准备工作

芯片选择

NFC芯片，需要支持ISO14443 Type B协议，比如PN532

阅读ISO 14443

重点阅读如下内容：

7.3.4.1 状态转换图
7.3.5 ~ 7.3.7 REQB相关
7.3.9 REQB的响应ATQB
7.3.10 ATTRIB命令
7.3.11 ATTRIB响应

libnfc

部署

参考官方：http://nfc-tools.org/index.php?title=Libnfc

Tips: 编译时请使用./configure --with-drivers=all --prefix=/usr --sysconfdir=/etc

含义如下：

--with-drivers=all 意思编译所有驱动

--prefix=/usr 安装目录

--sysconfdir=/etc 配置文件目录

使用USB-TTL方式连接

GND    <------>    GND

5V    <------>    VCC

TX    <------>    RX

RX    <------>    TX

配置Debug日志

有两种方式：

在配置文件里设置日志级别

# cat /usr/local/etc/nfc/libnfc.conf

name = “Adafruit PN532 board via UART”

connstring = pn532_uart:/dev/ttyUSB0

allow_intrusive_scan = true

log_level = 3

设置环境变量

两种方式设置环境变量：

<1>程序运行前加给变量赋值，比如

LIBNFC_LOG_LEVEL=3 ./examples/nfc-anticol -g

<2>程序内部利用setenv函数设置环境变量，比如

if (debug)

{

    setenv("LIBNFC_LOG_LEVEL", "3", 1);

}

添加读取UID逻辑

流程简述

根据网上查阅资料，读取步骤如下：

发送REQB
接受REQB的响应ATQB
发送ATTRIB
接受ATTRIB响应
发送读取Type B的UID命令
接受UID

PN532寄存器设置

网上查阅资料，自己试验，需要在libnfc/chips/pn53x.c文件的pn53x_reset_settings函数中加入：

    pn53x_write_register(pnd, PN53X_REG_CIU_Mode, 0xff, 0xff);

    pn53x_write_register(pnd, PN53X_REG_CIU_TxAuto, 0xff, 0x00);

    pn53x_write_register(pnd, PN53X_REG_CIU_TxMode, 0xff, 0x03);

    pn53x_write_register(pnd, PN53X_REG_CIU_RxMode, 0xff, 0x03);

    pn53x_write_register(pnd, PN53X_REG_CIU_TypeB, 0xff, 0x03);

    pn53x_write_register(pnd, PN53X_REG_CIU_Demod, 0xff, 0x4d);

    pn53x_write_register(pnd, PN53X_REG_CIU_GsNOn, 0xff, 0xff);

    pn53x_write_register(pnd, PN53X_REG_CIU_CWGsP, 0xff, 0x3f);

    pn53x_write_register(pnd, PN53X_REG_CIU_ModGsP, 0xff, 0x18);

    pn53x_write_register(pnd, PN53X_REG_CIU_RxThreshold, 0xff, 0x4d);

    pn53x_write_register(pnd, PN53X_REG_CIU_ModWidth, 0xff, 0x68);

    pn53x_write_register(pnd, PN53X_REG_CIU_ManualRCV, 0xff, 0x10);

读取模块

具体利用libnfc实现相关逻辑，核心代码如下：

    uint8_t PUPI[4];

    uint8_t  REQB[5] = { 0x05, 0x00, 0x00 };

    iso14443b_crc_append(REQB, 3);

    transmit_bytes(REQB, 5); //发送REQB

    memcpy(PUPI, abtRx + 1, 4); //复制ATQB的PUIP

    printf("PUPI: ");

    print_hex(PUPI, 4);

    uint8_t Attrib[11] = { 0x1d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x01, 0x01 };

    memcpy(Attrib + 1, PUPI, 4);

    iso14443b_crc_append(Attrib, 9);

    transmit_bytes(Attrib, 11); //发送ATTRIB

    uint8_t ReadGUID[7] = {0x00, 0x36, 0x00, 0x00, 0x08};

    iso14443b_crc_append(ReadGUID, 5);

    transmit_bytes(ReadGUID, 7); //发送读取UID命令

    nfc_close(pnd);

    nfc_exit(context);

    exit(EXIT_SUCCESS);

读取UID

➜  libnfc git:(master) ✗ ./examples/nfc-anticol -g

NFC reader: pn532_uart:/dev/ttyUSB0 opened

Sent bits:     05  00  00  71  ff

Received bits: 50  00  00  00  00  d1  03  00  81  00  70  90  84  10

PUPI: 00  00  00  00

Sent bits:     1d  00  00  00  00  00  08  01  01  32  8d

Received bits: 01  f1  e1

Sent bits:     00  36  00  00  08  57  44

Received bits: 1x  xx  xx  xx  xx  xx  xx  xx  90  00  8a  45

参考资料

论坛：https://www.amobbs.com/thread-5588921-1-1.html?_dsign=1fd689a6
PN532官网手册：https://www.nxp.com/docs/en/user-guide/141520.pdf

巴特西

利用PN532读取二代证UID