
An Open Source 4-Port High Power USB Hub - justinclift
https://github.com/dilshan/usb2-power-hub
======
snops
A well documented project, and its admirable getting actual open source
hardware certification, but I think the design isn't really suitable.

All those separate switching regulators look a nightmare for electromagnetic
interference to me, the inductors are unshielded and there is no solid ground
plane on the PCB. I would be surprised if USB HS (480mbps) works reliably with
this layout. Also, there is no consideration given for ESD protection.

A better design would be to have a single more modern high current
regulator/module (the LM2596 [1] used dates from 1999) and use protected high
side load switches to supply the ports. These kind of high current supplies
are a bit tricky (external MOSFETs etc), so a module might be a good shout,
example [2], which might even end up cheaper than having 4 discrete regulators
and passives.

Protected load switches detect overcurrent and turn off the output, sometimes
with auto-retry. Its getting harder to find them in packages with legs, but
the AP22815[3] looks suitable in a TSOT package that shouldn't be any harder
to solder than the USB hub IC.

Protected load switches could also allow removal of the microcontroller, as
they have a simple high/low enable pin and fault LED, that could connect to a
simple slide switch and red/green LED per channel. They also offer nice
features like discharging the output capacitors, and reverse current flow
protection.

As for the suitability/usefulness of a 3A USB hub, if you try and pull 3A
through a USB connector, it will get quite warm, especially if you have a
micro USB connector on the other end.

[1]
[http://www.ti.com/lit/ds/symlink/lm2596.pdf](http://www.ti.com/lit/ds/symlink/lm2596.pdf)
[2] [https://www.digikey.co.uk/product-detail/en/bel-power-
soluti...](https://www.digikey.co.uk/product-detail/en/bel-power-
solutions/SLDN-12D1ALG/179-3029-ND/8028727) [3]
[https://www.digikey.co.uk/product-detail/en/diodes-
incorpora...](https://www.digikey.co.uk/product-detail/en/diodes-
incorporated/AP22815AWT-7/AP22815AWT-7DICT-ND/9562756)

~~~
Iv
I think it would be really great if you slice these criticism into items and
fill in issues!

[https://github.com/dilshan/usb2-power-
hub/issues](https://github.com/dilshan/usb2-power-hub/issues)

That's exactly why such a project benefits from being open source: someone
with enough motivation and knowledge to hack something together do it, then
other people with more specialized knowledge make suggestions for improvement.

~~~
mlyle
Issues aren't really a great way to address core architectural questions that
effectively say "I think it would be better to start over and build this in an
entirely different way".

There are some (small) benefits to independent regulators. A massive rail with
high-side switches is a completely different design approach with its own
benefits.

~~~
Iv
The issue would be tagged "wish" or "for v2" and discussed. It can later be
referenced when a design for a new release is being discussed.

There are always better ways to handle discussions, but on a github issue on
the project's repo is probably better than on a HN thread that won't be linked
to it easily.

------
metafex
Because I see it again and again: Please don't put 20 years old dc/dc
converters into new things. Neither price nor package are valid resons.

There's cheaper and better ones available in similar or the same packages.
E.g. LCSC is a perfectly valid source for many chinese brands and cheaper ICs,
so availability is also not a reason.

Now for the last: familiarity. If you have to take a ti simpleswitcher because
you're scared of DC/DC's, that's also perfectly valid, but again, there are
newer ones which are better all around.

~~~
LeifCarrotson
Is documentation a valid reason?

Old Linear Technology, Analog Devices, and Texas Instruments data sheets were
and are fantastic. Someone with an understanding of little more than the
fundamentals of resistors, inductors, and capacitors could learn about and
implement a DC/DC converter from those docs - and the simplest ones are the
oldest ones.

A seasoned electronics designer with previous examples to draw on can select
an IC and basically reverse-engineer it from the sample application and
comparisons with previous designs they're familiar with. If they get stuck,
they will call their vendor...they might not even read the docs. Hobbyists
can't do that.

~~~
metafex
I have the most experience with TI silicon, so that's where i can talk most
about the datasheets.

Some are excellent, many are really good and except for the odd outlier, most
are sufficient. Especially certain lines of the newer dc/dc's have really good
datasheets where you can just take the reference circuit in the datasheet as
is, plug in your values in the formulas to get your inductance, resistors and
cap values. Oh, and webench power designer also does a good job if your
application is not too complex.

And complexity is also why i mentioned the simpleswitcher series. Other
vendors also have similar simple integrated and modern solutions. With good
documentation.

And as for Linear, they have amazing chips and documentation with a price that
brings tears to your eyes. I have a love/hate relationship with those.

As for calling up vendors, TI at least has their e2e forum where you usually
can get an answer no matter how much you pay them, you just need to create an
account.

~~~
justinclift
Webench Power Designer looks nifty, thanks for pointing it out. :)

------
exabrial
So here's something I'm having a hard time finding. As a musician, I have a
stomp box board. A lot of my effects are digital and reprogrammable. I'd love
to to just "keep them all connected" to a usb hub, then connect a single usb
cable back to my phone or computer.

When doing so, I instantly introduce ground loops. MIDI gets around this by
having opto-isolation as part of the spec, but MIDI-over-USB of course negates
this. I would love to have a USB hub that was opto-isolated for both power,
data, and ground!

~~~
chendragon
USB isolators (single port) can be bought cheaply on eBay but may be bandwidth
limited. They use a small isolated DC-DC brick and a USB isolation chip,
probably with internal isolation capacitors to get the signals across

~~~
mindslight
I think the ADI ones are actually based on transformers.

Specifically they'll do "Full Speed" 12Mbit, but _not_ "High Speed" 480Mbit.
USB3 @ 5Gbit can also be isolated, as it uses separate send/receive pairs. But
that doesn't mean you can use a hub and drop down to 480MBit - they're
separate data paths.

If you need 480Mbit, the best solution is probably a Raspberry Pi or other
SBC, to convert to ethernet.

------
the_biot
It's sad to see so much effort put into making this as open source as
possible, only for the firmware to require Microchip's proprietary MPLAB.

~~~
justinclift
Good point. Still, this seems like a reasonable start.

Being OSS, someone with the right skills / motivation could probably replace
the Microchip pieces with something suitable.

~~~
xondono
Just because this is HN I will drop it, it would not be very difficult to
change it with a ST32XX and do the firmware implementation in Rust

------
hinkley
When I was first playing with Raspberry Pi clones, one of the ways you could
talk to them is over USB, which would have been great for control plane
traffic. I was miffed to find that none of Anker’s products were
simultaneously USB hubs _and_ chargers. I just figured that was a feature.
There are many other options now but at the time I wasn’t satisfied with them
for some reason.

I ended up waiting for later models with more bandwidth before trying again.
Power over USB is a much more compact and reusable pile of equipment.

------
sschueller
I hope Intel or who ever get their USB-C Hub chips out so we can finally get
some USB-C hubs.

~~~
mschuster91
USB-C iirc is USB3 under the hood and can be converted passively from the
"old" to the type-c connectors.

~~~
stormbrew
You can't do Power Delivery over Type-A. Probably there are other thunderbolt-
related functions that don't work either. So yes, you can passively convert to
type-a if what you're doing is within the spec of what type-a can do but it's
not the same as an actual usb type-c hub could be.

~~~
mschuster91
USB-C PD can be done independently of the actual USB (or Thunderbolt, or
DisplayPort alternate modes).

