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Comment by jedberg | Hacker News Reader

That's data transfer only. I want it for my iPad and phone, so I want charging too.

Okay, well that doesn't seem surprising that it wants to be plugged into the wall then (because people will ignore the real limitation on power input from the supply device and complain).

Yup, that's always the answer. The customer doesn't give you the full specs, complains about why this isn't available already. When you deliver your proposed solution it turns out they had some extra physically impossible to fulfill requirements. Reminds me of "The Expert" skit.

The customer is used to being able to plug all of their stuff into a lot standard wall outlet and their headphones in any standard 3.5mm jack so it's not at all surprising that they don't automatically provide all the specs. And frankly customers shouldn't have to care. USB engineers and PMs completely botched the design of USB-C.

I think it’s interesting how a lot of knowledgeable people will chime in on here on certain feature compromises and limitations with USB-C and it always sounds reasonable in isolation. But you only have to take a step back and look at the specification in its totality to see that it’s a shit show. It’s like this thing was designed by a bunch of subcommittees and no one had a clear understanding of or oversight over the big picture.

I am ok with various devices having various capabilities. Not too surprising given they are made from various bits.

But I want one damn cable to bring them all and in the darkness bind them. And a way to know what cable that is.

Well, that exists, it's called Thunderbolt 3 (or 4, since PC makers decided to try to get away with a shitty half-version of TB3).

And the cable exists too, but you have to pay through the nose for it, and people expect all cables to be $5 at Monoprice.

Turns out that 40Gbps and supporting any and all monitors at the same time and 100W of power isn't an easy spec.

Everyone mocked Apple for going with Thunderbolt so early, but it turns out they had it exactly right, just like they did with FireWire, another standard that was super-fast for its time and also included robust power delivery.

Sure, that'll be $129 for a 1.8m cable. Will you be buying one to power your wireless charger? https://www.apple.com/shop/product/MN713AM/A/thunderbolt-4-p...

That's a bit dramatic. It's a longer active cable. You can get a certified passive Thunderbolt 4 cable for 25 Euro including VAT:

http://shop.caldigit.com/eu/Adapters%20And%20Cables/Cables?p...

Short answer to the grandparent: buy a certified Thunderbolt 4 cable. They have clear markings (a Thunderbolt logo, along with the digit 4). They are backwards compatible with Thunderbolt 4, Thunderbolt 3, USB 4, USB 3.2/3.1/3.0, USB-C Gen 1/2, USB 2.0 and can charge 100W.

The customer assuredly cannot do that for a standard wall wallet.

The original poster said they wanted to plug in an iPad and phone for charging. The right comparison would be a customer buying a power strip, plugging in two space heaters at the same time, and wondering why the circuit breaker triggers.

The closer comparison would be a customer wanting a power strip that they can plug multiple phone chargers in to, I think.

A fast-charging phone is to a standard USB port as a space heater is to a standard wall socket.

The promise of usb (any version) is that you could have one port that everything plugs into. Usb-a isn't perfect in that regard, but it's mostly there. Usb-a backslid considerably on that promise.

Okay, but old powered USB hubs were still under $30 and the power cable was optional.

They didn’t provide dozens of watts per port.

I don't need dozens of watts per port. I'm not trying to charge my laptop. I just want to power e.g. a spinning-rust 2.5" external USB hard drive. Which USB ports are able to do at their default line voltage, pre USB-PD negotiation; but which these "data transfer only" USB-C hubs cannot do for some reason.

Not being able to power spinning external drives from USB A ports on laptops is a known issue for a while. Some manufacturers even provided you with a double USB A ports on the laptop side to make sure there is enough power for that.

You're thinking of 3.5" drives. 2.5" drives are a bit easier to power.

It wasn't intentional on my part, but it appears the hub I link will provide 3.5 watts of power to each port:

https://support.satechi.com/hc/en-us/articles/4405450897435-...

And I'm again not familiar with power requirements for external drives, but it appears that is sufficient for at least some 2.5" USB drives?

So you want to get 4 × 10W out of a single 2.5W (at most 10W) upstream port?

From what I've read the MacBook can output 15W on a port, so I'd expect a hub to be able to output 15W when one device is plugged in, 10W+5W with two, etc.

Not having ports with constant capabilities is a source of customer dissatisfaction when devices work when plugged in independently but not together.

Consider for instance the new 14" and 16" MacBook pros: They got rid of the 4th Thunderbolt port in favor of an HDMI port, likely because of internal bandwith constraints. They could have kept Thunderbolt and HDMI, and only have one Thunderbolt port on the right side work when HDMI is plugged in, but they didn't, because having your external drive work only when your monitor is unplugged is unintuitive.

They were right originally when then went usb-c only. You could output hdmi on any port or do anything else with the port. We had gotten to the point where most offices had a usb-c adapter on the end of every loose hdmi cable so it wasn't an issue.

You mean Thunderbolt only. Not USB-C. Let's credit Apple for what they actually did, which was to go with the non-shitty port from the beginning even though it was expensive and everyone mocked them for doing so.

doesnt §4.6 of the USB-C spec show the precedence of power source usage? I.E. there is no 10W option, just 3A, 1.5A, 0.9A, 0.5A at 5V or 15W, 7.5W, 4.5W, or 2.5W. so then your 15W port turns into 2x 7.5W ports or 3x 5W ports. I dont know if you can count on the upstream port being 15W. if its 7.5W do you do 4.5+2.5W and 3x 2.5W?

also, I've found that no one obeys the current limit for inrush so now your downstream ports have to allow 7.5+W until they enumerate and you can lower the current limit.

additionally, people are complaining about not being able to tell cables apart. can they tell the power requirements and calculate how much power a combination of devices requires?

Those are only for dumb power supplies using resistors to signal max amount. Negotiated power is very granular.

> additionally, people are complaining about not being able to tell cables apart. can they tell the power requirements and calculate how much power a combination of devices requires?

If they don't know device power levels they can just learn what can simultaneously go on a single port when they try, like with USB 2.

The macbook is using thunderbolt, not pure usb-c.

Note that these terms are not strictly comparable. USB-C is just a connector specification. There are many protocols that utilize USB-C: USB 3.2, USB4 and Thunderbolt being some of them.

This is also a good point. Even I use the terms interchangeably when I shouldn't, and I should know better.

At most 10W?

2A at 5V is the maximum you can get without USB-PD. 500mA 5V is the maximum that’s guaranteed.

Why are we assuming no PD?

Spendy but capable-looking: https://plugable.com/products/usb4-hub3a (I haven't tried it, but I have had good luck with some of their other products, they take Linux support a little more seriously than most... though not on this hub, apparently...)

That's the issue really. There are so many features that you will never get a device that does exactly what you want and no more. So you either get the basic usb3 only or you get the fully featured thunderbolt dock which costs a lot.

I’m pretty sure for my 7 port usb-a hub (usb 3) I have to plug it into the wall power too. My max pro doesn’t send enough current to to hub so if I want to to be power stable I have to supply extra power…

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