[PLUG] Powered USB-A hub

[Galen Seitz]

On 1/17/23 09:43, Rich Shepard wrote:
> On Tue, 17 Jan 2023, Galen Seitz wrote:
> 
>> Sorry, I haven't been following this thread too closely, but if this is a
>> device you already own, you can look this up yourself. First use lsusb to
>> find the vendor and product ID values for the USB device of interest. 
>> Then
>> use lsusb again to get more information about the device.
> 
> Galen,
> 
> What a valuable lesson!
> 
> # lsusb -v -d 1235:8211 | egrep 'iProduct|MaxPower'
>    iProduct                3 Scarlett Solo USB
>      MaxPower              500mA
> 
> This suggests to me that a less expensive hub with fewer ports that has at
> least 50W published power would work with all three devices.

FYI, the typical 4 port powered USB 2.0 hub is supplied with a 5V 
adapter that is capable of ~2A, or about 500 mA per port.  With a USB 
3.0 hub where the per port current limit is 900 mA, the max adapter 
current should be higher, but it's unlikely the adapter would be sized 
to allow the max current on every port.

Hubs that have high (>15W) wattage are likely intended to support some 
sort of charging of phones/tablets/etc where communication regarding the 
larger current capability is communicated through a different mechanism.

Once again, the above does not directly apply to USB C hubs that support 
power delivery.

Rich, if you have three devices that draw 500 mA, a hub with a 2A 
adapter should be sufficient.  Look for a hub with a 2.5A or 3A adapter 
if one or two of your devices draw 900 mA.

BTW, I can guarantee you that virtually all of the crazy USB-powered 
things you can buy do *not* have USB descriptors.  Your Ronco USB fan, 
light, and turnip twaddler connect to VUSB (5V) and immediately attempt 
to draw whatever they need, regardless of any intended USB constraints. 
Buyer beware.


galen
-- 
Galen Seitz
galens at seitzassoc.com