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Monday, June 30, 2014

Samsung ARM Chromebook XE303 with VGA adapter - power problems

I have a Samsung ARM Chromebook (the 303 series) which is pretty nice, and I really like it for its size, weight and complete lack of fan and hard drive noise.
Samsung XE303C12-H01DE Chromebook: with 3G modem and
a German keyboard which I'm still not used to.

However, I need to give presentations on occasions.  No problem, I just get one of these:
HDMI to VGA adapter from (SKU 156981)
For less than $10, that's hard to beat.  Unfortunately, I found it doesn't work as-is with the Samsung Chromebook.  Already thinking I need to either give up on the idea of using the Chromebook for presenting or getting a more expensive adapter, I decided to try and see why the bloody thing doesn't work. I verified it does work with my Raspberry Pi, so the problem must be with the Chromebook - perhaps a power problem?  According to Wikipedia, HDMI should have +5V on pin 18.  I opened up the adapter, which can be done with nothing more than one's fingernail, running it along the seam around the VGA socket, then confirmed the absence of 5V on the HDMI port.  Lukily, getting 5V is no problem if you have a USB port nearby and here is my solution to this particular annoyance:
HDMI to VGA adapter with power bypass fitted
I take no responibility for damage you might be inflicting to your Chromebook or any other device you might want to use this mod on. Try this at your own risk, there is a good chance of frying delicate electronics. 
How to solder the power onto the adapter: +5 on
pin 18, ground to wherever convenient.
Basically, take a USB plug and solder two wires to just the outside pins.  Drill a hole through the plastic and the rubber fitting of the HDMI to VGA adapter (slide the insides out first!)  Solder the 5V wire to the pin 18 endpoint of the cable and the ground to a ground point on the adapter PCB.  Done!  I put a knot into the cable for strain relief, to prevent the solder points being ripped off.

That's it! It works nicely, although I don't think the adapter queries the monitor for modes, a decent selection is given to the ChromeOS as soon as the adapter is plugged in.  I've only tried it with one projector so far, but there is no reason it should not work with just about any that accept VGA signals.

Hopefully this information is useful to other (ARM) Chromebook users, but note this is a no-name adapter - yours may look entirely different.  Just remember these adapters are active devices which need power (even if very little), and since the Chromebook isn't delivering it on its HDMI port, you need to get it there somehow.