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Visitor sorrowsnow
Visitor
6,521 Views
Registered: ‎05-01-2016

Read an write to the DRAM on a zynq device..

I have for a couple of months been struggling with interfacing the DRAM located on the PS side of my dev. board.

I am using the PL as a driver for the VGA port, which should display the images which the PS generates.  

My intention was to store the images which the PS creates into the DRAM, and the the PL read them from the DRAM, and then display them. The PS keeps sending new images, which is why the adress has to be kept updated. 

It seems silly to my that there is this big problem to interact between the PL and PS, which make me think that i may overlook something very simple.  


Clearly interfacing with a DRAM  shouldn't be a problem?... 


So... The million dollar question? How do interact with dram?

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4 Replies
Teacher muzaffer
Teacher
6,504 Views
Registered: ‎03-31-2012

Re: Read an write to the DRAM on a zynq device..

I am not sure where you are in the process by the description in your email but assuming you have an axi master in pl which reads the images from the address given by ps, there are two potential issues which you need to resolve:
* pl axi masters can only deal with physical addresses but ps programs potentially use virtual addresses (depending on your os, mmu confiuration etc) so you need to convert ps addresses to physical addresses.
* when ps writes to ddr, there is a chance that the data will be kept only in l2 cache and never make it to ddr so when the pl master reads from ddr, it won't see the actual data.
- Please mark the Answer as "Accept as solution" if information provided is helpful.
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Visitor sorrowsnow
Visitor
6,477 Views
Registered: ‎05-01-2016

Re: Read an write to the DRAM on a zynq device..

actually.. the VGA driver is the only thing which is working at the moment..  

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Visitor sorrowsnow
Visitor
6,472 Views
Registered: ‎05-01-2016

Re: Read an write to the DRAM on a zynq device..

Actually the only things which works is the VGA driver on the PL side.
It can display an hard coded images on the PL side, and thats it.

I still need someway to interface the DDR from the PL side, and a way to store the images the PS creates onto the DDR.
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Adventurer
Adventurer
1,624 Views
Registered: ‎11-19-2010

Re: Read an write to the DRAM on a zynq device..

I'd use AXI-4 interconnect and the VDMA IP (Video DMA)

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