BBB Rev C external power supply makes no difference

[kunal.i...@gmail.com]

It is so frustrating to buy this product only to throw it away because external power adaptor (5v, 2A) won't make any difference to USB power supply. I bought Edimax wifi adapator which will remain off even when power is supplied by the adaptor. I cheked Wifi adaptor on my PC and it works. Fool of me to buy a handbook as well:(. Total loss of INR 7000.

[Robert Nelson]

On Fri, Mar 29, 2019 at 6:59 AM <kunal.i...@gmail.com> wrote:
>
> It is so frustrating to buy this product only to throw it away because external power adaptor (5v, 2A) won't make any difference to USB power supply. I bought Edimax wifi adapator which will remain off even when power is supplied by the adaptor. I cheked Wifi adaptor on my PC and it works. Fool of me to buy a handbook as well:(. Total loss of INR 7000.

Your "complaint" is missing vital information, if you actually want help..

sudo /opt/scripts/tools/version.sh

lsusb

Regards,

--
Robert Nelson
https://rcn-ee.com/

[Dennis Lee Bieber]

On Thu, 28 Mar 2019 11:01:36 -0700 (PDT),
kunal.i...@gmail.com declaimed the
following:

WHICH Edimax unit? The first page of their "wireless adapters" page
shows 15 models alone!

USB 2.0 power is limited to 500mA by specification (distributed among
however many ports are on the same hub) -- though many computers are
capable of providing more (especially those with "charging ports"). The
BBB, with a single USB port, likely strictly limits the power to 500mA max.

The 2A power supply doesn't change USB limits (though if you were
powering the board from a USB port, that likely is limited to 500mA coming
in, and since the chip takes some of that, there is less available for USB
out). I'd be curious as to what happens if you use a powered USB hub
between the BBB and the wifi adapter?


--
Wulfraed Dennis Lee Bieber AF6VN
wlf...@ix.netcom.com HTTP://wlfraed.home.netcom.com/

[Will Lin]

Did you ever try "USB Y cable" to supply extra power for your WiFi adapter?

[kunal.i...@gmail.com]

Thanks for prompt reply.

I am using edimax EW 7811UN WiFi adapter. I am powering the device by external power adapter rated 5v 2A. Per my information this should be sufficient for any USB peripheral device. I thought only mini USB port is limited to 500mA. Are both the USB ports limited to 500mA?

Would really appreciate any help.

[Robert Nelson]

The issue isn't power..

Feel free to run these two command and share it's output with the group:

******************************************
sudo /opt/scripts/tools/version.sh

lsusb
******************************************

[Robert Heller]

USB ports are rated for 500ma MAX. That is the *standard* for USB. When you
power the 'Bone from its mini USB port you are only able to provide it with
500ma *total*, so its type-A Host port will have something *LESS* than 500ma
available (500ma less what the BBB itself uses). It is my understanding, that
*UNLIKE* the Raspberry Pi, that to get the full 500ma on the host port, you
need to power the 'Bone from its Coax DC power jack, which can take in the
full 1-2A available from the power supply. The Raspberry Pi's Micro-B "USB"
connection is not really a USB port -- it is only a power connection and you
can shove 1.5 or so amps in that way. This is not the case for the BBB's. Yes,
there are power supplies with "USB" connections that are rated more than
500ma, but that is only meaningfull *if the device you are plugging it into is
specificly "violating" the USB standard* and generally that is only going to
be devices that are not really USB devices, but are just using the USB port as
a power / charging connector, and not as a standard data connection. (Many
smart phones "dual purpose" their USB port as a data connection *and* a charge
port.)

A USB WiFi adapter should not be expecting more than 500ma from the USB port.
NO USB POWERED DEVICE SHOULD EXPECT TO GET MORE THAN 500MA FROM THE USB PORT.
Any USB connected device that needs more power, will have its own power supply
(that is why printers, for example, have power cords, as to many USB connected
external disk drives, CD/DVD/BluRay readers/writers, etc.) [There are the
"exceptions" I mentioned above, but those are obviously special cases.]

>
> Would really appreciate any help.
>

--
Robert Heller -- 978-544-6933
Deepwoods Software -- Custom Software Services
http://www.deepsoft.com/ -- Linux Administration Services
hel...@deepsoft.com -- Webhosting Services

[Dennis Lee Bieber]

On Sat, 30 Mar 2019 15:04:27 -0700 (PDT),
kunal.i...@gmail.com declaimed the
following:

>Thanks for prompt reply.
>
>I am using edimax EW 7811UN WiFi adapter. I am powering the device by external power adapter rated 5v 2A. Per my information this should be sufficient for any USB peripheral device. I thought only mini USB port is limited to 500mA. Are both the USB ports limited to 500mA?
>

The USB 2.0 specification is 500mA per /hub/ distributed over the ports
of the hub ("hub" here include board internal host circuits. Typically if a
computer has more than 4 USB ports, there will be more than one host/hub
[root hub] -- my desktop computer has ports on top, back, and front; and
has three root hubs and three host controllers

https://en.wikipedia.org/wiki/USB_hardware#Power
"""
A bus-powered hub is a high-power device providing low-power ports. It
draws 1 unit load for the hub controller and 1 unit load for each of at
most 4 ports. The hub may also have some non-removable functions in place
of ports. A self-powered hub is a device that provides high-power ports.
Optionally, the hub controller may draw power for its operation as a
low-power device, but all high-power ports draw from the hub's self-power.
"""
{"unit load" is 100mA for USB 2, 150mA for USB 3. By the quoted text, for
an unpowered hub, you have 100mA for the hub, and up to 400mA over four
ports [technically 100mA each port, but I suspect most hubs can feed it to
a single port if only one port is connected]}

I'd repeat my suggestion to try with an external powered hub rated to
deliver up to 500mA per port (this would imply a hub with a 2.5-3A power
supply for four ports). I've actually encountered USB charging adapters
that won't provide enough power to a port to charge a cell phone...