USB-C 之白日夢
未經作者 Marco Arment 許可轉載
原文鏈接：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.

我喜歡 USB-C 這個設計：一種端口，一條線纜就可以取代其他各種各樣的線纜，聽起來很簡單，直接，統一，但是實際使用中，一點也不。

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 通過 USB 協議傳輸數據，部分支持 Thunderbolt，12 寸 MacBook 僅有的 USB-C 接口卻完全不支持 Thunderbolt，其他具備 USB-C 接口的 MacBook Pro 卻支持 Thunderbolt. 然而你有一臺13寸具備 TouchBar 功能的 MacBook Pro，右邊的 USB-C 接口卻不能完全發揮 Thunderbolt 接口的帶寬（數據傳輸速率），好氣啊。

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.

如果你購買了一條 USB-C 線纜，只看外觀是無法判斷是否支持 Thunderbolt ，同樣的也無法知道一臺 USB-C 接口的設備是否支持 Thunderbolt，只有將線纜接入設備才可以知曉。

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 的主要賣點是支持 Thunderbolt 和其他的交替模式。考慮到潛在的帶寬需求和節省成本的前提，通常計算機不會配備較多的USB-C 接口。有限的接口，龐大的連接非 USB-C 設備的需求，用戶必須去購買煩人的，不優雅的，昂貴的轉接線和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.

市場上可以購買到的 USB-C 轉接線，通常使用的是可靠性不高，普通的芯片。一些 USB-A 轉接線會導致 MacBook Pro 無法使用Wi-Fi, 一些 USB-A 設備無法正常使用或者僅能使用在指定的端口。一些設備僅能使用在計算機內置的 USB-C 端口，無法使用在任何外接轉接設備，實際使用中 HDMI 輸出也是不可能的。

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 很少擁有多個 USB-C 端口，因此當你使用一些外接設備時，你也不能全部用 USB-C 線纜進行替代。 因此用戶仍然需要一個配備較多 USB-A 接口的 Hub, 因此 USB-A 的線纜也不能扔掉，同時還需要標配一些 USB-C 線纜或者轉接線，以便需要的時候可以直接接入電腦的端口。

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.

配備 USB-C 接口的 Hub 主要用來供電，但是通常不能。有時，增加的USB-C端口專門用于供電，但是大部分具備供電功能的Hub 的充電功功率通常小于13寸或者15寸筆電所需的充電功率。

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是一個杰出的充電標準，也是多個標準的集合體。USB-C 設備不僅支持緩慢的USB充電協議，也支持更高功率的設備或者快充。

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.

許多 USB-C 接口的安卓手機，使用的是高通的快充協議，蘋果產品，一些安卓手機，任天堂的 Switch 使用的是近期更新，效率更高的 USB-C PD。支持高通快充的設備使用PD充電器時無法實現快充，反之也是一樣

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.

如果要達到最高的充電效率，使用的充電器，線纜或者獨立的移動電源與對應的硬件必須支持相同的充電協議。

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.

一些線纜完全不支持 USB-C PD 標準，大部分的線纜也不支持筆記本供電。蘋果的線纜支持 USB-C PD 以高功率的方式充電，除非你購買的是早期版本的線纜。 市面上的大部分外置電源不支持 USB-C PD, 僅有的幾款支持 USB-PD 產品也只能實現為 12 寸的 MacBook 全速充電。

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協議的充電器，以及USB-C Lightnings 數據線實現 iPhone 8或者iPad Pro 的快充功能，但是并不意味著任何一個USB PD電源，充電器，都可以實現快充。

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.

當然，誰也無法一眼看出線纜/充電器/電池/對應設備是否支持USB-PD 或者以多大的功率進行充電。

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，所有的問題都被解決了，我們終于實現了一個端口，一條線纜走天下的夢想，那是多么美好，但那不是科學技術真正的運轉方式。

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.

也許在 USB-C 變得流行之前，新的傳輸協議或者端口已經產生了，同樣外觀的 USB-C 端口支持了更新更快的 USB4.0 和 ThunderBolt 4。我們也許將會進入可以稱之為未來的更加纖薄的 USB-D 端口的時代，那時蘋果發布的新款 Mac 將會只有一個 USB-D端口，如果足夠幸運的話，會是兩個。

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.
那時所有的問題將會再次重現，購買新的線纜，轉接線，Hub，充電器，電池，視頻轉接線等。

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

也許下次，我們會得到正確的，但是也有可能不會。