Re: Open hardware AV to digital conversion

From: David Wood <>
Date: Mon, 5 Jan 2015 17:06:11 -0500
Message-ID: <>
On Mon, Jan 5, 2015 at 4:54 PM, Ingo Korb <> wrote:

> Marko Mäkelä <> writes:
> (powering an HDMI source from the sink)
> > Oh, I see. However, let me quote a comment on
> >
> > "A reviewer on Amazon who apparently already has the device (developer I
> > think) says that the device can be powered directly off an HDMI v1.4
> > connector without using the USB power brick.
> I suspect that is a fluke caused by an HDMI sink that applies power to
> the 5V pin even though it should not. When powered from USB the
> Chromecast draws about 300mA with peaks up to 400mA, so it's waaaay
> beyond the 55mA you officially get anyway.
> I'm not really surprised though - there are also quite a few USB hubs
> out there that try to power the computer from their own 5V power brick
> even though that is also the wrong direction.

I wound up with a USB hub that did exactly this.  It had a 9VDC unregulated
brick, no internal regulator, and feedback to the PC.  It fed everything 9
volts.  Good thing I look inside things before I trust them!

PS: don't trust cheap multiport hubs ;)

In the end it's just another case of "don't expect it to work but be
> happy if it does" as well as "be suspicious of the other guy and try to
> make sure that he can't kill you". ;)
> > See for more info
> > about HDMI accessory power requirements."
> >
> > The linked FAQ page says that HDMI-powered devices should offer a
> > fallback of an alternative power supply.
> Yes, but the wording of that FAQ entry seems to suggest to me that it is
> meant only for HDMI sinks that are powered by a source device.
> -ik
>        Message was sent through the cbm-hackers mailing list

       Message was sent through the cbm-hackers mailing list
Received on 2015-01-05 23:00:03

Archive generated by hypermail 2.2.0.