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