旧的硬件只是坐在那里收集灰尘或妨碍工作，这是令人沮丧的，因此，如果它可以重新调整用途，使之再次有用，那么它是一个令人高兴的原因。今天的超级用户问答文章讨论了为好奇的读者重新利用旧的USB1.1集线器设备的可能性。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

图片由Alexandros Kostalas（Flickr）提供。

问题

超级用户阅读器user1049697想知道是否可以使用旧的USB 1.1集线器为他的设备充电：

I have an old USB 1.1 hub and I was wondering if it could be repurposed for something useful. Would it be possible to connect it to a wall charger that has a built-in USB outlet and use the hub to get 4 USB charging ports? Do USB hubs not work well when connected to wall outlets?

The image below shows a hub similar to the USB 1.1 hub I have:

(Update) I did try this with some devices and the results are as follows:

• My old Android 2.3 device will charge, albeit very slowly.
• My iPhone 5S will not charge at all.

是否可以使用旧的USB 1.1集线器为设备充电？

答案

超级用户贡献者Bob为我们提供了答案：

Unfortunately, it really depends on the specifics of the implementation of both the hub and the device.

The vast majority of simple hubs do not really implement any sort of power control. They will just connect the USB power lines directly to either their host or an external (regulated) power supply, which means you would effectively be sharing the capacity of the power source over all ports.

In practice, however, USB charging gets quite complex. The bottom line is that your USB 1.1 hub will probably charge your peripherals, but at a reduced rate. This is not because the hub is actively limiting the current output, but because peripherals will limit the current they draw unless they can positively confirm the host is capable of supplying that current (to prevent damage to hosts that cannot).

This reduced rate depends on the specific peripheral and the specific hub, but it likely ranges from 100 mA to 500 mA, which is far less than a modern **art phone’s maximum (over 1,000 mA).

To elaborate:

1. If the host implements some kind of power control, then the peripheral must initiate a data connection and negotiate properly. Even though this is technically required by the specs (except the newer battery charging specs), some peripherals might not do so. I imagine most **art phones will at least try, but there are many ‘dumb’ USB peripherals that will not.

2. In the case of a hub connected to a USB power supply without a proper host, it might not work at all.

3. Negotiation is as follows:

• Each peripheral is permitted to draw one unit load without negotiation. Each peripheral should communicate with the host to request more units.
• USB 1.1 and 2.0 define one unit load as 100 mA, with a maximum of 5 unit loads (500 mA).
• USB 3.0 defines one unit load as 150 mA, with a maximum of 6 unit loads (900 mA).

4. Modern devices often need more power (**art phones often draw 1,000 mA – 2,000 mA).

5. There is a battery charging specification that deals with this. Read through the article “How USB Charges Just About Any Electronic Device” for details on how its negotiation and detection works, but that is not too important.

• The charging limit is 1,500 mA, but only if the data lines are shorted together (or respond as if they have been). This is not the case with a data-capable host like a USB hub. There is an additional profile that deals with this, but a USB 1.1 hub probably does not implement it.
• With a non-compatible host, most **arter peripherals will fail to detect a high-capacity source and will therefore fall back to charging at 500 mA at most. This means your USB hub will likely charge the device at a significantly slower rate than plugging the peripheral directly into the charger.

5. There are some other specs such as Apple’s protocol, Qualcomm’s quick charge protocol, etc. They all have their own detection and negotiation methods. They will also not work with a USB 1.1 hub.

6. There is a newer USB Power Delivery spec, but almost nothing implements it yet and it deals with all sorts of wacky things like different voltages.

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