RFID reader circuit design scheme of Cortex-M0

SLRC610 ($2.4466) is a member of NXP’s new generation of multi-protocol wireless near-field chips, it is a highly integrated transceiver chip for 13.56MHz contactless communication, supports and complies with ISO/IEC15693, EPCUID and ISO /IEC18000-3 mode 3/EPC Class-1 HF protocol card. There are three types of communication interfaces between it and the host: SPI, UART, and I2C bus (including I2C and I2CL modes). Plus, it’s more secure than the previous generation, supporting Secure Access Module (SAM) connections.

RF chip SLRC610 ($2.4466)

SLRC610 ($2.4466) is a member of NXP’s new generation of multi-protocol wireless near-field chips, it is a highly integrated transceiver chip for 13.56MHz contactless communication, supports and complies with ISO/IEC15693, EPCUID and ISO /IEC18000-3 mode 3/EPC Class-1 HF protocol card. There are three types of communication interfaces between it and the host: SPI, UART, and I2C bus (including I2C and I2CL modes). Plus, it’s more secure than the previous generation, supporting Secure Access Module (SAM) connections.

RFID reader circuit design scheme of Cortex-M0

Module hardware design

The module is mainly composed of communication upgrade interface, debugging interface, prompt signal, LPC812 ($0.6375), SLRC610 ($2.4466), and built-in antenna of the module. The block diagram of the module is shown in Figure 1.

Main control chip circuit design

LPC812 ($0.6375) is the most configured model of LPC800 series. It has three packages: TSSOP16, SO2O and TSSOP20 ($9.9900). Because it is designed for small modules, sO2O plastic small package is selected. Since LPC812 ($0.6375) supports assigning a special function to an I/O pin through the switch matrix, it is possible to fully consider which pin to assign a certain function to when designing the schematic diagram, which is convenient for wiring and has good performance. . In addition, in this design, the built-in 1% precision 12 MHz internal RC oscillator of LPC812 ($0.6375) is used as the system clock. The main control chip circuit is shown in Figure 2.

RFID reader circuit design scheme of Cortex-M0

RF chip circuit design

SLRC610 ($2.4466) only has a small HVQFN32 package. Pay special attention to its 33rd pin, which is a square surface facing the middle of the PCB surface. This surface must be well grounded, otherwise there will be some strange phenomena. SLRC610 ($2.4466) supports four interfaces: SPI, I2C bus, I2CI and UART. It will judge the current host interface type through the combination of IFSEL0 and IFSEL1 levels after power-off reset. This design uses a hard-coded SPI interface, which requires IFSEL0 to be grounded and IFSEL1 to be connected to VCC in the hardware circuit. The RF chip circuit is shown in Figure 3. The towel, the 33-pin VSS in the SLRC610 ($2.4466) chip is used for grounding and heat dissipation, so this pin must be well grounded.

RFID reader circuit design scheme of Cortex-M0

The matching circuit of the antenna includes an EMC low-pass filter (L1, L2, C5, C6), a matching circuit (C3, C4, C7~C1O), a receiving circuit (R2, R3, C15) and the antenna itself. The component values ​​of the receiving circuit need to be specially designed and adjusted according to the actual situation of the board. The size of this design module is limited, the receiving circuit adopts a single-ended mode with fewer components, and the antenna coil is built in the middle layer of the PCB to facilitate application and reduce the volume.

The newer main control and RF chips are used in the design of this module, with low price and strong performance, and there will be no problems in supply and price for a long time. The LPC800 series not only adds practical functions such as switch matrix to facilitate user circuit design, but also integrates the ISP upgrade function of the older generation of microcontrollers. This article describes in detail the use of these two chips and the debugging methods and steps of the modules. The module adopts the components of the veneer package, which has the characteristics of low cost, low power consumption, small size, and long distance between reading and writing cards. It is very convenient to use and has high application value.

The Links:   G190SF01-V0 FP75R12KT3

Author: Yoyokuo