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[SOLVED] Frame rate of a screen

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bilal_oct

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I have generated VGA signal, both data and timing (RGB and v_sync, h_sync) at the rate 60 Hz from FPGA. The frame size consist of 640 x 480 pixel. I have tested the signals v_sync, h_sync by connecting them to LEDs on board, which works fine but there is no output on the screen just screen turns black.

I am not sure about the frame rate of DELL screen. How to detect the frame rate of a screen ? I guess I need to synchronize the VGA signal from FPGA with according to the screen. Any idea how to do this ?
 

black screen = accepts sync but read no data at RGB pins !
 

There are a great many standards for "VGA" and software will try to interpret the incoming vertical and horizontal syncs to determine which member of the VGA family it is.

If what you have produced falls outside one of the recognised standards, the monitor will either stay blank, or come up with an on screen error message.

There is a website:
http://tinyvga.com/vga-timing
This has all the standards listed.

I built myself a successful hardware VGA generator, the standard I used is the VESTA standard 1280 x 1024.
I used a 10.24 Mhz crystal divided by 160 for the 64Khz line rate, and the line rate was divided by a further 1066 for the 60.04 Hz field rate.

There are many other alternatives to that.
 
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Very helpful info, Tony.
I've struggled with SXGA display, I wish I had had this info before!
 

I tried feeding a vesta to my monitor but it blew a fuse.
It seems it prefers chow mein to curry...:smile:
 

Any of the standards listed should work, but some require strange crystal frequencies, or some very odd division ratios.

What seems to be most important are the frequencies. Sync pulse widths do not seem that critical, and the blanking intervals make up the active part of the display need to be fairly close.

You can fudge the blanking, and use the display height and width adjustments plus centring to avoid cropping or black edges.
But if you wish to have it display a perfect picture without tweaking, using the default monitor settings, stay as close as you can to the spec blanking intervals.

It can be a very frustrating business to get something up on the screen initially.

One other point, the video must be absolutely clean without any noise or ringing on the grounds, otherwise a plain background will look awful. Even a few millivolts of nose will be clearly visible.
Circuit board layout and a clean ground reference around the video output drivers is absolutely critical to getting clean video.

Its all jolly good fun, and a particularly interesting challenge.
 

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