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'[EE] Cheapest way to drive 4 SVGA monitors'
2008\01\04@101126 by M. Adam Davis

face picon face
I'm considering a project which involves displaying essentially static
content on 4 15" LCDs.  Essentially static being defined as "If it can
be done cheaper at the expense of update rate, then let's make it
cheaper."  I'm thinking updating maybe once per minute.

I'd like to keep the hardware as cheap as possible.  I don't need to
do anything fancy, but one thing I do want to avoid is seeing the
screen slowly update - even though it's only updating once a minute or
so, I want the update to happen instantly.  The data for a new image
could come over USB, or a memory card, or whatever's convenient.  I
can always create a data path later, the thing I'm working on now is
the actual driving of four displays.

So the best I've come up with is using a cheap FPGA and some
reasonably fast SDRAM with enough space to hold two images - one
buffer, and one active.  This would be around 18MB for 4 displays of
1024x768x24bit imagery.  Unfortunately this runs to 540Mbytes/second
of memory throughput not counting updating the memory (1024x768 pixels
* 3bytes * 4 screens).

And from there the cost just goes up since I can't easily use an off
the shelf fpga board for this since the memory requirements are so
interesting.  I could get 4 separate FPGA boards, though.  I suppose a
high end FPGA board with DDR ram would do it, but cost is high.

I'd prefer not having 4 PCs running, but have considered getting a
cheap computer with several VGA adaptors and windows XP.  Would be
nice if it were smaller with lower power requirements though.  Might
be the cheapest option, and certainly the easiest/quickest to develop
for.

So...  Suggestions?  Any FPGA boards I should look at?  Alternative methods?

-Adam

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Moving in southeast Michigan? Buy my house: http://ubasics.com/house/

Interested in electronics? Check out the projects at http://ubasics.com

Building your own house? Check out http://ubasics.com/home/

2008\01\04@104748 by Herbert Graf

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face

On Fri, 2008-01-04 at 10:08 -0500, M. Adam Davis wrote:
> I'd prefer not having 4 PCs running, but have considered getting a
> cheap computer with several VGA adaptors and windows XP.  Would be
> nice if it were smaller with lower power requirements though.  Might
> be the cheapest option, and certainly the easiest/quickest to develop
> for.
>
> So...  Suggestions?  Any FPGA boards I should look at?  Alternative methods?

I would certainly be interested in the FPGA solution, it would be lowest
power by far, but if you're not going to make your own board, the PC
idea will be much cheaper.

Two dual head video cards are all you need, from that point it's just a
matter of software. I don't know what your budget is.

If low power is of upmost concern then an older laptop with some USB-VGA
adapters may fit the bill.

TTYL

2008\01\04@104856 by Picbits Sales

flavicon
face
Worth looking at the Parallax Propeller (I think) microprocessor - these
have VGA drive capabilities and run at silly speeds. They are also only
around $12 each but I have no experience of these at all other than spotting
another conversation about VGA driving on another forum and these were
mentioned.

Might be worth a look.
{Original Message removed}

2008\01\04@111008 by Mike Harrison

flavicon
face
On Fri, 4 Jan 2008 10:08:38 -0500, you wrote:

{Quote hidden}

Do a web search for 'digital signage'. There are some cheap media player type devices that will
display stuff from memory cards - the only question is whether you can get sufficient control.
They are likely to be cheap enough to use one per monitor.


2008\01\04@125222 by Vasile Surducan

face picon face
$350 ready made kit, using an FPGA
However a $20, 100MHz old desktop PC would be cheaper.
You didn't say if there is the same information on those four LCD or
it's different...

On 1/4/08, M. Adam Davis <spam_OUTstienmanTakeThisOuTspamgmail.com> wrote:
{Quote hidden}

> -

2008\01\04@131239 by Dario Greggio

face picon face
M. Adam Davis wrote:

> I'm considering a project which involves displaying essentially static
> content on 4 15" LCDs.  Essentially static being defined as "If it can
> be done cheaper at the expense of update rate, then let's make it
> cheaper."  I'm thinking updating maybe once per minute.

Welcome to the club :)
http://forum.microchip.com/tm.aspx?m=288313

Yeah, sure the FPGA way is the right one, but needs some development.

I'll be interested in how you proceed on that.

--
Ciao, Dario

2008\01\04@132744 by M. Adam Davis

face picon face
Is there a $350 ready made FPGA kit for this?  Or a $350 FPGA kit that
needs a few video dacs or R2R ladders or etc (minor stuff) to do this?

The displays need to be able to display separate info - otherwise a
$50 FPGA kit could do it with a video amplifier/splitter circuit.
However, they need to be synchronized (think video wall type app) so
separate controllers would need to be sync-able to some degree.  If I
could get a very cheap, very small, very low power solution that
couldn't synchronize better than within one second then I'd consider
it simply due to the other factors.  Shouldn't be too great an issue,
but does limit some choices.

I did poke around a bit.  Looks like an FPGA with 16 bit wide DDR2
200MHz memory (800MBytes/second) could manage the throughput.  Add
some video DACs...

-Adam

On 1/4/08, Vasile Surducan <.....piclist9KILLspamspam@spam@gmail.com> wrote:
{Quote hidden}

2008\01\04@134126 by M. Adam Davis

face picon face
There's a different approach - using PCI cards.  I always shied away
from them due to the bus complexity, but thinking back to my school
days I do recall going over it and thinking that it's not nearly as
complex as I had expected.  Still more than ISA...

Adds size, but may be simpler, and possibly cheaper if I can
creatively source some PCI cards...

-Adam

On 1/4/08, Dario Greggio <.....adpm.toKILLspamspam.....inwind.it> wrote:
{Quote hidden}

> -

2008\01\04@135826 by Marcel Duchamp

picon face
Is this a one-off, a fun hobby project, or a commercial venture?

If it's a one-off, here's something not quite the same but similar:

digital photo picture frame:
www.newegg.com/Product/Product.aspx?Item=N82E16882597005
brochure here:
http://www.viewsonic.com/pdf/us_eng/products/DF88W-523_Dec_2007a.pdf

USB connection and price around US$150...

M. Adam Davis wrote:
{Quote hidden}

2008\01\04@140504 by alan smith

picon face
So are you talking text or graphics?  Text..there is a company that has a serial to VGA interface (have it somewhere) and it works pretty good.  Just a TTL serial for commands to where you place the data (x/y offsets essentially) and then send the text to display.  You can update just pieces of it as well.
 
 If graphics....different story.  SVGA is what...1024 pixels x 768 lines, non-interlaced.  So your doing 8 bit graphics, thats 24 bits per pixel (RGB), times 1024 time 768. Thats just for one frame of what needs to be displayed.  Since you want a seemless update, you will need two video buffers.  Probably the easiest is to use VRAM (whoa...do they still make that?) or SDRAM, (i think it was SDRAM?) where you have a buffer that you dump a 'line' of data out and then you can serially stream it out.  Worked great on a video card I did years ago. So you have two sets of these, and you will have to constantly stream out one buffer else the video of course will just fade away.   The syncs are pretty easy, can just do a FPGA state machine for that....pre-sync, sync and post sync then the video for each line and then the vsync pulse including the blank lines for settle at the top.  Oh..this is all from driving CRT's but the LCD analog interface has to be the same.  For digiital
video, its a different story but its similiar. The video from each line if designed right, would be a stream of red, green and blue pixel data and that would then be driven directly into a triple 8 bit video DAC, and followed by a video driver.  The syncs can just be driven out using a line driver device.
 
 Updating the frame memory is simply setting the RGB values for each pixel.  Think of your memory as mapped to the display and it makes more sense as you address for this.  You didnt mention the 'source' for the data, so that will have to be considered.  Since you only need to update once a minute or so, that gives you plenty of time to stream in the new data.
 
 Sounds like a fun project. A challenge, but fun.

"M. Adam Davis" <EraseMEstienmanspam_OUTspamTakeThisOuTgmail.com> wrote:
 I'm considering a project which involves displaying essentially static
content on 4 15" LCDs. Essentially static being defined as "If it can
be done cheaper at the expense of update rate, then let's make it
cheaper." I'm thinking updating maybe once per minute.

I'd like to keep the hardware as cheap as possible. I don't need to
do anything fancy, but one thing I do want to avoid is seeing the
screen slowly update - even though it's only updating once a minute or
so, I want the update to happen instantly. The data for a new image
could come over USB, or a memory card, or whatever's convenient. I
can always create a data path later, the thing I'm working on now is
the actual driving of four displays.

So the best I've come up with is using a cheap FPGA and some
reasonably fast SDRAM with enough space to hold two images - one
buffer, and one active. This would be around 18MB for 4 displays of
1024x768x24bit imagery. Unfortunately this runs to 540Mbytes/second
of memory throughput not counting updating the memory (1024x768 pixels
* 3bytes * 4 screens).

And from there the cost just goes up since I can't easily use an off
the shelf fpga board for this since the memory requirements are so
interesting. I could get 4 separate FPGA boards, though. I suppose a
high end FPGA board with DDR ram would do it, but cost is high.

I'd prefer not having 4 PCs running, but have considered getting a
cheap computer with several VGA adaptors and windows XP. Would be
nice if it were smaller with lower power requirements though. Might
be the cheapest option, and certainly the easiest/quickest to develop
for.

So... Suggestions? Any FPGA boards I should look at? Alternative methods?

-Adam

--
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - - - - - -
Moving in southeast Michigan? Buy my house: http://ubasics.com/house/

Interested in electronics? Check out the projects at http://ubasics.com

Building your own house? Check out http://ubasics.com/home/

2008\01\04@141745 by Matthew Mucker

flavicon
face

So are you talking text or graphics?  Text..there is a company that has a
serial to VGA interface (have it somewhere) and it works pretty good.  Just
a TTL serial for commands to where you place the data (x/y offsets
essentially) and then send the text
to display.  You can update just pieces of it as well.
 


Check out the restaurant industry for these types of devices. They're used
to send order data from the POS terminal to the kitchen.  I'm sure you've
seen them behind the counter at your local McFastFood place.

2008\01\04@143240 by Vasile Surducan

face picon face
On 1/4/08, M. Adam Davis <stienmanspamspam_OUTgmail.com> wrote:
> Is there a $350 ready made FPGA kit for this?

Actually $400:

http://www.altera.com/products/devkits/altera/kit-cyc3-embedded.html



Or a $350 FPGA kit that
{Quote hidden}

>

2008\01\04@143307 by Vasile Surducan

face picon face
On 1/4/08, M. Adam Davis <RemoveMEstienmanTakeThisOuTspamgmail.com> wrote:
> Is there a $350 ready made FPGA kit for this?

Actually $400:

http://www.altera.com/products/devkits/altera/kit-cyc3-embedded.html



Or a $350 FPGA kit that
{Quote hidden}

>

2008\01\04@154924 by peter green

flavicon
face

> I'd prefer not having 4 PCs running, but have considered getting a
> cheap computer with several VGA adaptors and windows XP.  Would be
> nice if it were smaller with lower power requirements though.
How about using say a VIA epia based system? stick in a dualhead PCI
graphics card and then use a USB adaptor or something for the fourth
monitor.


2008\01\04@165714 by alan smith

picon face
you want it simple....is cost an issue then? Within reason ?

peter green <RemoveMEplugwashspamTakeThisOuTp10link.net> wrote:  
> I'd prefer not having 4 PCs running, but have considered getting a
> cheap computer with several VGA adaptors and windows XP. Would be
> nice if it were smaller with lower power requirements though.
How about using say a VIA epia based system? stick in a dualhead PCI
graphics card and then use a USB adaptor or something for the fourth
monitor.


2008\01\04@183229 by M. Adam Davis

face picon face
Well I want it all, but cost is the driving factor.  If I can't afford
it, I'm not going to do it.  If I can afford it, but it's large,
noisy, and power hungry I probably will.  Complexity is an issue in
that I don't want to spend any time doing maintenance, and I want to
spend as little time as possible building it unless it yields benefits
in either a marketable product, or tangible learning opportunities.

If possible I'd like to come out on the other end with a marketable
product, which means that the unit needs to cost less than ~$50 [USD]
in parts and labor (which I believe is possible given my current
optimism) for a memory card or USB version (monitors not included).

So while I'm looking at a lot of options, I'm focusing on building one
for personal use, and building a prototype using dev boards for proof
of concept as a product.  So the PC idea is fine, but it pretty much
throws out possible production.  Same with using the PCI cards.

-Adam

On Jan 4, 2008 4:56 PM, alan smith <micro_eng2EraseMEspam.....yahoo.com> wrote:
{Quote hidden}

> -

2008\01\04@195738 by Xiaofan Chen

face picon face
On Jan 5, 2008 4:48 AM, peter green <RemoveMEplugwashEraseMEspamEraseMEp10link.net> wrote:
>
> > I'd prefer not having 4 PCs running, but have considered getting a
> > cheap computer with several VGA adaptors and windows XP.  Would be
> > nice if it were smaller with lower power requirements though.
> How about using say a VIA epia based system? stick in a dualhead PCI
> graphics card and then use a USB adaptor or something for the fourth
> monitor.
>

I think this is a good solution. Use a cheap Via based system and two
dual USB to VGA adapter.

Something like this or roll you own to reduce the cost.
http://shopper.cnet.com/graphics-cards/startech-com-usb-2/4014-8902_9-31995595.html

Xiaofan

2008\01\04@200955 by William \Chops\ Westfield

face picon face

On Jan 4, 2008, at 3:32 PM, M. Adam Davis wrote:

> cost is the driving factor.

You're not going to get cheaper than an old PC and a
couple of commodity PCI video cards.  For production
you might have to worry about the pending unavailability
of PCI video cards, but it's likely you'd be able to get
pci-express "old PCs" in the same timeframe.

USB displays are another idea, but I doubt you'll hit
the $20/head price that cards make easy...

BillW

2008\01\05@014835 by Vasile Surducan

face picon face
On 1/4/08, M. Adam Davis <RemoveMEstienmanspam_OUTspamKILLspamgmail.com> wrote:
> Well I want it all, but cost is the driving factor.  If I can't afford
> it, I'm not going to do it.  If I can afford it, but it's large,
> noisy, and power hungry I probably will.  Complexity is an issue in
> that I don't want to spend any time doing maintenance, and I want to
> spend as little time as possible building it unless it yields benefits
> in either a marketable product, or tangible learning opportunities.
>
> If possible I'd like to come out on the other end with a marketable
> product, which means that the unit needs to cost less than ~$50 [USD]
> in parts and labor

I believed you are an old boy. It seems not.
:)


(which I believe is possible given my current
{Quote hidden}

2008\01\05@102650 by Dave Lagzdin

picon face
On 04/01/2008, M. Adam Davis <RemoveMEstienmanKILLspamspamgmail.com> wrote:
>
> I'm considering a project which involves displaying essentially static
> content on 4 15" LCDs.  Essentially static being defined as "If it can
> be done cheaper at the expense of update rate, then let's make it
> cheaper."  I'm thinking updating maybe once per minute.
>
> I
> So...  Suggestions?  Any FPGA boards I should look at?  Alternative
> methods?
>
> -Adam
>
> -

What about the "Propeller" ? They claim it does multiple video feeds

2008\01\05@202322 by M. Adam Davis

face picon face
I have one that I haven't played with yet - got to meet Chip at last
spring's ESC.

It's fast enough to drive several VGA monitors, as well as do color
composite video, but the internal memory is small so I would have to
look at using external memory.  Still, it would probably work well,
and should be fairly inexpensive.

Digikey has 4Mx16 (64Mbit) 133MHz SDRAM in TSOP for $2.66 in
quantities of one.  I could use one for each monitor to meet bandwidth
requirements if I'm happy with 16 bits of color.  They are fast enough
to give me 32 bits per pixel or drive two monitors as well (each
monitor needs 47M+ pixels per second).  They are 3.3V devices, and
standard SDRAM, so I imagine the propeller can handle them, though I'd
probably want to look at having a shared data bus so the pixel data
goes from memory to the DACs, rather than through the propeller.

Although I just unearthed another PC and a 2 output PCI card, so I
might just go the easy route...

-Adam

On Jan 5, 2008 10:26 AM, Dave Lagzdin <dtekk.comSTOPspamspamspam_OUTgmail.com> wrote:
{Quote hidden}

2008\01\08@044148 by Peter Bindels

picon face
Hey,

Do your monitors have a digital or analog input?

If analog, prepare to get a proper A/D converter. I've used the
onboard on an Altera DE1 kit (R-2R network) and it's too slow to drive
the horizontal speed of 640*480 at 60hz.

Driving 4 times 1024*768 at 60 hz would eat up about 750MB/s of
bandwidth in your memory. You would be best off with a 32-bit or
64-bit interface, fighting for the last few Hz is not fun. Using an
FPGA you would be able to get very far. DVI driving should be well
possible without any converter but with a bit more onboard logic.

You wouldn't need a big FPGA to do the driving, I think an 8k unit
from Altera or an equivalent one from another company (Xilinx, Actel,
Lattice etc.) would be sufficient in terms of connections. For
development, a DE1 like the one I have, or even a simpler board would
be sufficient, but do watch out that you get one with a 32/64 bit
memory interface (DE1 is 2x 16bit and slightly insufficient memory).

If it's just for you, make it with an old PC and four identical PCI
video cards. If it's not just for you, try the FPGA route for a lot of
learning.

Regards,
Peter

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