使用 iPhone 6/iOS 8 读取 NFC 标签 [英] Reading NFC Tags with iPhone 6 / iOS 8
问题描述
既然苹果刚刚宣布 iPhone 6 将配备 NFC 芯片，有谁知道 iOS 8 是否会为 iPhone 6 设备启用读取/检测 RFID 标签?任何人有任何细节可以分享吗?
iPhone6/6s/6+ 并非设计用于读取被动 NFC 标签(又名发现模式).关于这个主题有很多错误信息，所以我想提供一些有形的信息供开发人员考虑.缺少NFC标签读取支持不是因为软件，而是因为硬件.要了解原因，您需要了解 NFC 的工作原理.NFC 通过负载调制的方式工作.这意味着询问器 (PCD) 会发出一个载波磁场，为被动目标 (PICC) 提供能量.有了这个载波场产生的电势，目标就能够解调来自询问器的数据，并通过在这个非常相同的场上调制数据来做出响应.这里的关键是目标永远不会创建自己的字段.
如果您查看 iPhone6 的拆解和零件清单，您会看到有一个非常小的 NFC 环形天线以及在 iPhone6 上实现标签发现.我在
Now that Apple just announced the iPhone 6 will have an NFC chip, does anyone know if iOS 8 will enable reading/detecting RFID tags for the iPhone 6 device? Anyone have any details to share on this?
The iPhone6/6s/6+ are NOT designed to read passive NFC tags (aka Discovery Mode). There's a lot of misinformation on this topic, so I thought to provide some tangible info for developers to consider. The lack of NFC tag read support is not because of software but because of hardware. To understand why, you need to understand how NFC works. NFC works by way of Load Modulation. That means that the interrogator (PCD) emits a carrier magnetic field that energizes the passive target (PICC). With the potential generated by this carrier field, the target then is able to demodulate data coming from the interrogator and respond by modulating data over top of this very same field. The key here is that the target never creates a field of its own.
If you look at the iPhone6 teardown and parts list you will see the presence of a very small NFC loop antenna as well as the use of the AS3923 booster IC. This design was intended for custom microSD or SIM cards to enable mobile phones of old to do payments. This is the type of application where the mobile phone presents a Card Emulated credential to a high power contactless POS terminal. The POS terminal acts as the reader, energizing the iPhone6 with help from the AS3923 chip. The AS3923 block diagram clearly shows how the RX and TX modulation is boosted from a signal presented by a reader device. In other words the iPhone6 is not meant to provide a field, only to react to one. That's why it's design is only meant for NFC Card Emulation and perhaps Peer-2-Peer, but definitely not tag Discovery.
There are some alternatives to achieving tag Discovery with an iPhone6 using HW accessories. I talk about these integrations and how developers can architect solutions in this blog post. Our low power reader designs open interesting opportunities for mobile engagement that few developers are thinking about.
Disclosure: I'm the founder of Flomio, Inc., a TechStars company that delivers proximity ID hardware, software, and services for applications ranging from access control to payments.
Update: This rumor, if true, would open up the possibility for the iPhone to practically support NFC tag Discovery mode. An all glass design would not interfere with the NFC antenna as does the metal back of the current iPhone. We've attempted this design approach --albeit with cheaper materials-- on some of our custom reader designs with success so looking forward to this improvement.
Update: iOS11 has announced support for "NFC reader mode" for iPhone7/7+. Details here. API only supports reading NDEF messages (no ISO7816 APDUs) while an app is in the foreground (no background detection). Due out in the Fall, 2017... check the screenshot from WWDC keynote:
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