Re: Open hardware AV to digital conversion

Marko Mäkelä <msmakela@gmail.com> writes:

(powering an HDMI source from the sink)

> Oh, I see. However, let me quote a comment on
> http://www.androidauthority.com/chromecast-dongle-official-specs-features-release-date-pricing-248120/
> "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.

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 http://www.hdmi.org/learningcenter/kb.aspx?c=13 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