With these 3, OS will understand the input given by us and perform the action to the corresponding input.
 
Example : when we press key 2 in the keyboard... event sequence will be like the below

In ubuntu,  (I wrote a c program to read the input even from device and the output is below)
Event: type 4 (Misc), code 4 (ScanCode), value 458783   [Conveying the event is scancode]
Event: type 1 (Key), code 3 (2), value 1                             [key 2 pressed]
Event: type 0 (Sync), code 0 (Sync), value 0                      [sync event]
Event: type 4 (Misc), code 4 (ScanCode), value 458783    [conveying the event is scancode]
Event: type 1 (Key), code 3 (2), value 0                             [key 2 release]
Event: type 0 (Sync), code 0 (Sync), value 0                      [sync event]

In andriod,
Event: type 1 (Key), code 3 (2), value 1                             [key 2 pressed]
Event: type 0 (Sync), code 0 (Sync), value 0                      [sync event]
Event: type 1 (Key), code 3 (2), value 0                             [key 2 release]
Event: type 0 (Sync), code 0 (Sync), value 0                      [sync event]

This is for pressing the key 2 once... This will be written into the device, OS will read it and perform the actions.

ok now...

getevent : will print the event written into the device.
syntax    : getevent device
example : getevent /dev/input/event0
output    :  In android, it didn't say the scancode... but all the inputs are handled as scancodes. output is,
0001 0003 00000001
0000 0000 00000000
0001 0003 00000000
0000 0000 00000000

sendevent : will allow us to give the input in the terminal.
syntax       : sendevent device type code value.
example    : for writing key 2 into the device.
shell@android:/ # sendevent dev/input/event0 0000 0000 00000000
shell@android:/ # sendevent dev/input/event0 0001 0003 00000001
shell@android:/ # sendevent dev/input/event0 0000 0000 00000000
shell@android:/ # sendevent dev/input/event0 0000 0000 00000000


P.S. : Remember the two points below,

1.  Run it in the android shell.
2.  Should have root permission.

hi friend,
since my final year project is about GPS-GSM based vehicle tracking and theft control.. i got a chance to learn about the GPS module working.. so i would like to share it with you all..


GLOBAL POSITIONING SYSTEM(GSP)

Our ancestors had to go to pretty extreme measures to keep from getting lost. They erected monumental landmarks, laboriously drafted detailed maps and learned to read the stars in the night sky.
But today a small device can guide us all through the world.. which is know as the GPS.. even the latest versions of mobile phones has inbuilt GPS module in it..

WHEN AND HOW GPS CAME:

The Global Positioning System (GPS) is actually a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). The U.S. military developed and implemented this satellite network as a military navigation system, but soon opened it up to everybody else.

A GPS receiver's job is to locate four or more of these satellites, figure out the distanc­e to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration. 


WORKING

2-D Trilateration

Imagine you are somewhere in the United States and you are TOTALLY lost -- for whatever reason, you have absolutely no clue where you are. You find a friendly local and ask, "Where am I?" He says, "You are 625 miles from Boise, Idaho."
This is a nice, hard fact, but it is not particularly useful by itself. You could be anywhere on a circle around Boise that has a radius of 625 miles, like this:

You ask somebody else where you are, and she says, "You are 690 miles from Minneapolis, Minnesota." Now you're getting somewhere. If you combine this information with the Boise information, you have two circles that intersect. You now know that you must be at one of these two intersection points, if you are 625 miles from Boise and 690 miles from Minneapolis.

If a third person tells you that you are 615 miles from Tucson, Arizona, you can eliminate one of the possibilities, because the third circle will only intersect with one of these points. You now know exactly where you are -- Denver, Colorado.

This same concept works in three-dimensional space, as well, but you're dealing with spheres instead of circles. In the next section, we'll look at this type of trilateration.

3-D Trilateration

Fundamentally, three-dimensional trilateration isn't much different from two-dimensional trilateration, but it's a little trickier to visualize. Imagine the radii from the previous examples going off in all directions. So instead of a series of circles, you get a series of spheres.
If you know you are 10 miles from satellite A in the sky, you could be anywhere on the surface of a huge, imaginary sphere with a 10-mile radius. If you also know you are 15 miles from satellite B, you can overlap the first sphere with another, larger sphere. The spheres intersect in a perfect circle. If you know the distance to a third satellite, you get a third sphere, which intersects with this circle at two points.
The Earth itself can act as a fourth sphere -- only one of the two possible points will actually be on the surface of the planet, so you can eliminate the one in space. Receivers generally look to four or more satellites, however, to improve accuracy and provide precise altitude information.
In order to make this simple calculation, then, the GPS receiver has to know two things:

• The location of at least three satellites above you
• The distance between you and each of those satellites

The GPS receiver figures both of these things out by analyzing high-frequency, low-power radio signals from the GPS satellites. Better units have multiple receivers, so they can pick up signals from several satellites simultaneously.
Radio waves are electromagnetic energy, which means they travel at the speed of light (about 186,000 miles per second, 300,000 km per second in a vacuum). The receiver can figure out how far the signal has traveled by timing how long it took the signal to arrive.

NOW LET WE SEE HOW THE GPS USE THIS TO CALCULATE OUR LOCATION

On the previous page, we saw that a GPS receiver calculates the distance to GPS satellites by timing a signal's journey from satellite to receiver. As it turns out, this is a fairly elaborate process.
At a particular time (let's say midnight), the satellite begins transmitting a long, digital pattern called a pseudo-random code. The receiver begins running the same digital pattern also exactly at midnight. When the satellite's signal reaches the receiver, its transmission of the pattern will lag a bit behind the receiver's playing of the pattern.
The length of the delay is equal to the signal's travel time. The receiver multiplies this time by the speed of light to determine how far the signal traveled. Assuming the signal traveled in a straight line, this is the distance from receiver to satellite.
In order to make this measurement, the receiver and satellite both need clocks that can be synchronized down to the nanosecond. To make a satellite positioning system using only synchronized clocks, you would need to have atomic clocks not only on all the satellites, but also in the receiver itself. But atomic clocks cost somewhere between $50,000 and $100,000, which makes them a just a bit too expensive for everyday consumer use.
The Global Positioning System has a clever, effective solution to this problem. Every satellite contains an expensive atomic clock, but the receiver itself uses an ordinary quartz clock, which it constantly resets. In a nutshell, the receiver looks at incoming signals from four or more satellites and gauges its own inaccuracy. In other words, there is only one value for the "current time" that the receiver can use. The correct time value will cause all of the signals that the receiver is receiving to align at a single point in space. That time value is the time value held by the atomic clocks in all of the satellites. So the receiver sets its clock to that time value, and it then has the same time value that all the atomic clocks in all of the satellites have. The GPS receiver gets atomic clock accuracy "for free."
When you measure the distance to four located satellites, you can draw four spheres that all intersect at one point. Three spheres will intersect even if your numbers are way off, but four spheres will not intersect at one point if you've measured incorrectly. Since the receiver makes all its distance measurements using its own built-in clock, the distances will all be proportionally incorrect.
The receiver can easily calculate the necessary adjustment that will cause the four spheres to intersect at one point. Based on this, it resets its clock to be in sync with the satellite's atomic clock. The receiver does this constantly whenever it's on, which means it is nearly as accurate as the expensive atomic clocks in the satellites.
In order for the distance information to be of any use, the receiver also has to know where the satellites actually are. This isn't particularly difficult because the satellites travel in very high and predictable orbits. The GPS receiver simply stores an almanac that tells it where every satellite should be at any given time. Things like the pull of the moon and the sun do change the satellites' orbits very slightly, but the Department of Defense constantly monitors their exact positions and transmits any adjustments to all GPS receivers as part of the satellites' signals.

Thus by these information and with above calculation, our device give us our location..

hi friends,
In Recent years,the LCD is finding widespread use replacing LEDs. everyone would like to have it in their project to attract the visitors. similarly we too had it in our project "Power On Coin", But we made a very small, tiny mistake while interfacing and we spend nearly a week to identify that problem. But, we learned many things about LCDs in that week, that's here
INTERFACING OF LCD
 All LCD will have minimum of 14 pins, some may have few more for back LED lights. knowledge of these 14 pins is enough to interface LCD. let we have a look at those 14 pins.

 









VSS:ground pin     VDD:+5v supply pin

VEE:contrast pin, by adjusting the supply to this pin we can get clarity in the display.
 NOTE: never give full 5V supply, vary it with a variable resistor(pot:10k)
RS: this register will say the LCD whether the information is command or data.
we would like to control the cursor in the display like clearing, moving the cursor in the display, entry mode, etc. this could be done through passing command by Rs=0->we can inform the LCD the information is command. respectively command words and codes are shown.
while we are passing data we should have Rs=1.
R/W:we are suppose to inform the LCD, whether the information is to be read or written on the LCD. this pin will do that work.
R/W=1->read mode
R/w=0->write mode
ENABLE PIN:very important pin of all, only when pass high to low signal to this pin, the command/data will be latched into LCD. But should have at least 450ns gap between setting and clearing this pin. because the micro controller may be working at MHz but our LCD will be working at KHz . so, we need to apply some delay else the date will not be proper.
E line is negative edge triggered- to write
E line is positive edge triggered- to read

D7-D0:information should be sent/received only through pin only this is data pin. ASCII key values of the corresponding character or command should be alone sent/received through this pin.
these are those 14 pins.
WORKING:

• First we should configure the LCD,so we need to pass the command code. Don't send all, send only which are required.

Load D7-D0 with command code
Rs=0; to inform it is command
R/W=0; we are going to write it
E=1; to set E high
delay: to match the speed [450 ns]
E=0; low to latch the data

• Then we can pass the information 

Load D7-D0 with data
Rs=0; to inform it is word
R/W=0/1; depends on us, whether we would like to read or write
E=1; to set E high-write/low-read
delay: to match the speed [450 ns]
E=0; low to latch the data/high to read

BUSY FLAG:
we are using delay, because the LCD need time to do some internal operation. but we cannot import exact delay, so it may slow down the process. so by using Busy flag we can over come this problem.
here, we use Rs=0 to check the busy flag bit to see if the LCD is ready to receive information. Thus busy flag is D7 and can be read when R/W=1 and Rs=0, as follows: if R/W=1, Rs=0. when D7 =1, the LCD is busy taking case of internal operations and will not accept any new information. when D7=0, the LCD is ready to receive new information.
It is better to use busy flag, rather than imparting delay everywhere use of Busy flag will make the program to run faster.
NOTE: one important thing here is, we need to send low to high signal to enable pin. since we are reading.
PROGRAM:

• sending commands and data to LCDs with a time delay

;calls a time delay before sending next data/command
;p1.0-p1.7 are connected to LCD data pin D0-D7
;p2.0 is connected to Rs pin of LCd
;p2.1 is connected to R/W pin of LCD
;p2.2 is connected to E pin of LCD
    org 0000H
    mov a,#38H    ;init. LCD 2 lines, 5X7 matrix
    acall comwrt    ;call command subroutine
    acall delay    ;give LCD some time
    mov a,#0EH    ;display on,cursor on
    acall comnwrt    ;call command subroutine
    acall delay    ;give LCD some time
    mov a,#01    ;clear LCD
    acall comnwrt    ;call command subroutine
    acall delay     ;give LCD some time
    mov a,#06H    ;shift cursor right
    acall cmnwrt    ;call command subroutine
    acall delay    ;give LCD some time
    mov a,#'h'    ;display letter h
    acall datawrt    ;call display subroutine
    acall delay     ;give LCD sometime
    mov a,#'i'    ;display letter i
    acall datawrt     ;call display subroutine
again:    sjmp again    ;stay here

comnwrt:        ;send command to LCD
           mov p1,a    ;copy reg a to port1
           clr p2.0    ;Rs=0 for command
           clr p2.1    ;R/W=0 for write
          setb p2.2    ;E=1 for high pulse
          acall delay    ;give LCD some time
         clr p2.2    ;give LCD some time
         RET        ;return
   
datawrt:        ;write data to LCD
           mov p1,a    ;copy reg a to port1
           setb p2.0    ;Rs=1 for data
           clr p2.1    ;R/W=0 for write
           setb p2.2    ;E=1 for high pulse
           acall delay    ;give LCD some time
           clr p2.2    ;E=0 for high to low pulse
            ret        ;return

delay:    mov r3,#50    ;50 or higher for fast CPUs
here2:   mov r4,#255    ;r4=255
here:     Djnz r4,here    ;stay until r4 becomes 0
            Djnz r3,here2    ;stay until r3 becomes 0
            return        ;return
             end

• sending commands and data to LCDs using busy flag  

 ;check busy flag before sending data,command to LCD
;p1=data pin, p2.0=Rs,p2.1=R/W,p2.2=E pins
    mov a,#38H    ;init LCD 2 lines,5x7 matrix
    acall command     ;issue command
    mov a,#0EH    ;LCd on, cursor on
    acall command    ;issue command
    mov a,#01H    ;clear LCD command
    acall command    ;issue command
    mov a,#06H    ;shift cursor right
    acall command    ;issue command
    mov a,#86H    ;cursor: line 1,pos 6
    acall command    ;issue command
    mov a,#'h'    ;display letter h
    acall data_dispaly     ;issue data
    mov a,#'i'    ;diaplay letter i
    acall data_display    ;issue data
here:    sjmp here    ;stay here

command:
    acall ready     ;is LCD ready?
    mov p1,a    ;issue command code
    clr p2.0    ;Rs=0 for command
    clr p2.1    ;R/W=0 for write
    setb p2.2    ;E=1 for high pulse
    clr p2.2    ;give LCD some time
    RET        ;return

data_display:
    acall ready    ;is LCD ready?
    mov p1,a    ;copy reg a to port1
    setb p2.0    ;Rs=1 for data
    clr p2.1    ;R/W=0 for write
    setb p2.2    ;E=1 for high pulse
    clr p2.2    ;E=0 for high to low pulse
    ret        ;return  

ready:
    setb p1.7    ;make p1.7 input port
    clr p2.0    ;Rs=0 access command reg
    setb p2.1    ;R/w=1 read command reg
;read command reg and check busy flag
back:    clr p2.2    ;E=0 for low to high pulse
    setb p2.2    ;E=1 low to high pulse
    jb p1.7,back    ;stay until busy flag=0
    ret        ;return
  
    end
i said that we made a very small mistake and we were spending a week in it. the mistake is that,we gave +5V
to VEE pin, we need to vary it as we vary contrast in TV. But, we thought we made mistake in the program and we were checking the program for 5 days
so, always view the problem in various angle, that will give solution quickly...

"The most incomprehensible about the universe is that it is comprehensible"-ALBERT EINSTEIN

Many are filled these questions?

Less than a billionth of a second after the Big Bang....A bubble much small than an atom appeared... That is universe...with in that bubble 4 natural super forces namely Gravity,Electromagnetic,Strong and weak nuclear force existed in it...suddenly the gravity spited and bubble expanded... then the temperature came down enough to create atoms... hydrogen evolved and then it combined to form helium....after nearly 1 billion years later the stars came and heavier atoms like nitrogen, oxygen and carbon were formed...after nearly 9 billion years later matter and gravity combined to form star...this created pressure, which produced heat.. that gave birth to nuclear fusion and the star was created( That the SUN)....The disk of dust around that star are changed into plants and moon... And the temperature of the 3rd plant,earth helped hydrogen di-oxide(water) to built up here...The chemical reaction took place under the water gave rise to living thing... from which we came(many theories explains how we came in this plant)... At last after 13.7 billions years from the Big Bang i'm typing this.......

What are the major evidences which support the Big Bang theory?
    * First of all, we are reasonably certain that the universe had a beginning.
    * Second, galaxies appear to be moving away from us at speeds proportional to their distance. This is called "Hubble's Law," named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929. This observation supports the expansion of the universe and suggests that the universe was once compacted.
    * Third, if the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Radioastronomers Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which pervades the observable universe. This is thought to be the remnant which scientists were looking for. Penzias and Wilson shared in the 1978 Nobel Prize for Physics for their discovery.
    * Finally, the abundance of the "light elements" Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins.  

BIG BANG IN CERN :

CERN ,is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. It is situated in the northwest suburbs of Geneva on the Franco-Swiss border, established in1954.

(LHC)...LHC is about 27 k.m. long and placed 175 m beneath the ground..This collision gave the result more than the scientists of CERN expected... 


GOD?
I feel this discussion is incomplete without speaking about GOD.... Who is he?... is there anything else which exists outside of the natural realm?... is there a Architect behind these thing?...Was God the "First Cause"? What was the super natural thing behind everything that had happen, happening and about to happen?..
 
Being an engineer, I believe in science and not in supernatural... But i won't say there is no GOD.. and pls don't try to prove there is no GOD... Because if someone proves that there is no one called GOD,then suddenly the crime rate will shoot up at lightening speed..many are not involving in crime since they afraid of  GOD...
 so, GOD pls make us to believe that you are watching us and punishing us....