Author Topic: Home Made DVI-I to VGA/HDMI Converter Possible?  (Read 408 times)

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Offline Mechatrommer

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Home Made DVI-I to VGA/HDMI Converter Possible?
« on: September 18, 2019, 12:38:42 pm »
i tried to search internet but it seems no one has done this or my google-foo is failing. or maybe i'm missing something because such adapter is so simple its like nothing inside there. the point for home made because i have a bunch of DVI-DVI connectors and VGA-VGA connectors so i think maybe i can reuse them? i know its cheap but ordering it will take days to arrive and i need this tonight or tomorrow if possible. i have new (used) workstation arrived its blank and i need it windows installed but didnt realize the display card only has DVI-I and DisplayPort dough, i only have monitors with VGA or HDMI input. if possible send me diagram, if not possible tell me why? and how that innocent off the shelf DVI-VGA dongle is made? thanks.
« Last Edit: September 22, 2019, 06:41:52 pm by Mechatrommer »
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Offline Mechatrommer

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #1 on: September 18, 2019, 12:51:56 pm »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline janoc

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #2 on: September 18, 2019, 02:01:50 pm »
That looks legit but the question is to why bother with this? These adapters come packed with every graphic card, motherboard and what not these days (VGA outputs are getting rare, most cards have one or two DVIs and then only HDMI/DisplayPort connectors). I have probably 3-4 of them sitting in my desk, unused, because these are so rarely needed.

And if you don't have one, they can be bought for a buck or two, delivered. Also most stores selling computers will have adapters like this.

Building this yourself can be a pain because if you aren't careful with shielding and soldering you are going to have signal integrity issues - noise, ghosting due to reflections, messed up colors, etc. Can be done, though.
 
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Online ogden

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #3 on: September 18, 2019, 02:22:07 pm »
I have probably 3-4 of them sitting in my desk, unused, because these are so rarely needed.
And if you don't have one, they can be bought for a buck or two, delivered.

Exactly. Also answer to original question is: most likely impossible, because most DVI-DVI cables are not DVI-I but DVI-D "digital only" type, with some analog pins absent. More about DVI connector variations here: https://en.wikipedia.org/wiki/Digital_Visual_Interface
 
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Offline Mechatrommer

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #4 on: September 18, 2019, 03:28:23 pm »
bummer. all my DVI cables are DVI-D, no analog pins, so i have to buy the adapter anyway. and then checking DVI-D to HDMI converter, it seems there's hope...
https://sites.google.com/site/scidiy/pc-diy/hdmi-to-dvi-d

so i stripped both of them they indeed quite similar, 4 twisted pairs of differential signals with shield wire each, now i know what are those pins are, before i just a lame user. just still not sure what characteristic impedance are they? yes looks like this is going to be artful soldering technique to maintain integrity, minimize discontinuity, so tonight i'm going to rest first for a long day tomorrow.

That looks legit but the question is to why bother with this?
thanks for confirmation but it cant be done as stated above. why? because i need this the quickest i can without waiting idle during shipping, waiting idle can drive me nuts. but looks like i have to make the order and in the mean time try the DVI-HDMI diy. sad i cant setup my workstation soonest yet.

These adapters come packed with every graphic card, motherboard and what not these days (VGA outputs are getting rare, most cards have one or two DVIs and then only HDMI/DisplayPort connectors). I have probably 3-4 of them sitting in my desk, unused, because these are so rarely needed.
not in my case. this workstation (HP Z800) is aged came all the way from the USA, so its not come with any adapter (NVidia Quadro 4000 inside). even when i bought new graphics card many years ago, they didnt come with any adapter, just the cable. thats why i have few DVI cables right now. last time one of them is used on my older monitor, the rest are still unused. but nowadays, cheap monitor option only have VGA input, with HDMI if we are lucky. the one with DVI input i guess is the higher end one the more expensive price. i am now back to 27" vga monitor, cheapest in town. i cant justify DVI, they just look the same to me.

And if you don't have one, they can be bought for a buck or two, delivered. Also most stores selling computers will have adapters like this.
the nearest computer shop with enough and acceptable stocks is 100+ km away from me, so its not that easy.

Building this yourself can be a pain because if you aren't careful with shielding and soldering you are going to have signal integrity issues - noise, ghosting due to reflections, messed up colors, etc. Can be done, though.
many years back i managed to make usb extension cable about 5m+ long from thick wires used for electrical appliances to mains plug (3 prong) and then i add the fourth wire stripped from another cable, to connect to usb mobile internet donggle far away from PC to get better reception, it worked. its amazing to think back how i can do such thing on signal integrity tight line. i never heard words such as signal integrity nor differential signalling during that time :palm: i think this DVI-HDMI attempt will be a good lesson how we can stretch the limit, just now i read a discussion in another forum, they guy wrote we cant do this diy since "the HDMI cable is terminated in the factory (using machine)", so i will see how valid is this statement, so i can tell the story. cheers.


I have probably 3-4 of them sitting in my desk, unused, because these are so rarely needed.
And if you don't have one, they can be bought for a buck or two, delivered.

Exactly. Also answer to original question is: most likely impossible, because most DVI-DVI cables are not DVI-I but DVI-D "digital only" type, with some analog pins absent. More about DVI connector variations here: https://en.wikipedia.org/wiki/Digital_Visual_Interface
spot on as i just realized.
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Offline Mechatrommer

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #5 on: September 19, 2019, 07:25:39 am »
i found an online seller in our country selling all sort of adapters.

DP->HDMI
DP->VGA
DVI->HDMI
DVI->VGA
HDMI->VGA
VGA->HDMI

i'm ordering all of them since they are all cheap, about $20 incl shipping 10 qty all (some adapter i buy 2qty). so i can be the video adapters collector and hopefully will not have trouble again with some weird graphics card. lets see how i can fully utilize that NVidia Quadro 4000 ports (2 x DP, 1 x DVI-I), DP -> VGA and VGA -> HDMI adapters look suspiciously cheap since they should be active adapter type, but i'm ordering them anyway to see if they are for real, about $4 each, wont hurt much if they turn out to be fake or non working. in the mean time, while waiting for the shipping in this few days, tonight i'm going to connect the already cutted DVI-D and HDMI cables, just to keep me busy and to see how it goes signal integrity wise.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline janoc

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #6 on: September 19, 2019, 01:30:49 pm »
Be careful with those DP->VGA or HDMI->VGA adapters.

These invariably abuse the 5V line of the HDMI plug intended for powering up the EDID EEPROM in the monitor for supplying power to the video conversion chip. Some of these cheap adapters try to draw a lot of current from that line (more than the 50mA max that the HDMI spec describes) and could easily fry the voltage regulator on the GPU.

Better ones have a connector for external power.
 
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Offline tooki

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #7 on: September 19, 2019, 08:47:35 pm »
DP->VGA is something expressly envisioned in the DP standard, so that’s not “abusing” anything.
 
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Offline janoc

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #8 on: September 20, 2019, 03:16:02 pm »
DP->VGA is something expressly envisioned in the DP standard, so that’s not “abusing” anything.

You have missed my point. It is not whether a certain conversion is possible/envisioned but that some dongles that do this are poorly designed. I have two - one which draws too much current and did not work with a Raspberry Pi or my TV set-top box for that reason until I have hacked in external USB power. The other one has no issues.

DP's DP_PWR pin is supposed to supply up to 500mA (but only at 3.3V) which is 10x more than the 5V line of the HDMI. But even there a poorly designed dongle (and an underpowered DP port somewhere on a laptop) could cause issues.
 

Offline tooki

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #9 on: September 20, 2019, 04:07:18 pm »
DP->VGA is something expressly envisioned in the DP standard, so that’s not “abusing” anything.

You have missed my point. It is not whether a certain conversion is possible/envisioned but that some dongles that do this are poorly designed. I have two - one which draws too much current and did not work with a Raspberry Pi or my TV set-top box for that reason until I have hacked in external USB power. The other one has no issues.
So... uh... not "invariably" then?

But moreover, Raspberry Pi and STBs use HDMI, not DisplayPort, and thus are not what I was addressing.

DP's DP_PWR pin is supposed to supply up to 500mA (but only at 3.3V) which is 10x more than the 5V line of the HDMI. But even there a poorly designed dongle (and an underpowered DP port somewhere on a laptop) could cause issues.
I didn't say anything about the HDMI dongles. But DP->VGA is not a hack, and does not constitute "abuse" of the port. And I'm skeptical of claims of there being "underpowered" ports and dongles that violate the standard. (Making such an adapter is not trivial, so it's almost certainly just going to be one of a handful of COTS ASICs with the required support components.)
 

Offline Mechatrommer

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #10 on: September 22, 2019, 04:30:44 pm »
bummer. all my DVI cables are DVI-D, no analog pins, so i have to buy the adapter anyway. and then checking DVI-D to HDMI converter, it seems there's hope...
https://sites.google.com/site/scidiy/pc-diy/hdmi-to-dvi-d
i've assembled my diy dvi to hdmi cable, this is the best i can do (pictures), the hdmi cable i used seems like the cheapo one since data shields and any grounds are connected to one single wire (chassis), so i have to connect all DVI shields into one and connect to there. but it seems to work, i managed to setup my Z800, but i have problem with quadro 4000 driver in Win7Pro 32 bit, so i can only test 800 x 600 resolution meh. i dont think its likely the driver installation problem has to do with my diy conversion right?

next is i have to order writeable DVD greater than 5GB to burn Win7Pro 64bit ISO in it and try 64 bit installation, i hope quadro 4000 is ok there. i only have 4.7GB DVDRW which 64bit ISO installation cannot fit bummer. my plethora of adapters ordered earlier is 1-2 days away now.
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Offline Monkeh

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #11 on: September 22, 2019, 04:34:18 pm »
but i have problem with quadro 4000 driver in Win7Pro 32 bit, so i can only test 800 x 600 resolution meh. i dont think its likely the driver installation problem has to do with my diy conversion right?

It's likely you screwed up the DDC wiring.
 

Offline Mechatrommer

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #12 on: September 22, 2019, 04:38:54 pm »
but i have problem with quadro 4000 driver in Win7Pro 32 bit, so i can only test 800 x 600 resolution meh. i dont think its likely the driver installation problem has to do with my diy conversion right?
It's likely you screwed up the DDC wiring.
i checked and rechecked for continuity and short, everything seems fine, i'll check back again if its really matters. how can DDC problem will make 4000 driver crashed in Win7? earlier version gave me BSOD, later version gave me abysimal 4 bit color, but Windows default driver seems producing better color as you can see in the last picture above.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Monkeh

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #13 on: September 22, 2019, 05:01:00 pm »
but i have problem with quadro 4000 driver in Win7Pro 32 bit, so i can only test 800 x 600 resolution meh. i dont think its likely the driver installation problem has to do with my diy conversion right?
It's likely you screwed up the DDC wiring.
i checked and rechecked for continuity and short, everything seems fine, i'll check back again if its really matters. how can DDC problem will make 4000 driver crashed in Win7? earlier version gave me BSOD, later version gave me abysimal 4 bit color, but Windows default driver seems producing better color as you can see in the last picture above.

You didn't say it was crashing, you just said you couldn't get a proper resolution out of it..
 

Offline Mechatrommer

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Re: Home Made DVI-I to VGA Converter Possible?
« Reply #14 on: September 22, 2019, 06:28:48 pm »
well the driver installation is not so straight forward, i disabled 4000 driver in windows, reinstall ver 341.44, and it reported 3d vision driver or something that was installed earlier is not compatible, it removed it and now the quadro 4000 display is working yay. there some sort of ghosting, thin horizontal brighter line projecting from each windows edge (i cant get it in camera) but for me its not so serious. i'm not sure if its the cable's signal integrity traits, or my aging samsung tv monitor. but as always, "TV" monitor sucks at reading text anyway, this time is only to setup the Z800 while waiting for proper adapter for proper VGA "PC" monitor connection. so this diy is possible (i dont say its ideal), even on a budget cable. no need factory termination :P
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 


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