NFC approach communication technology
It is evolved from the integration of non-contact radio frequency identification (RFID) and interconnection technology. It combines inductive card readers, inductive cards and point-to-point functions on a single chip, which can identify and exchange data with compatible devices within a short distance . The working frequency is 13.56MHZ, but users who use this mobile payment solution must change to a special mobile phone.
Near field communication is a short-range wireless communication technology developed based on RFID technology. Like RFID, near-field communication information is also transmitted through electromagnetic induction coupling in the radio frequency part of the spectrum. The transmission range of near field communication is smaller than that of RFID, generally around 4cm, which is relatively low cost, high bandwidth, and low energy consumption.
NFC working mode:
- 1. Card mode: It can replace a large number of IC cards including access control cards, bus tickets, tickets, bus cards, etc.
- 2. Point-to-point mode: This mode is similar to infrared, used for data exchange, but the transmission distance is shorter, the transmission creation speed is faster, and the power consumption is low. Linking two NFC-enabled devices can realize point-to-point data transmission, such as downloading music, exchanging pictures, or synchronizing address books.
- 3. Card reader mode: used as a non-contact card reader, such as reading information from tags carrying NFC
The maximum data transmission capacity of NFC is 424Kbit/s, which is much smaller than Bluttooth V2.1 (2.1Mbit/s). Although NFC is inferior to Bluetooth in terms of transmission speed and distance, NFC technology does not require a power source. For mobile phones or mobile consumer electronic products, NFC is more convenient to use. NFC short-distance communication consumes low power, only connects to one machine at a time, and has high confidentiality and security. NFC helps prevent theft of credit cards when interacting with them.
Radio frequency identification technology:
radio frequency identification i.e., RFID (Radio Frequency Identification) technology: is a subset of the NFC technology. RFID is a communication technology that can identify specific targets and read and write corresponding data through wireless signals, without the need to establish mechanical or optical contact between the identification system and specific targets. RFID technologies commonly used in reality include low-frequency (125~134.2kHz), high-frequency (13.56MHz), ultra-high-frequency, microwave and other technologies. RFID readers are divided into mobile and fixed types.
RFID is similar to barcode scanning. For barcode technology, it attaches the encoded barcode to the target, and uses a dedicated scanning reader to use light signals to transmit information from the bar magnet to the scanning reader; and RFID Then use a dedicated RFID reader and a dedicated RFID tag that can be attached to the target, and use frequency signals to transmit information from the RFID tag to the RFID reader.
RFID technology consists of:
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Transponder: It is composed of antenna, coupling element and chip. Generally speaking, tags are used as transponders. Each tag has a unique electronic code and is attached to the object to identify the target object.
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Reader: A device that is composed of an antenna, a coupling element, and a chip to read and write tag information. Can be designed as a handheld reader and a fixed reader
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Application software system: It is the application layer software, which mainly further processes the collected data and uses RFID features for people
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Fast scanning: RFID reader can identify and read several RFID tags at the same time
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Small size and many shapes
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Anti-pollution ability and durability
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Reusable
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Penetrating and barrier-free reading
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Large data memory capacity
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safety
The basic principle of RFID technology:
when the tag enters the magnetic field, it receives the radio frequency signal from the reader, and uses the energy obtained by the induced current to send out the product information stored in the chip (Pressive Tag, passive tag or passive tag), or The tag actively sends a signal of a certain frequency (Active Tag, active tag or active tag). After the reader reads and decodes the information, it is sent to the central information system for relevant data processing.
A complete RFID system consists of the reader and the transponder. And application program composition. Its working principle is that the Reader transmits radio wave energy of a specific frequency to the Transponder to drive the Transponder circuit to send out the internal data. At this time, the Reader receives and interprets the data in turn, and sends them to the application program for corresponding processing. The
RFID card reader and From the perspective of communication and energy sensing methods between electronic tags, RFID can be roughly divided into inductive coupling and backscatter coupling.
The reader can be a reading or reading device according to the structure and technology used, and it is the information control and processing center of the RFID system. The reader usually consists of a coupling module, a transceiver module, a control module and an interface unit. The reader and the transponder generally use half-full duplex communication for information exchange, and the reader provides energy and timing to the passive transponder through coupling. In practical applications, management functions such as the collection, processing and remote transmission of object identification information can be further realized through Ethernet or WLAN. The transponder is the information carrier of the RFID system.
NFC通信总是由一个发起者（Initiator）和接受者（Target）组成。通常Initator主动发送电磁场（RF）可以为被动式接收者（Passive Target）提供电源。由于被动式接受者可以通过发起者提供电源，因此Target可以有非常简单的形式，比如标签、卡、Sticker等。NFC也支持点到点的通信（Peer to Peer），此时参与通信的双方都有电源支持。在Android系统的NFC模块应用中，Android手机通常是作为通信中的发起者，也就是NFC的读写器。Android手机也可以模拟作为NFC通信的接受者。NFC支持以下标准：
- fcANFC-A(ISO 14443-3A)
- NfcBNFC-B(ISO 14443-3B)
- NfcFNFC-F(JIS 6319-4)
- NfcVNFC-V(ISO 15693)
- IsoDepISO-DEP(ISO 14443-4)
- MifareClassic
- MifareUltralight
When the Android phone starts the NFC program and detects a TAG, the TAG distribution system will automatically create an intent that encapsulates the NFC TAG information. If more than one application can handle this Intent, then the phone will pop up a dialog box for the user to select the Activity that handles the Tag. There are 3 types of
intents defined in the TAG distribution system, arranged in order of priority: -NDEF_DISCOVERED
-TECH_DISCOVERED
-TAG_DISCOVERED