View Full Version : Highest resolution possible with HYDRA

02-08-2007, 08:33 AM
I am a newbie to the chip and to this forum. But I've done fair amount of embedded programming with LPC2138 chip and now considering Propeller chip for a graphics app where text and some graphics need to be overlayed over video signal (OSD). A question to experts: what's the highest resolution possible with the chip. I.e. if RAM size is not a problem, is it possible to drive XGA (800x600) display with it? What about 600 horizontal pixels in NTSC?

Mike Green
02-08-2007, 09:58 AM
There have been text drivers posted that can produce 1600 x 1200 pixels. I believe they tie up 6 of the 8 cogs in doing so. There's not enough memory for a bitmap that large, so no graphics drivers have been tried at that resolution. Chip posted a tiled driver with a 1024 x 768 pixel resolution that can handle mixed text and graphics, takes only 2 cogs for the VGA and a separate cog if you want an overlaid cursor.

NTSC is a different matter. The limitations there are in the video format. You can't realistically get 600 horizontal pixels and only 225-240 vertical lines.

02-08-2007, 09:39 PM
1600x1200 - wow! That's 115 Mhz pixel rate, assuming 60 Hz refresh. Does it mean that Propeller·can draw·to the screen faster than the CPU clock? It's impressive even if it takes all the cogs to do it.

02-08-2007, 10:24 PM
· There is some NTSC OSD code I wrote in the Propeller object exchange.
· http://ww1.parallax.com/Default.aspx?tabid=65
· It's the very last one "Video Overlay 256x192 pixels"


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Mike Green
02-08-2007, 10:24 PM
Chip figured out how to synchronize several cogs. Here's the thread: http://forums.parallax.com/showthread.php?p=617313.

02-09-2007, 01:32 AM
Thanks guys!

Looks like I am ready to do the plunge.

The overlay project is exactly what I am looking for, but may be with higher resolution. I only want to·overlay borders of the screen,·~20% of total·area,·so there should be enough RAM to support it. I am sure will have more questions later. But for now I just order the board and read up the docs.

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Post Edited (cyber-flyer) : 2/8/2007 6:36:48 PM GMT

02-09-2007, 07:12 AM
Also, if you did buy a hydra the book and cd that comes with it have multi-cog NTSC drivers that use up to 8 cogs if you want. They more or less drive the display to 256x192ish, BUT they support sprites and other features needed to do high end graphics. Thus, even without bitmap memory, you can, with our drivers create highly detailed graphics on the screen with objects moving on top of each other without the need for a bitmapped display.


02-09-2007, 08:17 AM
Thanks, yes I am getting the HYDRA book as well.