Friday 12 October 2012

AUTOMATIC IDENTIFICATION SYSTEMS


Automatic identification systems are a broad class of devices that are used primarily in commercial settings for security authorization and inventory/logistics control. Although different devices may employ radically different technologies, they are united in the common purpose of collecting and tracking data about people or objects. Familiar examples of automatic identification systems are bar codes, magnetic stripes, and shoplifting deterrent tags. The companies and trade groups responsible for developing and implementing such devices are often known collectively as the automatic identification and data capture (AIDC) industry.
Automatic identification systems afford many advantages to businesses. They offer a much faster alternative to manual data entry and verification, and a well-designed system is much more accurate as well. Perhaps the simplest example is at the supermarket checkout counter. If product manufacturers and supermarkets didn't use bar codes, cashiers would have to manually read a code from each item or a list, and key the code into the register. If the cashier misread or mistyped, he would have to try again. This is, of course, what was done before bar code systems were implemented, and it is easy to recognize the efficiencies gained by automating that process.
Beyond efficient data collection, automatic identification systems perform tasks that would be much more difficult to accomplish manually. Magnetic ink character recognition (MICR), for instance, allows merchants to detect whether a customer is attempting to pass a counterfeit check. In addition, many applications of automatic identification are more sophisticated and create greater efficiencies than simple bar coding on consumer products. These include quality control in manufacturing, freight tracking, and biometric and voice recognition for security purposes.

BAR CODES

Bar coding is the most widely used automatic identification technology. Bar codes began to enjoy popularity in the early 1970s with the advent of the Universal Product Code (UPC) for grocery systems. A bar code is a combination of printed bars and spaces representing letters or numbers. According to the Automatic Identification Manufacturers (AIM), an industry trade group, more than 250 different bar code structures exist, but only about a dozen are in widespread use.
A traditional linear bar code such as the UPC includes a start and stop character and a parity or check character. These characters enable the bar code to become a self-contained identification label. While bar codes essentially signal presence or absence of print, they are more properly considered a type of font. A font characterizes or categorizes printed alphabetical or numerical characters based on size and style. Because bar codes contain lines and spaces of varying widths, they resemble font specifications. The smallest width of any bar code is called the X dimension or, alternatively, the module width. Bar codes are also frequently multidirectional: they can be read in either direction, top to bottom or bottom to top, left to right or right to left.
Two-dimensional (2-D) bar codes are a subject of increasing interest to manufacturers and other businesses that require more sophisticated data storage and retrieval than a conventional linear bar code provides. While the newer 2-D codes are commonly labeled as bar codes, they, in fact, don't necessarily use bars at all. Instead, they may employ a matrix of shapes and spaces resembling a pixilated, or highly magnified, black-and-white computer image with a number of geometric shapes scattered throughout. In the technical jargon, these representations are termed "symbologies," and if they appear random to the human eye, they are very meaningful when scanned into an appropriate automatic identification system. Other 2-D codes simply stack multiple linear bar codes on top of one another. The main advantage of 2-D systems is in the large volume of information they can encode in a small space: a single code can store as many as 4,200 alpha-numeric characters, the equivalent of 700 words.

MAGNETIC STRIPES

Magnetic stripes on credit cards, driver's licenses, mass-transit tickets, and numerous other objects function by storing digitally information about the card—and sometimes its user—for retrieval by an electronic reader. The AIM reported in 1998 that more than 20 billion such cards are used each year. Magnetic stripes can be used to reduce data entry, track information, and establish the authenticity of the card in question.
Dating back to the 1960s, magnetic-stripe technology usually involves placing relatively weak magnetic codes on one or more tracks along the magnetic stripe. Although many stripes serve as read-only data sources, generally the stripes can be recoded at any time given the proper equipment. The weakness of the magnetic charge on many consumer cards makes them vulnerable to accidental damage from exposure to magnetic fields. More durable magnetic encoding is available, but because it is more expensive it is usually reserved for more critical applications—those in which the costs of having a bad stripe outweigh the higher material and encoding equipment costs.

SMART CARDS

So-called smart cards may be used in ways similar to magnetic stripe cards, storing personal identification and financial account information, but the underlying technology is quite different and the functions are more diverse. Widely carried in Europe, smart cards contain an embedded microchip with memory for storage, and more advanced ones also have on board a microprocessor that allows the card to make decisions and encrypt data in different ways. This storage and processing power makes smart cards more secure and more versatile than magnetic stripe technology. Among the data that can be stored are images of an individual's face or fingerprint for identification purposes.
Frequently, three zones of information contain the smart card database: secret zone, a private zone, and a public zone. Public zones track transactional information. Private zones contain user identified passwords. Secret zones contain information from the card issuer that can provide access and other restrictions.

RADIO FREQUENCY IDENTIFICATION

An emerging technology, radio frequency identification (RFID) provides tracking information without requiring direct contact with the object being tracked. This is an important feature for applications like shoplifting deterrence, vehicle identification, and animal or person monitoring.
RFID systems utilize a transceiver to send digitally encoded information through an antenna via radio waves. The transceiver may be capable of both reading from and writing to RFID tags, also called transponders, which are placed on the objects being tracked. These tags may contain a battery and be able to actively send signals to the transceiver, or they may be passively controlled by the transceiver. The transceiver is linked to a computer system that interprets and manages the data being sent and received.

BIOMETRICS AND VOICE RECOGNITION

Many security applications use biometrics or voice recognition as a means to positively identify individuals. The most common of these is fingerprinting. While most fingerprints are still processed through the traditional manual ink method, automated fingerprint storage and identification is being used more frequently in law enforcement and other security operations, such as restricting building access and identifying account holders at banks.
Biometrics encompasses a variety of other personal identification methods, all used mostly for security. Retinal and iris scanning techniques involve identifying unique patterns in each human eye. The data describing eye features can be stored using a relatively small amount of memory, and this method may be more definitive than even fingerprinting. Another advantage is that eye scanning systems don't require direct contact with the individual, since the eyes can be scanned by a camera in the distance, and thus don't require any effort or cooperation from the human subject. Another biometric method is hand geometry identification. This method scans the shape of the back and side of a person's hand, and compares the scanned image to its database of stored shapes. This is an older technology that is still used to control access to buildings or other privileges. Individual face and even smell recognition are other biometric tools available.
Finally, voice recognition can be used for personal identification or for general data capturing. Voice-based security systems store a record of speech traits and patterns, which are difficult to counterfeit. A faster-growing use is word recognition for data entry. At its most basic, word recognition is used to identify discrete words, letters, or numbers, such as in an automated telephone menu system that allows users to say the option number of the menu item they wish to choose. More powerful software actually processes continuous speech and turns it into electronic data. This capability is now appearing in many consumer software applications, and has many uses in commercial applications.


source : "
www.referenceforbusiness.com"

Tuesday 2 October 2012

Sensors and Transducers


Simple stand alone electronic circuits can be made to repeatedly flash a light or play a musical note, but in order for an electronic circuit or system to perform any useful task or function it needs to be able to communicate with the "real world" whether this is by reading an input signal from an "ON/OFF" switch or by activating some form of output device to illuminate a single light and to do this we use Transducers.
Transducers can be used to sense a wide range of different energy forms such as movement, electrical signals, radiant energy, thermal or magnetic energy etc, and there are many different types of both analogue and digital input and output devices available to choose from. The type of input or output transducer being used, really depends upon the type of signal or process being "Sensed" or "Controlled" but we can define a transducer as a device that converts one physical quantity into another.
Devices which perform an input function are commonly called Sensors because they "sense" a physical change in some characteristic that changes in response to some excitation, for example heat or force and covert that into an electrical signal. Devices which perform an output function are generally called Actuators and are used to control some external device, for example movement.
Both sensors and actuators are collectively known as Transducers because they are used to convert energy of one kind into energy of another kind, for example, a microphone (input device) converts sound waves into electrical signals for the amplifier to amplify, and a loudspeaker (output device) converts the electrical signals back into sound waves and an example of this type of I/O system is given below.

There are many different types of transducers available in the marketplace, and the choice of which one to use really depends upon the quantity being measured or controlled, with the more common types given in the table below.
Common Transducers
Quantity being
Measured
Input Device
(Sensor)
Output Device
(Actuator)
Light Level
Light Dependant Resistor (LDR)
Photodiode
Photo-transistor
Solar Cell
Lights & Lamps
LED's & Displays
Fibre Optics
Temperature
Thermocouple
Thermistor
Thermostat
Resistive temperature detectors (RTD)
Heater
Fan
Force/Pressure
Strain Gauge
Pressure Switch
Load Cells
Lifts & Jacks
Electromagnet
Vibration
Position
Potentiometer
Encoders
Reflective/Slotted Opto-switch
LVDT
Motor
Solenoid
Panel Meters
Speed
Tacho-generator
Reflective/Slotted Opto-coupler
Doppler Effect Sensors
AC and DC Motors
Stepper Motor
Brake
Sound
Carbon Microphone
Piezo-electric Crystal
Bell
Buzzer
Loudspeaker

Input type transducers or sensors, produce a voltage or signal output response which is proportional to the change in the quantity that they are measuring (the stimulus). The type or amount of the output signal depends upon the type of sensor being used. But generally, all types of sensors can be classed as two kinds, either passive or active.
Active sensors require some form of external power to operate, called an excitation signal which is used by the sensor to produce the output signal. Active sensors are self-generating devices because their own properties change in response to an external effect producing for example, an output voltage of 1 to 10v DC or an output current such as 4 to 20mA DC.
A good example of an active sensor is a strain gauge which is basically a pressure-sensitive resistive bridge network. It does not generate an electrical signal itself, but by passing a current through it (excitation signal), its electrical resistance can be measured by detecting variations in the current and/or voltage across it relating these changes to the amount of strain or force being applied.
Unlike an active sensor, a passive sensor does not need any additional energy source and directly generates an electric signal in response to an external stimulus. For example, a thermocouple or photodiode. Passive sensors are direct sensors which change their physical properties, such as resistance, capacitance or inductance etc. As well as analogue sensors, Digital Sensors produce a discrete output representing a binary number or digit such as a logic level "0" or a logic level "1".


Ngoprek Android


Setelah sekian lama (hampir dua bulan) akhirnya posting blog sendiri lagi.. haha. Kali ini saya akan berbagi sedikit pengalaman bermain android. Yang akan saya bagikan disini adalah cerita pengalaman saya untuk “berani” melakukan oprek android. Karena sebenarnya untuk bahan oprek android, sudah ada dan banyak artikelnya bertebaran di internet dengan video tutorialnya berhamburan di Youtube. Tinggal keberanian dan kemauan belajar dan ngoprek saja yang belum ada. Ini terjadi sama saya, yang beli hp android sekitar beberapa bulan lalu, tetapi baru berani ngoprek belakangan ini haha (nunggu hape nya mbenjol dulu atau garansi habis dulu buihihihi)


Ada beberapa hal dasar yang bisa kita lakukan dalam ngoprek android ini. Mereka adalah: rooting, install aplikasi-aplikasi untuk tweaking/calibrating, sampai akhirnya mencoba flash ROM untuk upgrade firmware, misalnya upgrade dari Froyo (2.2) ke Gingerbread (2.3). Inilah hal-hal yang bisa dipelajari dan dilakukan bagi pemilik android.

Pertama, rooting, adalah kegiatan untuk membuat kita menjadi root/administrator di perangkat android sehingga kita bebas melakukan apa saja. Karena defaultnya beberapa permission dibatasi. Rooting bagi yang suka nge-hack komputer dan tau anatomi hacking, itu sama saja dengan escalation privilege. Tadinya kita user biasa, karena menjalankan sebuah program khusus (exploit) sehingga kita bisa menjadi root/admin di perangkat android deh. Seharusnya proses rooting ini tidak akan berdampak langsung pada hardware android (misalnya: kalo proses eksploitasi sistem android henpun kita-nya gagal). Untuk proses rooting android, udah buanyaaakk caranya bertebaran di internet. Ada yang menggunakan aplikasi tertentu, ada yang jadi paket .apk dan diinstal di komputer, ada yang masuk boot menu dulu, dll. Tapi pada intinya sama, yaitu untuk melakukan eksploitasi dan meng-unlock root pada perangkat.

Kedua, mencoba install aplikasi untuk membuat performance smartphone kita ini semakin aduhai ciamik. Misalnya menginstall aplikasi tweaking processor, memori,  batere, dsb. Ini sudah termasuk kategori ngoprek. Aplikasi semacam ini tersedia kok di market. Tinggal browsing, download, dan install. Biasanya aplikasi seperti ini membutuhkan privilege root, makanya langkah pertama beranikan dulu untuk rooting smartphone kita ini hihih.

Ketiga adalah upgrade firmware kita ke firmware terbaru. Seperti halnya analogi upgrade Windows Vista ke Windows 7 karena (pasti) lebih bagus, stable, dan kenceng Windows 7 daripada Windows Vista dong.. Nah seperti itu pula firmware android kita. Upgrade firmware ada dua macem. Ada upgrade firmware yang official sama yang gak official. Nah yang official tentu saja maksudnya upgrade sesuai dengan rilis vendor hp nya. Misal nih saya pake Samsung, kemudian saya upgrade firmware menggunakan Samsung KIES, berarti saya upgrade menggunakan firmware official dari Samsung. Berbeda halnya jika saya upgrade menggunakan custom ROM yang didapat di internet (misalnya firmware custom dari XDA-Developers). Firmware custom seperti itu ada kelebihan dan kekurangannya. Kelebihannya adalah jika paket-paket yang ditawarkan sama sang pembuat custom firmware tersebut cocok dengan kita, kekurangannya kalau gak cocok. Ya itu aja hahaha. Biasanya custom firmware seperti itu ketika di test lebih oke performance nya daripada firmware yang official. Karena sang pembuat firmware ini suka melakukan tweaking yang ekstrim. Yah tinggal masalah selera aja mau yang adem ayem official atau metal underground nya custom firmware. Untuk oprek yang terakhir ini, memiliki resiko yang besar, yaitu jika terjadi kesalahan atau tidak sesuai prosedur, perangkat android bisa mati permanen alias jadi bangke hahah. Untuk itu, ikuti instruksi upgrade dengan benar. Untuk yang upgrade menggunakan Samsung KIES bisa sedikit lebih tenang karena upgrade firmware-nya menggunakan GUI yang indah dan tinggal klak-klik wizard (resiko salah prosedur hampir tidak ada).

Oh iya, biasanya firmware baru yang ditawarkan dari official vendor selalu lebih telat daripada firmware racikan komunitas. Akhir kata, selamat ngoprek android. Perhatikan apa yang kita lakukan karena ilmu ngopreknya bukan di hasilnya tetapi di setiap langkahnya! Hehe..

Friday 1 April 2011

Compiling *.asm Code to INTEL HEX Format

If the *.asm code list been written then we must convert that in to *.hex then can be downloaded in to flash AT89C51 memory.

For example, the code list is shown below

$mod51

org 00h

jmp mulai

;program dimulai di sini

mulai:

mov r1, #05h

loop:

dec r1

mov a, #01h

mov p1, a

call tunda

kiri:

rl a

mov p1, a

call tunda

cjne a, #80h, kiri

kanan:

rr a

mov p1, a

call tunda

cjne a, #01h, kanan

cjne r1, #00h, loop

ljmp mulai

;

tunda:

mov r4, #02h

ulang:

dec r4

mov r3, #0ffh

tunda1:

dec r3

mov r2, #0ffh

tunda2:

dec r2

cjne r2, #00h, tunda2

cjne r3, #00h, tunda1

cjne r4, #00h, ulang

ret

end

(you must refer to this page for the circuit diagram), when this code been written (for example using notepad), then save it with .asm file extension) by using ASEM.exe (click here to download ) we can to compile and convert it in to *.hex. This process is shown below.


If compiling process completed, and there is no error (we can to assure by open *.lst file extension), so the *.hex can be downloaded in to flash memory of AT89C51


source : http://trensains.com/compile_to_hex.htm

Interruption Handling

Timer/Counters
The AT89C51 has two 16-bit Timer/Counter registers: Timer 0 and Timer 1. The AT89C52 has these two Timer/Counters, and in addition Timer 2. All three can be configured to operate either as Timers or event Counters. As a Timer, the register is incremented every machine cycle. Thus, the register counts machine cycles. Since a machine cycle consists of 12 oscillator periods, the count rate is 1/12 of the oscillator frequency. As a Counter, the register is incremented in response to a 1 to- 0 transition at its corresponding external input pin, T0, T1, or (in the AT89C52) T2. The external input is sampled during S5P2 of every machine cycle. When the samples show a high in one cycle and a low in the next cycle, the
count is incremented. The new count value appears in the register during S3P1 of the cycle following the one in which the transition was detected. Since 2 machine cycles (24 oscillator periods) are required to recognize a l-to-0 transition, the maximum count rate is 1/24 of the oscillator frequency. There are no restrictions on the duty cycle of the external input signal, but it should be held for at least one full machine cycle to ensure that a given level is sampled at least once before it changes. In addition to the Timer or Counter functions, Timer 0 and Timer 1 have four operating modes: (13 bit timer, 16 bit timer, 8 bit auto-reload, split timer). Timer 2 in the AT89C52 has three modes of operation: Capture, Auto-Reload, and baud rate generator.

Timer 0 and Timer 1

Timer/Counters 1 and 0 are present in both the AT89C51 and AT89C52. The Timer or Counter function is selected by control bits C/T in the Special Function Register TMOD (Figure 6). These two Timer/Counters have four operating modes, which are selected by bit pairs (M1, M0) in TMOD. Modes 0, 1, and 2 are the same for both Timer/Counters, but Mode 3 is different. The four modes are described in the following sections.


source : http://trensains.com/interruption.htm