VGA Driver rate using GPIO

[alzomor]

Hi

I am devloping a LCD VGA driver using GPIO's
I need to ask is it possible to drive the LCD at lower refresh rate?
for example my LCD is 70Hz, can I drive it at 15 or 30 Hz?

Regards
Hossam Alzomor

 

[jiangfux]

Yes, you can.
I drive LCD at 25Hz, no problem.

But i think you drive LCD with GPIO is not possible. You can use FPGA or CPLD to drive LCD.

 

[alzomor]

Thanks Jiangfux,

If you are using 25Hz with 800*600 resolution the total number of pixels per second is 12MPixel and if the processor is running at 24Mhz we have two instructions per Pixel and if the processor is running at 24Mhz we have 4 instructions per Pixel.
am I right?

May you give me some information about your timing?

Regards
Hossam Alzomor

 

[jiangfux]

alzomor,
If LCD is run at 25Hz with 800 * 600 resolution, the total number of pixels per second is 12MPixel, but the clk of the LCD shoule more than 12MHz, because the blank at start of line and end of line, may be 18MHz.
If you use gpio to drive LCD, processor running at 24MHz, two instructions per pixel, but your program shoud do something else, E.X, fetch pixel data, do loop instructions, and so on.
As i mentioned before, you can use FPGA + SDRAM, or use CPU with LCD driver(BF531 with ppi).

 

[alzomor]

ThanksJiangfux,

I am thinking of 15 FPS
Here's a project that the Job using GPIO
https://www.artekit.eu/vga-output-using-a-36-pin-stm32/

May you kindly give me some information about the timing for driving the LCD at 25MHz as in your project.


Regards
Hossam Alzomor

 

[jiangfux]

May you kindly give me some information about the timing for driving the LCD at 25MHz as in your project.

Sorry for my poor english. I think you should get the timing for driving the LCD in datasheet. Timing of LCD is different from one to another.

- - - Updated - - -

Here is timing of my LCD.