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 Getting a small VGA screen 
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Joined: Fri Aug 20, 2010 8:38 am
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Post Getting a small VGA screen
Hi everyone!

I'm making a portable game device for uni. The approach I've chosen is to use an FPGA to store images for the objects in the game, background and so forth. The FPGA basicly does all the drawing for the VGA screen. I'm also using a microcontroller as the "brain". It should calculate new positions for the objects and send it to the FPGA.

My question is, is there a small enough VGA screen avalable to fit in a small casing, say 2.5 or 3 inch? I have found some that runs on 12 volts, but that would mean a bit to many batteries. Also I have found some LCD modlues, but im not sure if they really work like a VGA screen (even though it uses Hsync and Vsync) This is one I have been looking at: http://www.crystalfontz.com/product/CFAF320240F-T

Alsow, I'm having some problems interpreting the data sheet for a development board. The parallax microcontroller has a 5 volt output, but it looks like the Xilinx FPGAs can't handle anymore than 3.3 Volts (or so it seems). IS there anyway around this? Or can you safely use 5v and current limiting resistors on this developent board: http://www.digilentinc.com/Products/Det ... d=S3EBOARD

Thank you for your time.

Q-bert


Thu Mar 10, 2011 1:37 pm
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Post Re: Getting a small VGA screen
q-bert wrote:
My question is, is there a small enough VGA screen avalable to fit in a small casing, say 2.5 or 3 inch? I have found some that runs on 12 volts, but that would mean a bit to many batteries. Also I have found some LCD modlues, but im not sure if they really work like a VGA screen (even though it uses Hsync and Vsync) This is one I have been looking at: http://www.crystalfontz.com/product/CFAF320240F-T


A lot of people seem to use those CrystalFontz screens.

They should have a built in graphics controller that will be easier to deal with than generating a VGA Signal. You should IIRC just have to interface with the graphics controller on the LCD and send you data to the right registers and the video memory. If you want something for games, make sure it has a bitmapped mode. Some just have like all Tile based modes for like text. That would be fine for a tile based game though. XD

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Thu Mar 10, 2011 3:25 pm
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Post Re: Getting a small VGA screen
Better and cheaper - newhaven.com

Andre'


Thu Mar 10, 2011 9:21 pm
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Post Re: Getting a small VGA screen
Do I need to know the password or something? XD The secret knock? Because all I get is a blank page.

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Thu Mar 10, 2011 9:47 pm
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Post Re: Getting a small VGA screen
http://www.newhavendisplay.com/

Andre'


Fri Mar 11, 2011 3:32 am
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Post Re: Getting a small VGA screen
Wow, nice site Andre' they have some really nice LCDs for cheap. Those COGs are really inexpensive.

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Mao Mao Games


Fri Mar 11, 2011 3:58 pm
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Post Re: Getting a small VGA screen
Thanks guys!

I ordered a 3.5 inch screen with touch and a thingy to put in a breadboard. When I get it up and running ill post some pics :)

Any ide about the Spartan board? Is there a way to get around the 3.3 Volt input?

Q-bert


Sun Mar 13, 2011 7:51 am
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Post Re: Getting a small VGA screen
What's the problem with 3.3V? What exactly are you doing?

Andre'


Sun Mar 13, 2011 9:37 pm
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Post Re: Getting a small VGA screen
I'm using the Parallax microcontroller, which has 5 Volt output, to controll an Xiling FPGA, which apparantly has a maximum input voltage of 3.3 Volt. If I directly connect the two, I'm guessing the FPGA blows up..?

Q-bert


Mon Mar 14, 2011 3:11 am
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Post Re: Getting a small VGA screen
Propeller uses 3.3V not 5V. So, if you are running the Prop at 5, it WILL malfunction. Run it at 3.3V. That said, FPGAs have 5V tolerant inputs (or should depending on the product). And if you wanted to put a 5V signal into a 3.3V FPGA input, just put a 100 ohm, or you can put a voltage divider or you can put a level shifter. But, a 100 ohm resistor usually is enough. But, you can read up on 5V and mixed voltage processing for the FPGA and see what they say as well, usually they have the feature built in.

Andre'


Mon Mar 14, 2011 10:44 pm
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Post Re: Getting a small VGA screen
I'm using the XGameStation Pico Edition Kit 1.0, which I'm pretty sure uses a 5Volt regulator and has 5 Volt outputs?
Anyway, I'll just stick 100 Ohm resistors between the FPGA and microcontroller, and hope for the best.

Thanks Andre!

Q-bert


Tue Mar 15, 2011 1:33 am
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Post Re: Getting a small VGA screen
Read your sentence in the post above:

"I'm using the Parallax microcontroller, which has 5 Volt output, to controll an Xiling FPGA, which apparantly has a maximum input voltage of 3.3 Volt. If I directly connect the two, I'm guessing the FPGA blows up..? "

The only microcontroller Parallax makes is the Propeller. But, you are referring to their SX processor designed by ubicom and sold by Parallax, the SX28.

You see when I read that, it sounds like you are talking about the current parallax micontroller the Propeller chip. Not something from 10 years ago, the SX28 on the Pico which parallax didn't design.

Anyway, yes, 100 ohm should be fine to limit the current into the FPGA, but like I said, read the FPGA manual and I am almost certain you can set the inputs to be 5V tolerant, if not then resistors will work fine for now. But, in a consumer design you want level shifters or voltage dividers. Also, you should be able to set the IOs of the FPGA to 5V in most cases, they run off a different supply called VCCIO, the core runs at VCCORE, etc.

Andre'


Tue Mar 15, 2011 5:23 am
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