green light is 5 seconds.
7.3 Actuated- where the signal phase lengths are adjusted in
response to traffic flow, as registered by the actuation of vehicle and/or
pedestrian detectors; if a sensory output is received by the controller, it
adjusts the time period of green light for the next road. Suppose we are
using only the output from the sensors then the drawback is that
suppose in a low congested road an ambulance or a high priority
vehicle comes it will not be signaled unless and until the congestion is
avoided so to deal with this situation we are planning to in incorporate
RFID modules which will prioritize the signals based on the traffic on the
priority vehicles also.
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8. CONCLUSION
A system is useful to improve the traffic flow on the road as well
as at the intersections of the roads, which in turn reduce the traveling
time, fuel consumption, and emissions, by reducing the cross over time
required at each intersection and by preventing or relieving the
congestions on the roads. The method controls traffic of vehicles
running between the two intersections or signals. The system
establishes the intelligent interaction among every two adjacent traffic
signals which results in the helps in the formation of the collection of
vehicles crossing the next signal which in tern helps in optimum
utilization of the ON time or Green time of the traffic signals. The
system also provides the real-time, necessary and useful information to
drivers in order to cross the next intersection or signal in minimum time
without exceeding or crossing the maximum and the minimum speed
limits. The system also detects the vehicle congestions and resolves it
by adjusting the traffic flow and size of the vehicle collections,
accordingly by changing the ON times of the signals with the help of
intelligent interaction among the traffic signals. The ON time of the
traffic signal near the congestion area is increased and the increased
time helps to resume the traffic flow, as earlier. The increased amount
of time is adjusted from the ON time of the adjacent signals so that the
traffic flow in the other areas should be less affected.
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11. REFRENCES
8051 Microcontroller & Embedded Systems using assembly and C Languages.
Author : Muhammed Ali Mazidi, Janice Gillispie Mazidi. 2006.
8051 Microcontroller 4th Edition
Author : Mc Kenzie
8051 Microcontroller Hardware, Software & Interfacing
Author : 1) James W Stewart
2) Kai Z. Mico 1999.
RFID Hand Book: Fundamentals & Applications
Author : Klans Finkenzeller 2003.
RFID : Radio Frequency Identification
Author : Steven Shepherd 2005.
RFID Essentials
Author : Bill Glover
Himanshu Bhatt 2006.
Sensors & Actuators
Author : Elseiver 2001.
Optical Sensors
Author : Narayan Swami
Linear and Digital IC Application
Author: U.A. Bakshi
Digital Electronics & Logic Design
Author : B Somnath Nair
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WEBSITES:
http://www.Digant.com//
http://www.555 Timer tutorials.com//
//Wikipedia, the free encyclopedia//
http://www.alldata sheets.com//
http://www.Luminlabz.com//
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