Android MIFARE NFCA源码解析

Android MIFARE NFCA源码解析
TagTechnology定义了所有标签的共有接口类
BasicTagTechnology 实现了TagTechnology的一些接口

再有具体的标签协议继承BasicTagTechnology
NFC-A 遵循ISO 14443-3A协议。

关键字
ATQA Answer To Request acc. to ISO/IEC 14443-4
ATS Answer To Select acc. to ISO/IEC 14443-4
DIF Dual Interface (cards)
COS Card Operating System
CL Cascade Level acc. to ISO/IEC 14443-3
CT Cascade Tag, Type A
n.a. not applicable
NFC Near Field Communication
PCD Proximity Coupling Device (“Contactless Reader”)
PICC Proximity Integrated Circuit (“Contactless Card”)
PKE Public Key Encryption (like RSA or ECC)
REQA Request Command, Type A
SAK Select Acknowledge, Type A
Select Select Command, Type A
RID Random ID, typically dynamically generated at Power-on Reset
RFU Reserved for future use
UID Unique Identifier, Type A
NUID Non-Unique Identifier

当读卡器检测到了卡片就会发送REQA请求命令,在感应区内的卡片接收到REQA,将会反馈ATQA消息。
SAK的第六位表明PICC卡是否符合ISO/IEC14443-4 标准。

Android MIFARE NFCA源码解析

Android MIFARE NFCA源码解析

The bit numbering in the ISO/IEC 14443 starts with LSBit = bit 1, but not LSBit =bit 0. So one byte counts bit 1...8 instead of bit 0...7.
The ISO/IEC 14443 transfers LSByte first. So e.g. 0x 00 44 (ATQA of the MFUL) is often received as 0x 44 00.

ATQA ISO/IEC 14443-3 协议标准

Android MIFARE NFCA源码解析

ATQA Coding of NXP Contactless Card ICs

Android MIFARE NFCA源码解析

Android MIFARE NFCA源码解析

SAK coding of NXP Contactless Card ICs

Android MIFARE NFCA源码解析

Android MIFARE NFCA源码解析

Android MIFARE NFCA源码解析

如下图可以根据ATQA,SAK,ATS判断厂家和产品的类型

举例
<string name="tag_000409">MIFARE Mini, NXP</string>
<string name="tag_000408">MIFARE Classic 1k, NXP</string>
<string name="tag_000218">MIFARE Classic 4k, NXP</string>
<string name="tag_004218">MIFARE Classic 4k, NXP</string>
<string name="tag_004400">MIFARE Ultralight, NXP</string>
<string name="tag_000488">MIFARE Classic 1K, Infineon</string>
getResources().getIdentifier(prefix + atqa + sak + ats, "string", getPackageName())

Android MIFARE NFCA源码解析

NfcA get(Tag tag)
获取NFCA一个实例,首先判断
tag.hasTech(TagTechnology.NFC_A)
这个TAG是否是NFC_A TAG。
然后才生成NFC A TAG实例
getAtqa()
读写器呼叫磁场内的卡片,卡片对呼叫做出应答。收到卡呼叫命令后,卡片将对命令做出应答(Answer To Request,ATQA),
告诉读写器自己是否遵守面向比特的防冲突机制,
ATQA/SENS_RES
这里获取卡片应答的消息。

举例:用来判断是否是Mifare Classic tag
NfcA nfca = NfcA.get(tag);
byte[] atqa = nfca.getAtqa();
if (atqa[1] == 0 &&(atqa[0] == 4 || atqa[0] == (byte)0x44 ||atqa[0] == 2 || atqa[0] == (byte)0x42))

getSak()
SAK/SEL_RES
返回选择命令的信息
举例:
byte sak = (byte)nfca.getSak();
if (sak == 8 || sak == 9 || sak == (byte)0x18 ||sak == (byte)0x88)

Transceive()
Send raw NFC-A commands to the tag and receive the response.
发送命令到TAG,并接收返回值。
注意:
1:发送命令时不用增加CRC,因为系统会自动加。
2:发送命令是完整的字节。SENS_REQ3:因为是I/O操作,会发生阻塞,不用在主线程调用这个函数。

getMaxTransceiveLength()
获取最大的发送字节长度

  
  
参考文档
NfcA.java
http://www.nxp.com/documents/application_note/AN10833.pdf
http://nfc-tools.org/index.php?title=ISO14443A
  
时间
起草与2015-10-15
  

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