Forum Discussion
Honored ContributorUP VGA Pixel Buffer problem
Hello,
I'm trying to use vga pixel buffer as a data source for the vga controller in SOPC builder on a DE2 board using Quartus 9.1. I'm not really sure what I need to use with the pixel buffer. After some reading on the altera vga note, I found that it needs the SRAM to store pixel data. I think the problem is the SRAM, I managed to output pixels to my monitor but its only garbage. Could someone enlight me on how to connect SRAM and pixel buffer in SOPC builder? Note: VGA controller, pixel buffer and SRAM components come from the University Program IP Core. I put a screen shot of my SOPC build in attachment.26 Replies
Altera_ForumI finally solved my problem!
Components connections are shown in my attachment. I set the pixel_buffer "Default Buffer Start Address" to the base address of the SRAM (0x00900000). Plus, I added the Alpha_blender so I can display both source at the same time on my monitor. char_buffer is displayed as foreground and pixel_buffer as background. pixel_buffer is configure to work in 320x240 (width factor: 2, height factor: 2) and color space is 16-bit RGB.- Altera_Forum
Have You changed anything in VGA Controller and Pixel Buffer design files? I am trying to make them working but I have only black screen...
- Altera_Forum
Hello ronix5000,
Have you look at my screenshot of my system build? Make sure vga_ctrl clock is set to 50MHz (other components connected to it will need to be at 50MHz too). Pixelbuffer needs SRAM to work. Pixels will actually be stored in this SRAM. Last thing, pixelbuffer needs its start address (in the properties) to be set to base address of SRAM. I have not made any changes to design files. If you want to test if vga controller is working, you can try to connect only the character buffer (without alpha_blending and SRAM). Hope this will help. Regards - Altera_Forum
I have DE2-70 board and I have been trying to generate 640*480 pixel vga signal but I have a message like "could not open pixel buffer device".
if there is anyone who design it using "video out university ıp core" and make it work,could you share sources codes (.SOPC,.V,.C,.SOF,.ELF .....). - Altera_Forum
What string are you passing to alt_up_pixel_buffer_open_dev() function and what is its device name located in system.h ?
- Altera_Forum
Hello renaudberube!
Thx for your reply! I found out what was wrong - I made some terrible mistake while adding sdram to my project (used output instead of bidirectional pin). Now everything is working like a charm :) Anyway many thx for your concern :) Regards @speak48 Probably you pixel buffer device has different name in your sopc system, maybe "pixel_buffer_0" or something like that... Many people have problems with this VGA stuff, so I attached some basic project including pixel buffer and simple software that draws some garbage on the screen. Hope some of You will find that useful. Project is for DE-2 board - Altera_Forum
Thanks a lot ronix5000 :)
I found my mistake finally.I generated 640*480 vga signal but first it took about 1000-2000ms to change all screen (100 Mhz nios core) and then I have made some modifications which reduce it to 117 ms (max. 9 fps).it is still not enough.I mean it looks like impossible to play a real-time video. Can this problem be handled somehow or should I change the video out core ? - Altera_Forum
are you using double buffering? maybe it will help...
- Altera_Forum
I don't know.what is double buffering? I have just connected 50 Mhz "up_ip_core"(s) and the "clock crossing bridge" with 100 Mhz nios system.
- Altera_Forum
ok but pixel buffer has ability of double buffering - it draws first buffer from memory while changing the second, then it draws second changing the first etc. You should analyze the code of pixel buffer to better understand this, cause in my opinion the only thing that determines fps is how fast you can rewrite SDRAM (or SRAM whatever).
