EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: step_s on November 12, 2016, 03:35:45 pm
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Hi EEVers
I made a screen from an old labtop LCD and the MT6820-D monitor driver, and it works like it should when run over VGA.
I then tried hooking it up to my main computer through a passive HDMI to VGA converter, and this makes the screen turn on for 1sec with the desktop showing, then goes black, and shows "no signal" for a couple of seconds, then just loops like this.
The converter works without problems with a normal VGA compatible screen.
So the home made screen works, and the converter works, but they don't work together :/
Any thoughts? Could the passive converter trip the monitor driver chip in some way?
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HDMI signals are digital 0's, and 1's. VGA is Analog. With the right converter, maybe it works...? :-//
You might have HDCP issues as well if you try displaying copyrighted material.
http://www.tomshardware.com/forum/id-3133491/hdmi-vga-converter-work.html (http://www.tomshardware.com/forum/id-3133491/hdmi-vga-converter-work.html)
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Oh and don't forget that many cheap HDMI->VGA converters take power from the HDMI connector intended to drive the EDID EEPROMs in monitors/TVs (there is no such thing as "passive" HDMI to VGA converter). The amount of current available on these ports is often insufficient and the problems you have could be well thanks to that.
This is a typical example of such converter:
https://www.aliexpress.com/item/HDMI-to-VGA-Cable-HDMI-Male-to-VGA-Female-HDMI-to-VGA-Video-Converter-Adapter-Cables/32722750678.html (https://www.aliexpress.com/item/HDMI-to-VGA-Cable-HDMI-Male-to-VGA-Female-HDMI-to-VGA-Video-Converter-Adapter-Cables/32722750678.html)
Most HDMI ports will not be able to deliver the amount of current this thing needs and you could even fry your device with it. I have hacked one of these to give it external power from a nearby USB port, then it worked OK (well the image quality sucks, but you get what you pay for).