Is it possible using DMA to read the second half data from DCMI.

[mthanh2602]

Hello everyone.

I want to use only CPU to read and process VGA image with YUV format from camera. It's mean we have 640*480*2 = 600kbytes each frame and this is more than the 500 kbytes memory of CPU that I use. (I want to transfer directly data from DCMI to CPU by DMA without using any other RAM.)

So I think is it possible if first step I read the first half data, process it and the second step for the remain data?

But I don't know this ideal is posible or the right way to change the DMA configure? It's really complicated for me.

Many thanks for any helpp!!!!

[waclawek.jan]

> So I think is it possible if first step I read the first half data, process it and the second step for the remain data?

No, the data have to be stored somewhere.

If the picture is absolutely stationary, you might perhaps try to experiment with taking first part of one frame and second part of a later frame, but depending you how exactly do you process the data the results may be unsatisfactory.

JW

[mthanh2602]

Hi JW. Thanks for your comment.

I had tried by configure the window size but It just efficient after whole data transfered from DCMI to CPU. So I think configure window with small size does not mean transfer data is smaller. 

Then I reduce the length data of DMA configure by VGA length/2, I got the first half of data. But unknow how to get the second half. 

I think I have to spend more time to search about prosess the data again. Thanks so much.