VGA Port on zedboard

Hi,

I am trying to stream a series of 256 level grey scale images through VGA port of zedboard. Usually I copy the same grey level data onto 3 RGB channels to get grey scale image. The problem is that each R,G and B channel coming out of PL are 4 bits wide and I am confused on how to represent my 8 bit greyscale on 4 bit values. Should I decrease my intensity levels to 16 and write the same values on each og the R,G and B lines coing out of PL.

Any suggestions would really help.

Thanks,
Harsha

0 zedhed over 10 years ago

Hello Harsha,

I found some further information on this type of VGA connector on the Digilent site. There is some further explanation here in the VGA section of the Basys3 page:

https://reference.digilentinc.com/basys3:refmanual#vga_port

You are correct that the color depth for the VGA connector is 4-bits deep which would allow for a total of 2^12=4096 colors to be displayed. As you pointed out for grayscale the R, G, and B values would need to be the same which allows for only 2^4=16 combinations. So you would need to find some way to scale the 256 levels down to only 16 levels, which could probably be done by truncating you video data by dropping the lower 4 bits of your 8-bit grayscale data.

My recommendation for better video performance and color palette would be to switch over to the ADV7511 HDMI chip that is on your ZedBoard. There are reference designs which show how to use this such as the "HDMI Bare Metal Reference Design Using ADV7511 and ADI IP" tutorial on the reference design page here:

http://zedboard.org/support/design/1521/11

Regards,

-Kevin
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0 Former Member over 10 years ago in reply to zedhed

Thanks, I could sort out my confusion
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0 Former Member over 10 years ago

Thanks,

I could sort out my confusion.

Harsha.
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