108个传感器之-射频识别模块RC522（47）

介绍

借助基于RFID的步行自动结帐解决方案，可以用来实现快速购物车结账。不需要再等待某人一一敲响购物车中的每个物品；现在，利用附加在项目上的RFID标签，将几乎立即检测到购物车中的每个项目。

对于大多数基于RFID的Arduino项目，RC522 RFID读取器/写入模块是一个不错的选择。它是低功率，低成本，非常坚固，易于接入，并且在业余爱好者中非常受欢迎。

工作原理

RFID或射频标识系统由两个主要组件组成，标签添加到要识别的客户端和读取标签的服务端。

读取器由射频模块和产生高频电磁场的天线组成。而标签通常是一个被动设备（没有电池）。它由一个存储和处理信息的微芯片以及用于接收和传输信号的天线。

引脚连接

RC522		Arduino
VCC		3.3V
GND		GND
RST		A0
MISO / SCL / Tx		A5
MOSI		A6
SCK		A9
SS / SDA / Rx		A7

Tips: 用例使用的是 esp32-c3-supermini，对应的引脚是 A4、A5，如果在 platformIO 上开发的话，直接输入引脚名称会提示当前的引脚对应数字号。

代码示例

写入端

这个是给卡片写入数据的案例。

#include <Arduino.h>
#include <SPI.h>
#include <MFRC522.h>

#define SS_PIN A7
#define RST_PIN A0

MFRC522 mfrc522(SS_PIN, RST_PIN); // instatiate a MFRC522 reader object.
MFRC522::MIFARE_Key key;					// create a MIFARE_Key struct named 'key', which will hold the card information

// this is the block number we will write into and then read.
int block = 2;

byte blockcontent[16] = {"Last-Minute-Engg"}; // an array with 16 bytes to be written into one of the 64 card blocks is defined
// byte blockcontent[16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};  //all zeros. This can be used to delete a block.

// This array is used for reading out a block.
byte readbackblock[18];

void setup()
{
	Serial.begin(9600); // Initialize serial communications with the PC
	SPI.begin();				// Init SPI bus
	mfrc522.PCD_Init(); // Init MFRC522 card (in case you wonder what PCD means: proximity coupling device)
	Serial.println("Scan a MIFARE Classic card");

	// Prepare the security key for the read and write functions.
	for (byte i = 0; i < 6; i++)
	{
		key.keyByte[i] = 0xFF; // keyByte is defined in the "MIFARE_Key" 'struct' definition in the .h file of the library
	}
}

void loop()
{
	// Look for new cards
	if (!mfrc522.PICC_IsNewCardPresent())
	{
		return;
	}

	// Select one of the cards
	if (!mfrc522.PICC_ReadCardSerial())
	{
		return;
	}
	Serial.println("card selected");

	// the blockcontent array is written into the card block
	writeBlock(block, blockcontent);

	// read the block back
	readBlock(block, readbackblock);
	// uncomment below line if you want to see the entire 1k memory with the block written into it.
	// mfrc522.PICC_DumpToSerial(&(mfrc522.uid));

	// print the block contents
	Serial.print("read block: ");
	for (int j = 0; j < 16; j++)
	{
		Serial.write(readbackblock[j]);
	}
	Serial.println("");
}

// Write specific block
int writeBlock(int blockNumber, byte arrayAddress[])
{
	// this makes sure that we only write into data blocks. Every 4th block is a trailer block for the access/security info.
	int largestModulo4Number = blockNumber / 4 * 4;
	int trailerBlock = largestModulo4Number + 3; // determine trailer block for the sector
	if (blockNumber > 2 && (blockNumber + 1) % 4 == 0)
	{
		Serial.print(blockNumber);
		Serial.println(" is a trailer block:");
		return 2;
	}
	Serial.print(blockNumber);
	Serial.println(" is a data block:");

	// authentication of the desired block for access
	byte status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, trailerBlock, &key, &(mfrc522.uid));
	if (status != MFRC522::STATUS_OK)
	{
		Serial.print("PCD_Authenticate() failed: ");
		Serial.println(mfrc522.GetStatusCodeName(status));
		return 3; // return "3" as error message
	}

	// writing the block
	status = mfrc522.MIFARE_Write(blockNumber, arrayAddress, 16);
	// status = mfrc522.MIFARE_Write(9, value1Block, 16);
	if (status != MFRC522::STATUS_OK)
	{
		Serial.print("MIFARE_Write() failed: ");
		Serial.println(mfrc522.GetStatusCodeName(status));
		return 4; // return "4" as error message
	}
	Serial.println("block was written");
}

// Read specific block
int readBlock(int blockNumber, byte arrayAddress[])
{
	int largestModulo4Number = blockNumber / 4 * 4;
	int trailerBlock = largestModulo4Number + 3; // determine trailer block for the sector

	// authentication of the desired block for access
	byte status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, trailerBlock, &key, &(mfrc522.uid));

	if (status != MFRC522::STATUS_OK)
	{
		Serial.print("PCD_Authenticate() failed (read): ");
		Serial.println(mfrc522.GetStatusCodeName(status));
		return 3; // return "3" as error message
	}

	// reading a block
	byte buffersize = 18;																									// we need to define a variable with the read buffer size, since the MIFARE_Read method below needs a pointer to the variable that contains the size...
	status = mfrc522.MIFARE_Read(blockNumber, arrayAddress, &buffersize); //&buffersize is a pointer to the buffersize variable; MIFARE_Read requires a pointer instead of just a number
	if (status != MFRC522::STATUS_OK)
	{
		Serial.print("MIFARE_read() failed: ");
		Serial.println(mfrc522.GetStatusCodeName(status));
		return 4; // return "4" as error message
	}
	Serial.println("block was read");
}

读取端

小结

待完善…

参考

dev 的艺术空间

RC522