基于PN532 NFC近场通讯模块的读卡器

NFC（近场通信）在两个小环形天线之间使用磁感应，常用于各种智能卡的读写。项目采用Arduino Uno开发板读取PN532 NFC模块卡，显示器采用0.96″I2C OLED小屏幕。

使用的物料清单如下：
Arduino Nano开发板
Adafruit PN532 RFID/NFC模块
SSD1306 0.96″OLED显示器
跳线
面包板
Arduino IDE（集成开发环境）

Adafruit PN532 NFC近场通讯模块兼容Arduino设备，运用UART串口进行通讯。可用USB to UART转换器，通过电脑进行测试。用户也可根据自己需要，利用管脚改变数据传输方式，如IIC、SPI等。

该PN532 NFC近场通讯模块基于NXP PN532芯片，包含80C51微控制器内核，集成了13.56MHz下的各种主动/被动式非接触通信方法和协议，支持6种不同的工作模式：
读写器模式，支持ISO/IEC 14443A / MIFARE机制
读写器模式，支持 FeliCa机制
读写器模式，支持ISO/IEC 14443B机制
卡操作模式，支持ISO 14443A / MIFARE机制
卡操作模式，FeliCa机制
ISO/IEC18092，ECM340点对点

首先，我们按照电路图将PN532模块和OLED显示器连接到Arduino开发板：
GND (Ground) <-> GND
VCC (Power supply) <-> 5V
SDA (Data) <-> A4
SCL (Clock) <-> A5

为读卡器更先进，我们采用Adafruit PN532 library，这个数据库兼容Arduino UNO/Nano板，支持I2C or SPI通信模式。下载Adafruit PN532库、Adafruit GFX库和SSD1306 OLED库，将如下代码上传到Arduino Nano开发板：

#include
#include
#include
#include
#include

#define PN532_IRQ (2)
#define PN532_RESET (3) // Not connected by default on the NFC Shield

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define OLED_RESET 4 // Reset pin # (or -1 if sharing Arduino reset pin)
#define SCREEN_ADDRESS 0x3C ///< See datasheet for Address; 0x3D for 128x64, 0x3C for 128x32;

Adafruit_PN532 nfc(PN532_IRQ, PN532_RESET);

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

void setup(void)
{
Serial.begin(115200);
while (!Serial) delay(10); // for Leonardo/Micro/Zero
Serial.println("Hello!");

nfc.begin();

if (!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS))
{
Serial.println(F("SSD1306 allocation failed"));
for (;;); // Don't proceed, loop forever
}

uint32_t versiondata = nfc.getFirmwareVersion();
if (! versiondata)
{
Serial.print("Didn't find PN53x board");
while (1); // halt
}

// Got ok data, print it out!
Serial.print("Found chip PN5");
Serial.println((versiondata>>24) & 0xFF, HEX);
Serial.print("Firmware ver. ");
Serial.print((versiondata>>16) & 0xFF, DEC);
Serial.print('.'); Serial.println((versiondata>>8) & 0xFF, DEC);

display.clearDisplay();
display.setCursor(0, 0); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
display.print("Found chip PN5");
display.print((versiondata >> 24) & 0xFF, HEX);

display.setCursor(0, 20); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
display.print("Firmware ver. ");
display.print((versiondata >> 16) & 0xFF, DEC);
display.print(".");
display.print((versiondata >> 8) & 0xFF, DEC);

nfc.setPassiveActivationRetries(0xFF);

// configure board to read RFID tags
nfc.SAMConfig();

Serial.println("Waiting for an ISO14443A card");

display.setCursor(0, 40); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
display.print("Waiting for NFC Card");
display.display();

}

void loop(void)
{
boolean success;
uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 }; // Buffer to store the returned UID
uint8_t uidLength; // Length of the UID (4 or 7 bytes depending on ISO14443A card type)

success = nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, &uid[0], &uidLength);

if (success) {
Serial.println("Found a card!");
Serial.print("UID Length: ");
Serial.print(uidLength, DEC);
Serial.println(" bytes");
Serial.print("UID Value: ");

display.clearDisplay();
display.setCursor(10, 0); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
display.print("UID Length:");
display.print(uidLength, DEC);
display.print(" bytes");

display.setCursor(35, 20); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
display.println("UID Value: ");
display.setCursor(5, 35); //oled display

for (uint8_t i=0; i < uidLength; i++)
{

Serial.print(" 0x");
Serial.print(uid[i], HEX);
display.print(" 0x");
display.print(uid[i], HEX);
display.display();
}
Serial.println("");
// Wait 1 second before continuing
delay(1000);
}
else
{
// PN532 probably timed out waiting for a card
Serial.println("Timed out waiting for a card");
}
}