True 640x480@60Hz

EB

I am attempting to drive a VGA LCD display (a·Datalux 8794-01/7D-18005)·with a propeller chip, and running into some trouble. The display in question works only at 640x480@60Hz. I have verified that the display works by connecting it to a computer. I know the propeller video generator works, because it runs all of the video generator demos without any problems (when connected to a more flexible monitor, of course).

Modifying the VGA_text (which runs at [url=mailto:512x480@60Hz]512x480@60Hz[/url]) code sample, I tried:

• h front porch =·16
• h synch pulse = 96
• h back porch = 48
• v front porch = 10
• v synch pulse = 2
• v back porch = 33

These settings did not work. I'm looking for the settings to run the VGA.spin driver at a true [url=mailto:640x480@60Hz]640x480@60Hz[/url], or some documentation on how the VGA.spin driver uses the various values and what exactly they mean so that I can work out what I need on my own.

Thanks!

Paul Baker

Hi EB, I don't have the VGA specs for you, but there are some people that have worked with 640x480 drivers:


http://forums.parallax.com/showthread.php?p=725697

http://forums.parallax.com/showthread.php?p=630051

http://forums.parallax.com/showthread.php?p=735992

http://forums.parallax.com/showthread.php?p=658972

and there is this object in the object exchange: http://obex.parallax.com/objects/86/

I don't know if any of the efforts specifically come out to a 60Hz refresh rate, but you should be able to swap out the crystal with one which will drive the screen @ 60Hz (calculate the fps generated, and new crystal value should be = (60Hz/Measured frame rate)*5MHz, it may require using a programmable oscillator if the necessary frequency is a non-standard value.

VGA.spin has a commented section at the end of the file that explains the parameters.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.