NFC is closely wireless communication, which is initiated by NXP, a wireless technology that is mainly pushed by Nova, Sony, etc. - combined with inductive card readers, inductive cards, and point-to-point functions on a single chip. Recognition and data exchange with compatible devices within a short distance.
1 background
The NFC has the characteristics of bidirectional connection and identification, operating in a 13.56 MHz frequency range, and the distance is close to 10 cm. NFC technology promotes standardization under the framework of ISO18092, ECMA 340 and ETSITS 102 190, and is also compatible with extensive ISO 14443 Type-a, B, and Felica standard non-contact smart cards.
The latest NFC specification developed by the European Telecommunications Standards Association (ETSI) can provide a fully compatible platform for mobile phone manufacturers and telecom operators to launch next-generation NFC devices and services: PN544 is fully compatible with all released all lines Agreement (SWP) Connect the NFC specification for the SIM card and host controller interface (HCI).
PN65o is PN544 plus NXP SMARTMX security modules, PN544 and PN65o hardware PIN is fully compatible with PIN. At the same time, the PN65o / PN544 also provides a variety of host interface selection to ensure a relaxed integration of HIGH SPEED UART, SPI, I2C, and supports a variety of RF interface protocols: ISO14443A / B, ISO15693, Mifare, Felica. In addition, NXP Work closely with Gemalto, Oberthur Technologies and Giesecke & Devrient, etc. to ensure interoperability of SWP interfaces including Mifare technology.
2 NFC electronic wallet overall structure
2.1 Structure of NFC PN544 / PN65O
A structural block diagram of NFC PN544 / PN65O as shown below.
Figure 1 NFC PN544 / PN65O hardware circuit block diagram
2.2 PN544 and PN65O dominant characteristics
(1) Small size, easy to perform dimension optimization
(2) Low power consumption
(3) Battery shutdown and low power mode
(4) Optional software stack with platform-independent
(5) Provide GPIO Port for external unit control
(6) Interrupt IRQ can make the command communication of the external control unit easier
(7) Support Secure Unit Control Interface
(8) Integrated power control unit
3 About NXP latest NFC e-wallet solution
The NFC electronic wallet function is to implement mobile payment and data exchange functions from the PN544 NFC controller (PN65o built-in security module) and security modules.
3.1 RF section
The NFC RF circuit consists of an EMC filter circuit, a matching circuit, a receiving circuit, an antenna, and the like.
3.2 EMC circuit
Since the system is based on the operating frequency of 13.56 MHz. This frequency is produced by quartz crystals. At the same time, high-order harmonics will also occur. In order to meet the internal electromagnetic compatibility rules, the high-order harmonics of 13.56 MHz, five and five times or more must be appropriately suppressed. Therefore, the EMC circuit is configured as an LC low pass filter, which is used to filter out high-end harmonics.
3.3 Antenna Matching Circuit
Since the antenna coil itself is a low impedance device, in order to be able to deliver the energy sent by the NFC IC to the antenna, a matching circuit must be added between the antenna and the NFC IC. Eliminating the energy loss formed by the signal reflection caused by mismatches.
3.4 Receiving Circuit
Composed of R127, C118, R128, C119, the VMID potential generated inside the chip acts as the input potential of the RX pin, which is required to ground the VMID using the capacitor. The bias voltage of the VMID can increase the voltage driver of the RX pin. Figure 2 shows the NFC radio frequency receiving circuit.
Figure 2 NFC radio frequency part circuit
3.5 NFC and SIM Card Security Module Interface Circuit
The NFC IC has a SWP line-in interface that implements data communication with the SIM card, and its reference circuit is shown in Figure 3 below.
Figure 3 NFC and SIM card security module interface circuit
4 PN65o / PN544 Demo Board display
About PN65O / PN544 Demo Board Shows As shown in Figure 4, such as a schematic diagram of the Android development platform.
Figure 4: PN65O / PN544 Demo Board Schematic
Figure 5: Android development platform display
5 conclusion
This article is based on the operating frequency of 13.56MHz, with the mobile phone as the trading platform. The mobile payment and data is implemented by the NXP PN544 NFC controller (PN65o built-in security module) and security module. Exchange function provides convenient, safe, extraordinary experience for electronic payment.
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Source: Wiku Electronic Market Network
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