
Open source USB Type-C to HDMI Adapter - mmastrac
http://www.chromium.org/chromium-os/hoho
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tlb
This is interesting, because lots of cheap clones of the adapter will appear
and quickly drive the market price below $5.

There has been a dichotomy for several years: generic adapters are $2-$5,
while proprietary adapters are $20-$50. It's not due to the BOM cost of the
chip, which is probably less than the cost of the copper. This might be the
first mainstream adapter with a chip, other than PL2302-based USB-serial
adapters, that are cheap.

~~~
lucaspiller
You can already get a wide range of Chinese clones of proprietary Apple
adapters for under $3:

[http://m.ebay.com/itm/131250380700](http://m.ebay.com/itm/131250380700)

[http://m.ebay.com/itm/111573913018](http://m.ebay.com/itm/111573913018)

Some are actually better than Apple, the braided lightning cables are a lot
harder to break. You can even get them with LEDs if that's you thing.

In my experience they work just as well, but quality can sometimes really
vary. I hope this leads to cheap clones from reputable manufacturers who have
high quality standards.

~~~
walterbell
Are there affordable active converters from (mini) Displayport to dual-link
DVI? These cost $95 from Apple.

~~~
giarc
$71 From Monoprice

[http://www.monoprice.com/Product?c_id=104&cp_id=10428&cs_id=...](http://www.monoprice.com/Product?c_id=104&cp_id=10428&cs_id=1042802&p_id=6904&seq=1&format=2)

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vsampath
For what it's worth, this appears to be an active dongle using a MegaChips
device to do the DisplayPort to HDMI 2.0 conversion. USB Type-C alternate mode
handles the passing of DisplayPort audio/video data from the GPU over the USB
pins (ML0-3), and the MegaChips device converts that to HDMI 2.0 TMDS
signaling.

~~~
lsaferite
Do you have a link to the datasheet for the DP-HDMI2 chip?

I tried searching based on the part number and apparently my google-fu was
weak.

~~~
vsampath
No, my Google-fu also failed me. There's also an SPI ROM that is an input into
the DP-HDMI2 chip, so there's likely firmware there that is not part of
Google's open-sourcing.

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tdicola
Is there a layout yet or is it just a schematic? From what I understand USB
3.0 is so crazy fast it requires quite a bit of RF magic/knowledge to even
just route from the connector to a chip on a board.

~~~
platinum1
Yep, not to mention the manufacturing technologies required to meet the length
matching and impedance targets. It's probably not realistic for hobbyist
projects. I think this is mostly useful as a reference for making other types
of adapters that might only need to use USB 2.0, but still need the
microcontroller to negotiate the Type C stuff.

edit: There are two other open source Type C projects (and they stick with the
Hostess snack theme):

[http://www.chromium.org/chromium-
os/twinkie](http://www.chromium.org/chromium-os/twinkie)

[http://www.chromium.org/chromium-
os/dingdong](http://www.chromium.org/chromium-os/dingdong)

~~~
nknighthb
At what point do consumer devices start using internal optical interconnects?

~~~
rcfox
While not usually meant for carrying high-speed signals, there are optical
isolators[0] that are used to communicate between circuits that are not
connected electrically.

I'd guess that fiber optics is only a net win over large enough distances that
you make up the latency from converting electrics signals to optical and back.

[0] [http://en.wikipedia.org/wiki/Opto-
isolator](http://en.wikipedia.org/wiki/Opto-isolator)

~~~
raverbashing
These are most for electrical insulation, not high speed (most probably aren't
made for high speed)

It's a whole different problem to have even a short distance connection go up
to GHz speeds.

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rcfox
While the firmware may be open source, the hardware is not. It's not enough to
be able to see the schematic in a PDF; it's important to have proper, machine-
readable, design files.

Nobody would consider a print-out of the Linux kernel's source code to be an
acceptable means of distributing it.

~~~
rosser
_Nobody would consider a print-out of the Linux kernel 's source code to be an
acceptable means of distributing it._

To the contrary, bound and printed copies of the PGP source code were used to
get around ITAR export controls on crypto in the '90s.

[https://en.wikipedia.org/wiki/Pretty_Good_Privacy#Criminal_i...](https://en.wikipedia.org/wiki/Pretty_Good_Privacy#Criminal_investigation)

~~~
aroman
Wow, that's crazy! I've always wondered if something like that would be
feasible... had no idea it had actually been done on a grand-scale before.
Thanks for that.

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gima
I'm quite a newbie with electronics, but the workhorse of this device seems to
be a chip named "MCDP2850", and I can't seem to find this chip anywhere. I've
also encountered this kind of "failure to find chips pertaining to
DisplayPort/HDMI/DVI" before. How do people find these chips - both when
designing - and as hobbyist who needs the chip?

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swamp40
So, why do these guys design things and then just give all the files away on
the internet?

Or is my midwestern-ness showing?

