The impossible dream of USB-C

USB-C 之白日梦
未经作者 Marco Arment 许可转载
原文链接：https://marco.org/2017/10/14/impossible-dream-of-usb-c

I love the idea of USB-C: one port and one cable that can replace all other ports and cables. It sounds so simple, straightforward, and unified. In practice, it’s not even close.

我喜欢 USB-C 这个设计：一种端口，一条线缆就可以取代其他各种各样的线缆，听起来很简单，直接，统一，但是实际使用中，一点也不。

USB-C normally transfers data by the USB protocol, but it also supports Thunderbolt… sometimes. The 12-inch MacBook has a USB-C port, but it doesn’t support Thunderbolt at all. All other modern MacBook models support Thunderbolt over their USB-C ports… but if you have a 13-inch model, and it has a Touch Bar, then the right-side ports don’t have full Thunderbolt bandwidth.

通常 USB-C 通过 USB 协议传输数据，部分支持 Thunderbolt，12 寸 MacBook 仅有的 USB-C 接口却完全不支持 Thunderbolt，其他具备 USB-C 接口的 MacBook Pro 却支持 Thunderbolt. 然而你有一台13寸具备 TouchBar 功能的 MacBook Pro，右边的 USB-C 接口却不能完全发挥 Thunderbolt 接口的带宽（数据传输速率），好气啊。

If you bought a USB-C cable, it might support Thunderbolt, or it might not. There’s no way to tell by looking at it. There’s usually no way to tell whether a given USB-C device requires Thunderbolt, either — you just need to plug it in and see if it works.

如果你购买了一条 USB-C 线缆，只看外观是无法判断是否支持 Thunderbolt ，同样的也无法知道一台 USB-C 接口的设备是否支持 Thunderbolt，只有将线缆接入设备才可以知晓。

Much of USB-C’s awesome capability comes from Thunderbolt and other Alternate Modes. But due to their potential bandwidth demands, computers can’t have very many USB-C ports, making it especially wasteful to lose one to a laptop’s own power cable. The severe port shortage, along with the need to connect to non-USB-C devices, inevitably leads many people to need annoying, inelegant, and expensive dongles and hubs.

USB-C 的主要卖点是支持 Thunderbolt 和其他的交替模式。考虑到潜在的带宽需求和节省成本的前提，通常计算机不会配备较多的USB-C 接口。有限的接口，庞大的连接非 USB-C 设备的需求，用户必须去购买烦人的，不优雅的，昂贵的转接线和Hub.

While a wide variety of USB-C dongles are available, most use the same handful of unreliable, mediocre chips inside. Some USB-A dongles make Wi-Fi drop on MacBook Pros. Some USB-A devices don’t work properly when adapted to USB-C, or only work in certain ports. Some devices only work when plugged directly into a laptop’s precious few USB-C ports, rather than any hubs or dongles. And reliable HDMI output seems nearly impossible in practice.

市场上可以购买到的 USB-C 转接线，通常使用的是可靠性不高，普通的芯片。一些 USB-A 转接线会导致 MacBook Pro 无法使用Wi-Fi, 一些 USB-A 设备无法正常使用或者仅能使用在指定的端口。一些设备仅能使用在计算机内置的 USB-C 端口，无法使用在任何外接转接设备，实际使用中 HDMI 输出也是不可能的。

Very few hubs exist to add more USB-C ports, so if you have more than a few peripherals, you can’t just replace all of their cables with USB-C versions. You’ll need a hub that provides multiple USB-A ports instead, and you’ll need to keep your USB-A cables for when you’re plugged into the hub — but also keep USB-C cables or dongles around for everything you might ever need to plug directly into the computer’s ports.

市面上的 Hub 很少拥有多个 USB-C 端口，因此当你使用一些外接设备时，你也不能全部用 USB-C 线缆进行替代。 因此用户仍然需要一个配备较多 USB-A 接口的 Hub, 因此 USB-A 的线缆也不能扔掉，同时还需要标配一些 USB-C 线缆或者转接线，以便需要的时候可以直接接入电脑的端口。

Hubs with additional USB-C ports might pass Thunderbolt through to them, but usually don’t. Sometimes, they add a USB-C port that can only be used for power passthrough. Many hubs with power passthrough have lower wattage limits than a 13-inch or 15-inch laptop needs.

配备 USB-C 接口的 Hub 主要用来供电，但是通常不能。有时，增加的USB-C端口专门用于供电，但是大部分具备供电功能的Hub 的充电功功率通常小于13寸或者15寸笔电所需的充电功率。

Fortunately, USB-C is a great charging standard. Well, it’s more of a collection of standards. USB-C devices can charge via the slow old USB rates, but for higher-powered devices or faster charging, that’s not enough current.

好消息是，USB-C是一个杰出的充电标准，也是多个标准的集合体。USB-C 设备不仅支持缓慢的USB充电协议，也支持更高功率的设备或者快充。

Many Android phones support Qualcomm’s Quick Charge over USB-C, which is different — usually — from the official, better, newer USB-C Power Delivery (PD) standard. Apple products, some Android phones, and the Nintendo Switch use USB-C PD. Quick Charge devices don’t get any benefit — usually — from PD chargers, and vice versa.

许多 USB-C 接口的安卓手机，使用的是高通的快充协议，苹果产品，一些安卓手机，任天堂的 Switch 使用的是近期更新，效率更高的 USB-C PD。支持高通快充的设备使用PD充电器时无法实现快充，反之也是一样

Your charger, cable, and any standalone batteries you want to use all must support the same charging standard for it to work at full speed.

如果要达到最高的充电效率，使用的充电器，线缆或者独立的移动电源与对应的硬件必须支持相同的充电协议。

Some cables don’t support USB-C PD at all, and most don’t support laptop wattages. Apple’s cable supports USB-C PD charging at high wattages… unless you bought the earlier version that doesn’t. Most standalone batteries sold to date don’t support USB-C PD — there are only a handful on the market so far, and most of them can’t charge a laptop at full speed, unless it’s the 12-inch MacBook.

一些线缆完全不支持 USB-C PD 标准，大部分的线缆也不支持笔记本供电。苹果的线缆支持 USB-C PD 以高功率的方式充电，除非你购买的是早期版本的线缆。 市面上的大部分外置电源不支持 USB-C PD, 仅有的几款支持 USB-PD 产品也只能实现为 12 寸的 MacBook 全速充电。

You can use USB-C PD to fast-charge an iPhone 8 or iPad Pro with a USB-C to Lightning cable. But it doesn’t work with every USB-PD battery or charger, or every USB-C to Lightning cable, or every iPad Pro.

你可以使用支持PD协议的充电器，以及USB-C Lightnings 数据线实现 iPhone 8或者iPad Pro 的快充功能，但是并不意味着任何一个USB PD电源，充电器，都可以实现快充。

And, of course, there’s usually no way to tell at a glance whether a given cable, charger, battery, or device supports USB-C PD or at what wattages.

当然，谁也无法一眼看出线缆/充电器/电池/对应设备是否支持USB-PD 或者以多大的功率进行充电。

It’s comforting to think that over time, this will all settle down and we’ll finally achieve the dream of a single cable and port for everything. But that’s not how technology really works.

假如有一天，所有的问题都被解决了，我们终于实现了一个端口，一条线缆走天下的梦想，那是多么美好，但那不是科学技术真正的运转方式。

Before today’s USB-C can become ubiquitous and homogeneous, the next protocol or port will come out. We’ll have new, faster USB 4.0 and Thunderbolt 4 standards over the same-looking USB-C ports. We’ll want to move to an even thinner USB-D port. The press will call it “the future” and Apple will celebrate its new laptops that only have a USB-D port — two, if we’re lucky.

也许在 USB-C 变得流行之前，新的传输协议或者端口已经产生了，同样外观的 USB-C 端口支持了更新更快的 USB4.0 和 ThunderBolt 4。我们也许将会进入可以称之为未来的更加纤薄的 USB-D 端口的时代，那时苹果发布的新款 Mac 将会只有一个 USB-D端口，如果足够幸运的话，会是两个。

And we’ll have to start over again, buying all new cables, dongles, hubs, chargers, batteries, and displays to adapt it to what we really need.
那时所有的问题将会再次重现，购买新的线缆，转接线，Hub，充电器，电池，视频转接线等。

Maybe next time, we’ll get it right. But probably not.

也许下次，我们会得到正确的，但是也有可能不会。