我在使用MFRC522 RFID的Arduino IDE上一直遇到编译错误，说它需要数据类型

Question

我一直在使用Arduino的标准代码来使RFID正常工作

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

#define SS_PIN 10
#define RST_PIN 9
MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance.

void setup() 
{
  Serial.begin(9600);   // Initiate a serial communication
  SPI.begin();      // Initiate  SPI bus
  mfrc522.PCD_Init();   // Initiate MFRC522
  Serial.println("Approximate your card to the reader...");
  Serial.println();

}
void loop() 
{
  // Look for new cards
  if ( ! mfrc522.PICC_IsNewCardPresent()) 
  {
    return;
  }
  // Select one of the cards
  if ( ! mfrc522.PICC_ReadCardSerial()) 
  {
    return;
  }
  //Show UID on serial monitor
  Serial.print("UID tag :");
  String content= "";
  byte letter;
  for (byte i = 0; i < mfrc522.uid.size; i++) 
  {
     Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
     Serial.print(mfrc522.uid.uidByte[i], HEX);
     content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
     content.concat(String(mfrc522.uid.uidByte[i], HEX));
  }
  Serial.println();
  Serial.print("Message : ");
  content.toUpperCase();
  if (content.substring(1) == "BD 31 15 2B") //change here the UID of the card/cards that you want to give access
  {
    Serial.println("Authorized access");
    Serial.println();
    delay(3000);
  }

 else   {
    Serial.println(" Access denied");
    delay(3000);
  }
}  

我不断收到这些错误

RFID:6: error: 'MFRC522' does not name a type
RFID.ino: In function 'void setup()':
RFID:12: error: 'mfrc522' was not declared in this scope
RFID.ino: In function 'void loop()':
RFID:20: error: 'mfrc522' was not declared in this scope
RFID:25: error: 'mfrc522' was not declared in this scope
RFID:33: error: 'mfrc522' was not declared in this scope

为什么会这样？我正在使用Arduino 1.0.5，因为我的Uno驱动程序不会加载较新的版本。如果已经有关于此的帖子，我找不到它，那么也将附上该链接