Question weird question about vga and hdmi

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Hello,
Not sure where i've to put it so i'll try here ^^ .

My problem is the following:
I'd like to make a cable that can carry both HDMI and VGA signal (not both at the same time) with the minimal amount of connections possible.
In order to do this i plan to use common connections between the VGA input and the HDMI input. Is this possible?
To determine if this is possible I've two questions:
1. What happens to the VGA's signal when the hdmi's one is connected to the screen? is the signal going to the ground or simply not connected to anything...?
If the answer is "pins are just not connected To anything" (n/c not gnd !) then the number of pins needed is the Absolute minimum for an hdmi connection and so :
2. What is the Absolute minimum pins requiered for an hdmi connection ?

Thanks in advance
 

Wesk

Undervolting....
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2. What is the Absolute minimum pins requiered for an hdmi connection ?

"At a minimum you need 8 pins for the data, the clock plus a ground (nine in total). True HDMI has a separate grounds for each data pair, for a total of 12). Connectors must be able to work at 250Mb/s to support lowest HDMI standard video mode 640x480.

You you want to support EDID another couple is needed, with separate ground.

If you want to support hot plug detection another pin is needed. "


Posted by Hamster_nz over at the www.eevblog.com forum:
https://www.eevblog.com/forum/begin...-reduce-the-number-of-pins-required-for-hdmi/
 
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"At a minimum you need 8 pins for the data, the clock plus a ground (nine in total). True HDMI has a separate grounds for each data pair, for a total of 12). Connectors must be able to work at 250Mb/s to support lowest HDMI standard video mode 640x480.

You you want to support EDID another couple is needed, with separate ground.

If you want to support hot plug detection another pin is needed. "


Posted by Hamster_nz over at the www.eevblog.com forum:
https://www.eevblog.com/forum/begin...-reduce-the-number-of-pins-required-for-hdmi/
thanks ! now i need to figure out what happens to the VGA's signal when the hdmi's one is displayed on the screen.
 

Wesk

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You're going to want a switch to isolate the signals, if you run VGA signal voltages to a HDMI port there's a good chance you're going to damage something.
 
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if you run VGA signal voltages to a HDMI port there's a good chance you're going to damage something.
Even if the HDMI isn't the displayed source ? If yes what kind of switch should i need ?
 
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I know this is kind of sidestepping your question, but couldn't you just use a DVI-I cable? Those are intended to carry both an HDMI-type digital signal or an analog VGA signal.
The screen only supports HDMi or VGA, it's for a portable so a little bit too big, and i plan to connect it to a wii (VGA) ou a rpi (HDMI if i don't use a converter which is my last option/solution).
But it was a good idea if only i had tons of space ^^
 
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