echopleks
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Joined: Mon May 06, 2013 3:04 am

*Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 3:19 am

As the title says, I have a VGA-to-HDMI adapter that has its own power supply:

http://www.ebay.com/itm/New-Audio-VGA-t ... 2a1f16542f

I've been trying different power supplies and USB cords to power the Pi itself, but finally realized that it's the display adapter that's causing my woes. I unplugged my USB keyboard and left the USB Wifi Dongle (http://www.tp-link.com/ca/products/deta ... =TL-WN725N) and power plugged in.

If I have the keyboard, USB wifi, and HDMI (to adapter) plugged in, everything functions well *except* wifi connectivity. Unplug the keyboard, still no connectivity. Unplug the HDMI cord and BAM! - SSH in no problem at all.

So, given that I'm not too eager to try my luck with another VGA-to-HDMI adapter (or wifi dongle - listed as working w/o powered USB hub on elinux), I'm hoping there might be setting(s) I'm unaware of that could help remedy this?

I don't have a multimeter to use atm, but happy to provide any/all logs that may be of use. I'm also willing to accept the blunt truth that I may be SOL with any piece of hardware, but would prefer that type of message if it's close to 100% positive.

Many thanks!

EDIT; more details: Model B board. Currently running Raspbmc but experienced issues with openelec and Xbian as well.

obcd
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Re: *Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 6:59 am

The thing you are showing on Ebay is a convertor from VGA to HDMI. I have no idea how you can use such on the Pi.
Assuming you want to connect your Pi to an Analog Vga screen, you will need a HDMI to VGA adapter which converts the other way around.
There is no setting that will make it work automagically.

echopleks
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Joined: Mon May 06, 2013 3:04 am

Re: *Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 3:03 pm

obcd wrote:The thing you are showing on Ebay is a convertor from VGA to HDMI. I have no idea how you can use such on the Pi.
Assuming you want to connect your Pi to an Analog Vga screen, you will need a HDMI to VGA adapter which converts the other way around.
There is no setting that will make it work automagically.
While I appreciate the response, I think you're assuming too much about that converter. The converter works both ways despite being marketed as VGA-to-HDMI.

As stated in my post, the converter works with the Pi (full res picture, audio) - it just seems to draw a *little* too much power or something to cause issues with wifi. Tested with my computer that has HDMI out and the converter also worked perfectly. I don't have the page or post handy, but I did select that converter based on more than one person having success using it with the Pi. Just trying to figure out where my misstep is!

obcd
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Re: *Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 4:27 pm

A poor quality hdmi cable can cause interference with the wifi adapter.
Another thing you do is actually grounding the Pi when you connect it to the monitor.
There is one pin on the hdmi connector that can draw current, but if it's drawing 2 much it will fry a diode on the Pi. If a video convertor has it's own supply, it normally get's it's power from there.
The way it's displayed on Ebay with VGA to HDMI written on the box and the way the connectors are marked as VGA in, AUDIO IN and HDMI OUT, I surely wouldn't expect it to work in both directions.

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mahjongg
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Re: *Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 4:30 pm

echopleks wrote: While I appreciate the response, I think you're assuming too much about that converter. The converter works both ways despite being marketed as VGA-to-HDMI.
It is that you claim that its working, or I would never guessed! Its technically almost impossible for such an adapter to "work both ways", and it is labeled very clearly VGA IN and HDMI OUT. Is there a switch on that box that is used to switch it from HDMI=>VGA to VGA=>HDMI I wonder?

Anyway, if I am forced to conclude it seems to work, then it seems that even though it has its own power supply the adapter still seems to draw power from the PI, which is bizarre because it would only do that if the PSU of the converter outputs at least 0.2V less than the PSU of the PI (due to the diode in the PI).

Maybe that removing the diode of the PI (D1) will help against that. Or maybe the PSU of the adapter is failing to deliver 5.0V.

Also whenever you are NOT connecting a real HDMI device, the PI cannot read out the monitor specifications of the (HDMI) monitor, so its necessary to edit config.txt to set a specific display resolution the PI will then use.

echopleks
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Joined: Mon May 06, 2013 3:04 am

Re: *Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 4:46 pm

obcd wrote:A poor quality hdmi cable can cause interference with the wifi adapter.
Another thing you do is actually grounding the Pi when you connect it to the monitor.
Thanks! I will try another HDMI cable this evening and if that doesn't help, look into grounding the Pi.
mahjongg wrote:It is that you claim that its working, or I would never guessed! Its technically almost impossible for such an adapter to "work both ways", and it is labeled very clearly VGA IN and HDMI OUT. Is there a switch on that box that is used to switch it from HDMI=>VGA to VGA=>HDMI I wonder?
This could be a case of "not exactly as pictured", but I feel that even if I checked tonight, the box would still likely have the labels. Only reason I purchased was seeing other success stories (of which I'll have to dig up and see if I can get answers from those folks!)

MaxK1
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Re: *Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 5:22 pm

Another thing worth trying is a USB extension cable to get the WiFi dongle further away from the adaptor and/or HDMI cable.
You are in a maze of twisty little passages, all alike.
When General Failure and Major Disaster get together, Private Parts usually suffers.

echopleks
Posts: 4
Joined: Mon May 06, 2013 3:04 am

Re: *Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 6:22 pm

MaxK1 wrote:Another thing worth trying is a USB extension cable to get the WiFi dongle further away from the adaptor and/or HDMI cable.
Never considered that. Would the theory be that it could mitigate or eliminate any potential interference that the HDMI connection is causing? Will definitely give it a try tonight; thanks!

MaxK1
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Joined: Sun Aug 26, 2012 11:34 pm

Re: *Powered* VGA-to-HDMI Drawing Power - Can Settings Help?

Mon May 06, 2013 6:33 pm

*If* it's interference, maybe. It did help in at least one case. Whether it was truly interference or just "a bad spot" I don't know... ;-)
You are in a maze of twisty little passages, all alike.
When General Failure and Major Disaster get together, Private Parts usually suffers.

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