mrbrown
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Re: HDMI to VGA connector

Thu Sep 22, 2011 3:33 pm

So I have been looking and I have seen an HDMI to VGA (female) adapter, Its cheap like $4, but they ask for like $15 in shipping. It weighs an ounce I cant see that unless it is next day. So at this point I am looking at a cheap HDMI cable to a HDMI to DVI then a DVI to VGA, so I can use one of the 6 monitors I have just sitting in my basement. Has anyone seen a connector out there that would be better then this chain of daisies?

I do not have a lot of cash to buy neato monitors and a TV is not an option since I am not looking to spend more then $50 total (RasPi, connector, monitor(free since I already have 6)) per piece of pi.

jtucker
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Re: HDMI to VGA connector

Thu Sep 22, 2011 4:14 pm

The cable won't work for this. HDMI is a digital signal and VGA is analog signal. You'll need a HDMI to VGA converter and they run from $70.00 to $100.00.

Thunder__X
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Re: HDMI to VGA connector

Thu Sep 22, 2011 5:02 pm

Quote from mrbrown on September 22, 2011, 16:33
So I have been looking and I have seen an HDMI to VGA (female) adapter, Its cheap like $4, but they ask for like $15 in shipping. It weighs an ounce I cant see that unless it is next day. So at this point I am looking at a cheap HDMI cable to a HDMI to DVI then a DVI to VGA, so I can use one of the 6 monitors I have just sitting in my basement. Has anyone seen a connector out there that would be better then this chain of daisies?

I do not have a lot of cash to buy neato monitors and a TV is not an option since I am not looking to spend more then $50 total (RasPi, connector, monitor(free since I already have 6)) per piece of pi.

It won't work because Hdmi and the newer dvi are digital formats and Vga is analog. You could try buying a upscaler to scale composite video to video, but honestly, upscaling a composite source to vga would look horrible. It's too bad there's no rgb scart output on the pi.

mrbrown
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Re: HDMI to VGA connector

Thu Sep 22, 2011 8:23 pm

Oh see I just figured it would work since I have used a DVI to VGA connector for my monitors before I got a DVI compatible monitor.

Thank you, probably just saved me some frustration wondering why it wasn't working!

obarthelemy
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Re: HDMI to VGA connector

Thu Sep 22, 2011 8:45 pm

To be encyclopedical on a subject that keeps popping up:
There are 2 possible types of signals, Analog, and Digital. And then there's connectors.
VGA is only analog.
DVI can be Analog (DVI-A), Digital (DVI-D) or both (DVI-I, "I" is for integrated). DVI-A is rare, -D frequent, and -I quite frequent too, though some there are nasty surprises for people who assume all DVIs are -I: they aren't !
HDMI is almost always Digital, though there is a provision for Analog output, which is almost never present. You can assume HDMI is always Digital-only, and it is Digital-only in the Pi.

Passive cables convert from one type of Analog connector to another are cheap ($5-$10): VGA to DVI-A; DVI-A or -I to VGA. You can also do the same from Digital to Digital for as cheap: HDMI to DVI-D, and DVI-D or DVI-I to HDMI.
But if you want to go from Analog to Digital (VGA to HDMI), or the other way (HDMI or DVI-D to VGA), you need an active cable/converter, and that's $50-$100.

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TonyD
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Re: HDMI to VGA connector

Fri Sep 23, 2011 10:44 am

@obarthelem-y, thanks for the comprehensive posting, its all makes sense to me now :)
Tony

trigger
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Re: HDMI to VGA connector

Mon Sep 26, 2011 11:52 am

So what's involved in making a HDMI to VGA adapter for the Raspi? Does anyone have any circuit designs to do this?

Jason
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Re: HDMI to VGA connector

Mon Sep 26, 2011 1:24 pm

Quote from trigger on September 26, 2011, 12:52
So what's involved in making a HDMI to VGA adapter for the Raspi? Does anyone have any circuit designs to do this?

I can't see this being easy (unless there are off-the-shelf IC's to do this)
HDMI is basically high speed digital data, whereas VGA is analog RGB with some timing information.
Any DIY system would be an ASIC or Fast FPGA.

There are existing products to do the conversion for about £50/$50, its not going to be a simple cable and so any £5 cables will not work.

If you simply want to via the 'Pi on a PC screen, then the options are limited;
-VNC/Other remote network access
-HDMI to VGA module
-Purchase a more flexible PC Monitor with HDMI or DVI (this *should* work and you can get cables to change connections..)

http://en.wikipedia.org/wiki/HDMI
(note: small royalty payment required for HDMI products..)

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abishur
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Re: HDMI to VGA connector

Mon Sep 26, 2011 1:31 pm

I've been looking into HDMI to LVDS for a laptop monitor hookup... long story short you're better off just buying a pre-made adapter. The chips required to do the translating, while not being expensive, are those little square chips with about 25 pins on each side (for a total of 100 pins) and you usually need to use two of those. One to take it from HDMI to a generic analog format, then another to take it from the generic analog to VGA (or LVDS in my case). Also getting thrown into the mix is a chip to convince the HDMI that it still has the HDCP handshake going on so it will continue to output video correctly. Unless you want to solder your wires to those tiny pins, you'll also need to etch or purchase a pre-etched circuit board.

But hey, if that sort of circuitry stuff is your cup of tea than a good google search will give you the best answer! Otherwise, I'd just purchase a pre-made board. :(
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trigger
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Re: HDMI to VGA connector

Mon Sep 26, 2011 1:48 pm

The soldering side is not really a problem for me (I'm a surface mount engineer) but I'd need the circuit design and the PCB layout. Just thought one of you serious boffins would have it hand. :)

Tide
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Re: HDMI to VGA connector

Mon Sep 26, 2011 2:51 pm

Well I guess this should give you some ideas. Better warm up that soldering iron!

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Michael
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Re: HDMI to VGA connector

Mon Sep 26, 2011 6:43 pm

Quote from Tide on September 26, 2011, 15:51
Well I guess this should give you some ideas. Better warm up that soldering iron!


Actually, that circuit diagram is not ideal - it basically requires a very unfussy VGA monitor to work.

For an idea of what is involved for HDMI to VGA, take a look at this page and the linked datasheet.

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abishur
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Re: HDMI to VGA connector

Mon Sep 26, 2011 7:31 pm

That's exactly the sort of complexity I was looking at! Which is also why I ultimately decided that when the time comes, I'm just going to buy a premade one.
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Lakes
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Re: HDMI to VGA connector

Mon Sep 26, 2011 11:45 pm

Would composite to VGA be any easier to do?
Not ideal I know, but maybe cheaper than having to use a HDMI to VGA.

obarthelemy
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Re: HDMI to VGA connector

Tue Sep 27, 2011 12:11 am

there's post somewhere in here to that effect indeed. Monochrome though, I think.

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abishur
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Re: HDMI to VGA connector

Tue Sep 27, 2011 1:48 am

possibly, but then wouldn't you be stuck with that *very* low resolution? If it makes any difference the r-pi team recognizes what a big need VGA is and I'm expecting that the second revision of the r-pi, will have a VGA port. So if the lack of VGA is a deal breaker, I'd either fork over the $40 for an HDMI adapter or wait for the next revision of the r-pi and hope that the VGA port makes the cut. :?
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Michael
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Re: HDMI to VGA connector

Tue Sep 27, 2011 7:15 am

Quote from abishur on September 27, 2011, 02:48
the r-pi team recognizes what a big need VGA is and I'm expecting that the second revision of the r-pi, will have a VGA port.

I really hope they do it as an add-on board for the first and second generation. Personally, I wouldn't want it to be on the main board because of the cost and board dimensions implications.

Lakes
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Re: HDMI to VGA connector

Tue Sep 27, 2011 10:40 am

+1 for VGA add-on board, people are giving older CRT/VGA monitors away, much better to reuse them then scrap them!

jg
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Re: HDMI to VGA connector

Sun Nov 13, 2011 10:33 pm

Quote from abishur on September 27, 2011, 02:48
possibly, but then wouldn't you be stuck with that *very* low resolution? If it makes any difference the r-pi team recognizes what a big need VGA is and I'm expecting that the second revision of the r-pi, will have a VGA port. So if the lack of VGA is a deal breaker, I'd either fork over the $40 for an HDMI adapter or wait for the next revision of the r-pi and hope that the VGA port makes the cut. :?

Is there any more info on this Rev-2 with VGA comment ?
Can the silicon support VGA (relatively) easily ?

radix
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Re: HDMI to VGA connector

Sun Nov 13, 2011 10:52 pm

just want to be sure... HDMI-DVI connector will be working right ?

kme
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Re: HDMI to VGA connector

Mon Nov 14, 2011 12:12 am

Can the silicon support VGA (relatively) easily ?Not at all. It will require a completely new subsystem to convert digital HDMI to analog VGA. The SoC has HDMI- and composite-out and that's it.

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abishur
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Re: HDMI to VGA connector

Mon Nov 14, 2011 4:07 am

@radix, yes hdmi->dvi is just a matter of pin movement so it's a passive cable and works just fine.

And as KME stated, the GPU doesn't support VGA at all. It does support HDMI and composite video, but not VGA. To get it to work would require a minimum of two extra chips, a lot of pcb realestate, and most likely an extra layer on the pcb. That adds up to a ton of money!

They have stated that they recognize that VGA is still very important and they're looking at possibilities to get it on some future revision, but for the time being, they're focusing their time and energy where it will be more productive (like getting the board actually released ;) )
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Drith
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Re: HDMI to VGA connector

Tue Nov 15, 2011 5:36 am

Would a RCA to VGA cable help?
http://networkcable-tester.com.....a-cable-5/

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abishur
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Re: HDMI to VGA connector

Tue Nov 15, 2011 6:58 am

Well, the item you linked actually goes from a VGA port to an RCA port (not the other way around), but even then it only works for a very small amount of VGA cards. See what is actually happening here is that a video card maker said "hey, this pin isn't used by VGA, let's send our composite video out there and save money!" So they did and ever since then we've all been tricked into thinking that a passive cable could convert VGA to RCA and vise versa :)

That said if you wanted to go from RCA to VGA you could buy a ~20 active adapter but that's an extra 20 bucks....
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Bikko
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Re: HDMI to VGA connector

Tue Nov 15, 2011 7:15 am

A little off topic but thread reminded me of this.

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