With the continuous development of radio frequency technology, the field of wireless communication has been paid more and more attention, and as a non-contact IC card in the field of wireless communication, it has been everywhere. Such as: the bus card of the bus, the meal card in the canteen, the fitness card in the club, etc., almost involved in all areas of our lives. In general, the small-scale, mature non-contact IC card system uses a single-chip microcomputer as the core processor, and the transmission network is RS485/422 or CAN bus. Such a system structure has the advantages of powerful control function, low price, and easy development and design. Therefore, it has become the first choice for various small-scale contactless IC card systems. However, due to the operation speed, memory space and limitation of the instruction system of the MCU, in the network system of large-scale non-contact IC card, if a single-chip microcomputer is used as the core processor, the waiting time and the amount of data storage are bound to be Exceeded the range of system indicators. The traditional solution is to increase the number of microcontrollers and classify the IC card information into the corresponding microcontroller. Although this can solve the above problems, it also brings disadvantages. On the one hand, this will increase the cost of the whole system, on the other hand, it will increase the complexity and uncertainty of the system, which brings a lot of inconvenience to the user.
In view of the above situation, this paper proposes a design idea of ​​a non-contact IC card control system based on a fast DSP chip. This system uses DSP chip instead of multiple MCUs as the core processor, and utilizes the advantages of DSP processing speed to optimize the overall performance of the system. At the same time, the price of a DSP is lower than the sum of multiple MCUs, so the cost of the system is also Taking advantage of this, on the basis of this, the DSP chip processor can also store a large amount of IC card authority data.
1 system architecture
The overall design of the system is shown in Figure 1. The system constitutes a typical control network. When the reader MF RC2500 is within the magnetic field of the detection terminal, it will receive the RF pulse of the external signal while receiving the RF. The signal is demodulated in the pulse and sent to the controller TMS320F2407. The controller TMS320F2407 reads and writes the card reader MFRC500, and after receiving the information for analysis and processing, it adopts RS-485/422 in half (full) duplex communication mode. Signals are sent to the server to form a control network for the bus topology. During the system working process, the server monitors the status of the controller at any time, determines the working condition of the controller, and detects the status of the card reader. The server and controller work in master-slave mode, and the control commands issued by the server and the response information returned by the controller are transmitted through the eight-core cable.
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Philips' MF RC500 reader is part of a highly integrated reader IC family for 13.56 MHz contactless communication. This series of readers utilizes advanced modulation and demodulation concepts and fully integrates all types of passive contactless communication methods and protocols at 13.56 MHz. It is the core module for wireless communication in this system. The MFRC500 series modules support the 1 to 4 parts of the SO14443TypeA protocol and the Mifare classic protocol. The internal transmitter part can directly drive the near-operating distance antenna without adding active circuits. It uses the CRYPO1 encryption algorithm and contains a secure non-volatile internal key. Memory. The chip integrates an analog modulation and demodulation circuit, which can work with a minimum of peripheral circuits, and supports I2C interface, UART interface, and SPI interface. It is especially suitable for the application of the ISO14443 standard for water, electricity, gas meters, vending machines, access control, elevators, water dispensers, telephones and other billing systems or card readers for identification systems.
2 hardware structure
The parallel interface of the MF RC500 can be connected to a variety of microprocessors with different types of parallel interfaces. After each power-on reset, the MF RC500 will reset its parallel interface mode and determine the current logic level through the corresponding pin. The type of interface of the microprocessor to synchronize with the microprocessor. The system adopts the construction method of read-write strobe separation and address/data bus multiplexing. The connection schematic diagram is shown in Figure 2. It can be seen from Fig. 2 that the system adopts the interrupt working mode, that is, the TMS320F2407 controls it according to the interrupt information provided by the MF RC500. In addition, according to the actual situation, the system can also use the query mode to operate the non-contact IC chip.
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MF RC500 address bus A2, A1 and A0 are always 011; reset pin negative transition from TMS320F2407 will reset MF RC500, TSS320F2407 DS pin generates chip select signal NCS and pin output read control signal NRD and write control signal NWR, The A4 pin generates the address latch signal ALE (the address line and the data line of the TMS320F2407 are independent, there is no operation of the ALE address, in order to be able to access the MF RC500, here by programming the output of the I/O pin), TMS320F2407 The interrupt pin INT0 is directly connected to the interrupt pin of the MFRC500. The interrupt output of the MF RC500 will trigger the TMS320F2407 to enter the corresponding interrupt service routine.
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