在 iOS 13 上读取 Mifare Ultralight NFC 标签时出现“标签连接丢失”错误

Question

在发现并连接到 Mifare Ultralight 标签（更具体地说，EnOcean PTM 215B）后，我正在尝试使用 NFCMifareTag.sendMifareCommand 方法读取它的页面。问题是我尝试发送的所有命令都会导致“标记连接丢失”错误，这很奇怪，因为我刚刚成功连接到它。

（简化的）代码如下：

// tag has been determined to be of type NFCMifareTag earlier
session.connect(to: tag) { (error: Error?) in
  if (error != nil) {
    return
  }

  print("Connected to the tag")

  let data: [UInt8] = [0x30, 0x04, 0xEE, 0x26] // READ page 4 + CRC
  let dataPacket = Data(bytes: data, count: data.count)

  tag.sendMifareCommand(
    commandPacket: dataPacket,
    completionHandler: { (response: Data?, error: Error?) in
      if nil != error {
        return // <-- "Tag connection lost" error
      }
      // Handle the data as the operation was successful
    }
  )
}

我会很感激任何关于这种行为可能是什么原因的指针和/或想法。如前所述，我尝试了各种不同的数据包，但都完全一样。我还尝试了多种不同的手机来消除硬件问题。该支持刚刚添加到 iOS 13 中，因此我在网上找不到任何可以使用 sendMifareUltralight 命令的示例。

Answer 1

根据 API (CoreNFC/NFCMiFareTag) 将自动计算并插入 CRC。因此，在您的情况下，您只需发送[0x30, 0x04] 即可读取第 4 至第 7 页，读取命令 0x30 将读取 4 页，您将获得 16 个字节。

 /**
 * @method sendMiFareCommand:completionHandler:
 *
 * @param command           The complete MiFare command.  CRC bytes are calculated and inserted automatically to the provided packet data frame.
 * @param completionHandler Completion handler called when the operation is completed.  error is nil if operation succeeds. A @link NFCErrorDomain @link/ error
 *                          is returned when there is a communication issue with the tag. Successfully read data blocks will be returned from the NSData object.
 *
 * @discussion              Send native MIFARE command to a tag.  Support MIFARE UltraLight, Plus, and DESFire products.
 *                          Crypto1 protocol is not supported.  Command chainning is handled internally by the method and the full response composed of the
 *                          individual fragment is returned in the completion handler.
 */
@available(iOS 13.0, *)
func sendMiFareCommand(commandPacket command: Data, completionHandler: @escaping (Data, Error?) -> Void)