我是Arduino的新手。我在看Makecourse tutorial on RC522 RFID reader/writer
我粘贴了下面的脚本。基本上，它检测到卡然后将一些数据写入块2.
在编译和上传代码之后，我将一张卡片放到RFID阅读器上，它可以工作 - 但只需一次。当我张贴第二张卡时，没有任何反应。为什么呢？
我已将此脚本与mfrc522库中的其他示例脚本进行比较，它们非常相似 - 在void loop（）部分中，它检查NewCardPresent ... ReadCardSerial ...然后继续运行预期的操作。我已经尝试过这些示例脚本，我可以继续向读者提供一张新卡，然后脚本会重新运行。
然而，这个草图，循环只运行一次。是结构吗？如何编辑它以使其连续运行？如果答案很简单，我道歉：/
#include <SPI.h>//include the SPI bus library
#include <MFRC522.h>//include the RFID reader library
#define SS_PIN 10 //slave select pin
#define RST_PIN 5 //reset pin
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
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 - all six key bytes are set to 0xFF at chip delivery from the factory.
// Since the cards in the kit are new and the keys were never defined, they are 0xFF
// if we had a card that was programmed by someone else, we would need to know the key to be able to access it. This key would then need to be stored in 'key' instead.
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
}
}
int block=2;//this is the block number we will write into and then read. Do not write into 'sector trailer' block, since this can make the block unusable.
byte blockcontent[16] = {"makecourse_____"};//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.
byte readbackblock[18];//This array is used for reading out a block. The MIFARE_Read method requires a buffer that is at least 18 bytes to hold the 16 bytes of a block.
void loop()
{
/*****************************************establishing contact with a tag/card**********************************************************************/
// Look for new cards (in case you wonder what PICC means: proximity integrated circuit card)
if ( ! mfrc522.PICC_IsNewCardPresent()) {//if PICC_IsNewCardPresent returns 1, a new card has been found and we continue
return;//if it did not find a new card is returns a '0' and we return to the start of the loop
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial()) {//if PICC_ReadCardSerial returns 1, the "uid" struct (see MFRC522.h lines 238-45)) contains the ID of the read card.
return;//if it returns a '0' something went wrong and we return to the start of the loop
}
// Among other things, the PICC_ReadCardSerial() method reads the UID and the SAK (Select acknowledge) into the mfrc522.uid struct, which is also instantiated
// during this process.
// The UID is needed during the authentication process
//The Uid struct:
//typedef struct {
//byte size; // Number of bytes in the UID. 4, 7 or 10.
//byte uidByte[10]; //the user ID in 10 bytes.
//byte sak; // The SAK (Select acknowledge) byte returned from the PICC after successful selection.
//} Uid;
Serial.println("card selected");
/*****************************************writing and reading a block on the card**********************************************************************/
writeBlock(block, blockcontent);//the blockcontent array is written into the card block
//mfrc522.PICC_DumpToSerial(&(mfrc522.uid));
//The 'PICC_DumpToSerial' method 'dumps' the entire MIFARE data block into the serial monitor. Very useful while programming a sketch with the RFID reader...
//Notes:
//(1) MIFARE cards conceal key A in all trailer blocks, and shows 0x00 instead of 0xFF. This is a secutiry feature. Key B appears to be public by default.
//(2) The card needs to be on the reader for the entire duration of the dump. If it is removed prematurely, the dump interrupts and an error message will appear.
//(3) The dump takes longer than the time alloted for interaction per pairing between reader and card, i.e. the readBlock function below will produce a timeout if
// the dump is used.
//mfrc522.PICC_DumpToSerial(&(mfrc522.uid));//uncomment this if you want to see the entire 1k memory with the block written into it.
readBlock(block, readbackblock);//read the block back
Serial.print("read block: ");
for (int j=0 ; j<16 ; j++)//print the block contents
{
Serial.write (readbackblock[j]);//Serial.write() transmits the ASCII numbers as human readable characters to serial monitor
}
Serial.println("");
}
这是草图附带的功能：
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;}//block number is a trailer block (modulo 4); quit and send error code 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));
//byte PCD_Authenticate(byte command, byte blockAddr, MIFARE_Key *key, Uid *uid);
//this method is used to authenticate a certain block for writing or reading
//command: See enumerations above -> PICC_CMD_MF_AUTH_KEY_A = 0x60 (=1100000), // this command performs authentication with Key A
//blockAddr is the number of the block from 0 to 15.
//MIFARE_Key *key is a pointer to the MIFARE_Key struct defined above, this struct needs to be defined for each block. New cards have all A/B= FF FF FF FF FF FF
//Uid *uid is a pointer to the UID struct that contains the user ID of the card.
if (status != MFRC522::STATUS_OK) {
Serial.print("PCD_Authenticate() failed: ");
Serial.println(mfrc522.GetStatusCodeName(status));
return 3;//return "3" as error message
}
//it appears the authentication needs to be made before every block read/write within a specific sector.
//If a different sector is being authenticated access to the previous one is lost.
/*****************************************writing the block***********************************************************/
status = mfrc522.MIFARE_Write(blockNumber, arrayAddress, 16);//valueBlockA is the block number, MIFARE_Write(block number (0-15), byte array containing 16 values, number of bytes in block (=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");
}
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));
//byte PCD_Authenticate(byte command, byte blockAddr, MIFARE_Key *key, Uid *uid);
//this method is used to authenticate a certain block for writing or reading
//command: See enumerations above -> PICC_CMD_MF_AUTH_KEY_A = 0x60 (=1100000), // this command performs authentication with Key A
//blockAddr is the number of the block from 0 to 15.
//MIFARE_Key *key is a pointer to the MIFARE_Key struct defined above, this struct needs to be defined for each block. New cards have all A/B= FF FF FF FF FF FF
//Uid *uid is a pointer to the UID struct that contains the user ID of the card.
if (status != MFRC522::STATUS_OK) {
Serial.print("PCD_Authenticate() failed (read): ");
Serial.println(mfrc522.GetStatusCodeName(status));
return 3;//return "3" as error message
}
//it appears the authentication needs to be made before every block read/write within a specific sector.
//If a different sector is being authenticated access to the previous one is lost.
/*****************************************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");
}
答案 0 :(得分：1)
Arduino Loop（）应该被无限调用，而不像你观察到的那样。 因此，您需要检查以下两种可能性。 1）在循环开始时发生任何返回（）。我看到了两个回复陈述。您最好在它们之间插入调试消息，以便在返回此函数之前知道到达了多远。 2）任何阻塞都在循环（）中徘徊。我不知道，但你最好也检查一下。
答案 1 :(得分：1)
结果在脚本末尾添加了这几行解决了问题：
delay(1000);
mfrc522.PICC_HaltA();
mfrc522.PCD_StopCrypto1();
：）
答案 2 :(得分：0)
我认为问题不在于循环。它在不断毁灭。您可以通过在循环开始时使用一些串行打印来检查它。问题是第一次检测到卡后，该程序第二次没有识别卡，因此请专注于此。循环很好。