Turning My CASIO F-91W Into a Contactless Payment Device

将我的卡西欧 F-91W 改造成非接触式支付设备

PREFACE Recently I have been travelling quite a bit and I could appreciate the fact to pay for bus/metro rides or coffee/beers around just with contactless technology. Apple/Google/Samsung-Pay based systems require actively unlocking your tech device and this generates some slow-down in the payment process. If you’re standing in line with a bunch of people behind you awaiting and something goes wrong, you’re toast 🥪.

前言 最近我经常出差，我非常欣赏只需通过非接触式技术就能支付公交/地铁费用或购买咖啡/啤酒的便捷。基于 Apple/Google/Samsung-Pay 的系统需要主动解锁你的电子设备，这在支付过程中会产生一定的延迟。如果你正排在长队中，身后有一群人等着，而支付过程出了差错，那你就彻底完蛋了 🥪。

As an inveterate NERD, I’ve worn a CASIO F-91W since I still had pimples on my face. This legendary timepiece graces the wrists of tech aficionados worldwide with its sleek design, sturdy build, and impressive battery life (is said to last ~ 7 years). It became a symbol of the digital watch revolution starting from the 80’s with the quartz adoption. I thought it would be nice not to have to take out my credit/debit card from the wallet or my mobile phone from the pocket to pay, but instead, to bring the watch closer to the PoS and just pay with a pinch of modern-day magic ✨. So I decided to give it a new life and take it to the next level by combining nostalgia and innovation in pure hacking style.

作为一个资深极客，我从青春期长痘痘的时候就开始佩戴卡西欧 F-91W 了。这款传奇时计凭借其时尚的设计、坚固的结构和令人印象深刻的电池寿命（据说可续航约 7 年），点缀着全球科技爱好者的手腕。它成为了 80 年代石英表普及以来数字手表革命的象征。我想，如果不用从钱包里掏出信用卡/借记卡，也不用从口袋里掏出手机来支付，而是直接把手表靠近 POS 机，用一点现代科技的“魔法” ✨ 来完成支付，那该多好。于是，我决定通过这种纯粹的黑客方式，将怀旧与创新结合起来，赋予它新的生命，并将其提升到一个新的水平。

ANALYSIS The NFC (Near Field Communication) technology enables an exchange of information without direct physical contact between two devices involved. In the case of contactless payment cards, they can be used without being inserted in a PoS slot or by entering a PIN code, making financial transactions faster and more convenient.

分析 NFC（近场通信）技术能够在两个设备之间进行信息交换，而无需直接物理接触。对于非接触式支付卡，它们无需插入 POS 机插槽或输入 PIN 码即可使用，这使得金融交易更加快捷和方便。

Inside a plastic (or metallic) contactless payment card, we can find several components: Microchip: often referred to as a secure integrated circuit (IC) chip or a smart chip, it serves as the brain of the card and contains various sub-components like the CPU, the Memory, and a Crypto Core. Antenna: usually made of copper or aluminum, is responsible for transmitting and receiving radio frequency signals to enable contactless communication.

在塑料（或金属）非接触式支付卡内部，我们可以找到几个组件： 微芯片：通常被称为安全集成电路 (IC) 芯片或智能芯片，它是卡片的大脑，包含 CPU、内存和加密核心等各种子组件。 天线：通常由铜或铝制成，负责发送和接收射频信号，以实现非接触式通信。

Payment cards are passive devices that do not require their own power source. Instead, they are powered by electromagnetic induction when they come into proximity with an active NFC device, such as a smartphone or a contactless payment terminal. The active NFC device generates a magnetic field, which induces a current in the NFC’s target device antenna. This induced current provides enough power to activate it by allowing it to operate and communicate with the active device.

支付卡属于无源设备，不需要自带电源。相反，当它们靠近智能手机或非接触式支付终端等有源 NFC 设备时，会通过电磁感应获得电力。有源 NFC 设备产生磁场，在 NFC 目标设备的天线中感应出电流。这种感应电流提供了足够的能量来激活设备，使其能够运行并与有源设备进行通信。

New payment cards technology consists in a dual interface that doesn’t need any wired contacts between the microchip and the antenna modules. The antenna in the card body has a few additional turns around the area where the chip module is embedded. This card body antenna inductively couples into a tiny loop antenna that is directly integrated into the microchip module. This simplifies the card production process as the antenna does not need to be attached (e.g. glued, welded or soldered) to the chip module.

新型支付卡技术采用双界面设计，微芯片和天线模块之间无需任何有线连接。卡体内的天线在芯片模块嵌入区域周围多绕了几圈。这种卡体天线通过电磁感应耦合到直接集成在微芯片模块中的微型环形天线上。这简化了卡片的生产过程，因为天线无需（通过胶水、焊接或锡焊）固定在芯片模块上。

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