Vmodcam project's read and write batches

[takieddine]

Hi, 

Could you please explain how the read and write batches are used in the frame buffer controller ?

[jpeyron]

Hi @takieddine,

I downloaded the VmodCAM_Ref_HD Demo_12 form here. Looking at the VHDL code which can be found here: VmodCAM_Ref_HD Demo_12\VmodCAM_Ref_HD\FBCtl.vhd the file description states that the FBCtl is a frame buffer controller using a DDR2 memory for physical storage. The controller allocates two separate frame buffers each one with a stream write FIFO interface for video sources and one stream read only port for a video consumer. MSEL_I configures the read port to stream data from either frame buffer. The VHDL code has good comments to describe what is going on in each code block. There is a more generic description of the project in the readme.txt in the project as well. Could you be more specific about what part of the FBCtl.vhd you would like explained.  I have also reached out to my co-workers to see if they have any input for you.  

cheers,

Jon

[takieddine]

Hi Jon,

I have three questions about the reference VGA  design, how do you select the size of the read and write batches ? 

constant RD_BATCH : natural := 16;
	constant WR_BATCH : natural := 32;

How do you choose the ending address in the frame memory buffer controller ? in the given code we have

if (pc_rd_addr1 = 640*2*480/(RD_BATCH*4)-1) then
					pc_rd_addr1 <= 0;

And why do you convert to p3_cmd_pr_addr like this 

p3_cmd_byte_addr <=
        conv_std_logic_vector(pc_rd_addr1 * (RD_BATCH*4),30) 

 

[jpeyron]

Hi @takieddine,

 

 

I have reached out to the creator of the project to get input about your question. Unfortunately they are away from the office. It might be up to 2 weeks before they are able to respond to this thread. I am very sorry about the inconvenience.

Thank you,

Jon

 

 

[Cristian.Fatu]

Hello,

Hoping that this might help you, I am sending you a demo application. It is a 3D Vision demo, based on VmdoCAM. Please note that this demo was not released, so it is not "polished".

https://www.dropbox.com/s/zoyo4ja8cbgzv2j/3D Camera Demo Project.zip?dl=0.

Good luck!

 

[takieddine]

Thank you Cristian, In the documentation it is mentioned that  this project applies to rev D of the board, I have REV C can I use it ?

[Cristian.Fatu]

Yes, it is stereo vision implementation. Please read the documentation inside the zip file to find more, as I know very few about this project.

[Cristian.Fatu]

The last version of VmodCAM is rev. C. Anyway, this example is the only one we have, so try to use it "as it is".

When you add new questions, please add new posts, as editing the previous posts is not a good approach because existing answers seem to "float" over replaced questions.

[takieddine]

I read spartan 6 memory controller documentation, and I understood that the batches sizes are chosen according to the size of the FIFOs inside the memory wrapper; my question now can I use small BRAM FIFOs to buffer the video feeds from VmodCam, lets say I use size of 32 for both batches.