“对称过程"指的是“对称过程".在NFC P2P LLCP中 [英] "Symmetry Procedure" in NFC P2P LLCP
问题描述
我将基于NXP的PN532 NFC芯片实现LLCP/SNEP协议(纯粹出于学习原因)，并且我目前正在研究NFC论坛的LLCP规范.
I'm about to implement the LLCP / SNEP protocol based on a PN532 NFC chip from NXP (purely for learning reasons) and i'm currently studying the LLCP specification of the NFC Forum.
我对ISO 18092中规定的NFC的MAC层非常熟悉，但是在理解LLCP的异步平衡模式(ABM)"的工作方式时遇到了一些问题.
I'm pretty familiar with the MAC-layer of NFC as specified in ISO 18092, but i have some problems understanding how the "asynchronous balanced mode (ABM)" of LLCP works.
据我了解，ABM使发起方和目标方可以随时发送数据(在实际的主/从方法之上).尤其是对于目标公司，我真的不太了解它应该如何工作.
To my understanding, the ABM enables the Initiator and the Target a possibility to send data at any time (on top of the actual master / slave approach). Especially for the Target, i don't really understand how this should work.
例如，我让我的PN532充当启动器，它通过SNEP将NDEF消息推送到支持NFC的智能手机.假设LLCP连接保持启用状态，并且目标方决定在以后的某个时间点将另一个NDEF消息发送回发起方. 当Intiator没有发送请求时，Target如何开始该传输?
For example, i have my PN532 acting as Initiator which pushes a NDEF-message via SNEP to a NFC-enabled Smartphone. Let's say, the LLCP connection stays enabled and the Target decides to send another NDEF-message back to the Initiator at a later point in time. How can the Target start this transmission when the Intiator sends no request for it ?
我不确定，但是这可能与LLCP 1.0的5.8章中指定的对称过程"有关. 我的假设是，如果启动器已收到对先前发送的NDEF消息或信息块/帧的最后确认，则它会在LTO发生之前继续发送"SYMM" -LLC PDU.这使目标有机会发送新的信息块(例如信息框).这一直持续到LLCP链接被停用为止.
I'm not sure, but this is maybe linked to the "Symmetry Procedure" as specificed in chapter 5.8 of LLCP 1.0. My assumption is that in case the Initiator has received the last acknowledge to the previously sent NDEF-message or information block / frame, it continues to send "SYMM"-LLC PDUs just before the LTO occurs. This gives the Target the chance to send a new - for example - information block / frame. This continues until the LLCP link gets deactivated.
有人可以告诉我我的假设是否正确(如果不正确，它实际上是如何工作的..)?
Can anybody please tell me if my assumption is correct (if not, how does it actually work..) ?
PS:对不起，我的英语-这不是我的母语.
PS: Sorry for my english - it isn't my native language.
推荐答案
有人能告诉我我的假设是否正确吗? 它真的有效吗..)?
Can anybody please tell me if my assumption is correct (if not, how does it actually work..) ?
是的，您的假设是正确的.空闲时，启动器将定期将SYMM帧发送到:
Yes, your assumption is correct. When idle, the initiator will regulary send SYMM frames to:
- 检查目标是否仍在响应(又称链接仍在运行)
- 为目标提供发送未决数据帧的机会
这篇关于“对称过程"指的是“对称过程".在NFC P2P LLCP中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
