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March 7th 2006 Open Graphics Project Newsletter

OGD Alternative Usages: the wild, the crazy and the interesting

  • An Open Graphics-card being able to detect (read out) the connection of the special Dutch Scart cable preventing an out of range signal unless the software or user claims the TV is capable (a very few nineties high end TVs were VGA 800x600 compatible).I

Progress, developments and discussions

GEDA Schematics

P. Sartain: For project information including contact details, aims and objectives, and links, please find the post "gEDA Schematics: Status 20060314" Symbols & scripts: http://www.kaear.co.uk/ogp/
As of March 14th 2006: Peter has kindly submitted a header-creation script called headergen. You can find it in the scripts directory. This script is GPL'd and copyright Sharp Laboratories of Europe Ltd. A second version of the ECP2_50 FPGA schematic has been added, with only one column of pins it more closely matches the symbols in the schematic. The schematics do not appear to include the ground connections listed in the ...ECP2_50... datasheets. The BGA claims to be a 672 pin, there are 771 pins listed in the datasheet.

Next step: Amend the signal list and rebuild the ECP2 fpga. Create the smaller LatticeXP and DRAM symbols and sanity check these against the schematics.

OGD1,Programming the LatticeECP2

T. Miller Our parts supplier assured us that this part is supported by the FREE tools. Piete posted this link: http://www.latticesemi.com/products/designsoftware/isplever/ispleverstarter.cfm Users queried about the need for repeated licenses to run the free tools. However it was pointed out by Timothy that the ECP2 is VERY new. IIRC, you can just get a new license every 6 months (this is to encourage you to upgrade), and the ECP2 will be supported by the time we need it. Regretably it currently requires windows to run. He then added: I'm sure this project will quickly spawn attempts to correct this problem, and they would be happy to have you assist them. J. Taylor downloaded and installed the package for Windows: "ispLEVER 5.1 Starter" on Linux with CrossOver 5. He reported that this appears to have installed properly, but I have problems that someone that has it on Windows could probably answer


J. Knutar: The standard cable used for connecting DVD players, came consoles, etc, in europe. TV sets sold have always scart and antenna connectors,the other connectors that are the de-facto standard in the US, don't appear on TV sets here nearly as often. http://en.wikipedia.org/wiki/SCART

Video Over Scan and OGP

L. Verhagen felt that: in 2006. Monitors can handle it. Other monitors have blown up already. J. Carol offered Burning out monitors with incorrect drive signals is no myth. I've got three high-end fixed-frequency monitors whose tech manuals warn against that in the strongest terms. Their sharpness is outstanding, but they can't tolerate mode-switching. They come from the days when there were no published standards, and every video board and monitor was custom. A workstation would run with exactly one graphics board, which was factory hardwired to exactly one mode, and it was sold with a monitor designed fromthe ground up for that mode and no other.Newer monitors are protected against excessively high sweep rates, because newer computers are a lot less predictable in the video modes they can generate.

T. Miller was not concerned: The solution is to have custom firmware that sets the mode and drivers that detect that it's a fixed-frequency firmware and respect that..

OGPD Design and Revision

OGD1 Hardware and Feature Clarifications

Selection of LatticeECP2 over Xilinx

H. Parker responded to a query about the selection of a Lattice chip. If your wondering why we chose a device that had some restrictions in the types of I/O it supports, get a low volume quote from your local Lattice rep and compare with Xilinx Spartan 3. I guarantee you'll be gobsmacked.

DAC Clock Rate

J Richard Taylor examined some issues about the video DACs: It seems that we have a very expensive solution for this so I was wondering about the required specs.
1. What is our max clock rate for the DACs?

T. Miller 330MHz for the one being populated.
2.What is the bandwidth required for the video out buffers.

Memory and buffers

J. Richard Taylor: I couldn't find a video SRAM in the design? I would want this as a feature in the final board and would prefer 12 bit per color. T. Miller: The video framebuffer is stored in graphics memory (Those DDR ram chips on there) and read out as we're scanning the display. And you're going to get 8 bits per color. Remember that OGA is somewhat of a minimalist design, targeted at performing well for desktops. Neato stuff like programmable shaders and higher RGB color depth is reserved for later generations, when we can afford it. I could possibly provide a drawing mode where green is 12 bits, reducing red and blue to 6 bits, but you won't get this for videooutput. A design decision was made very early on where pixels are fixed at 32-bit ARGB. Even 8-bit pseudocolor mode is just a trick of the host interface.

R. Jacquot felt that pinnable buffers (each windows needs an RGBA buffer - texture or something) so that it could be drawn on independently then each window is composited onto the main frame buffer would be good. T. Miller: Our rendering engine already has this as part of its design requirements. You can create buffers of arbitrary size, draw to them as though they were the screen, and then composite them as you like to other buffers, such as the main display.

The monitor input

It was suggested that this could be an error - should it be 75 ohm for R90, R100, & R110. A discussion ensued.

Analog Outputs
J. Richard Taylor: we have two analog outputs. Perhaps a block diagram added to the schematic would help. The video buffers are for the higher resolution head on page 13


It was felt that supporting LCD modules,should be left for OGD2, the next development board. T. Miller pointed out: we can rig some hacked OGD1 cards for specialpurposes. Since we want OGA to interface to things like notebookLCD's, we do want to do LVDS, but that won't require as extensive testing as things like the rendering engine. Most people don't have the hardware to test an LVDS interface, while we could buy a spare LVDS monitor off of Tech Source or something. J. Carrol Experience with OGD1 is likely to refine everyone's ideas of what additional features might be desirable in a development board, either for later phases of OGP or for outside customers. This is yet another reason to stay the course as presently planned, and not put more than minimal effort into feature creep during this release.


H. Parker I agree being able to to do LVDS would be really good. However, there are a number of restrictions that make this difficult. The Lattice device does support LVDS. However, it only supports LVDS outputs on banks 2,3,6 and 7. The Lattice device also has built in support for DDR interfaces, but only on banks 2,3,4,5,6 and 7. Most of the interfaces the card to memory and video ICs are either DDR or LVDS. The memories, DVI and TV-out are DDR. The high speed DAC is LVDS. All the banks that support DDR and LVDS are fully utililized supporting these interfaces.
The only remaining pins left after hooking up the memories, DVI, TV-out and High speed DAC are on banks 0 and 1. These pins only support LVDS inputs. However, there is a way to do pseudo-LVDS out with the use of external resistor networks. I will look into this in more detail when I have time.

Accelerated Vector Graphics

A post asked about accelerated vector graphics being added, but t. Miller cautioned:There's a bunch of development on OGD/OGA that needs to be done before we can get to the rendering engine. By that point, we may revisit some of our earlier design decisions. Be sure to bring this back up when we reopen that discussion.

Who is Who..

None new this week.

OGP in the News and on the Web

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Created by josephblack. Last Modification: Saturday 20 of June, 2009 14:22:03 UTC by josephblack.