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Are there any example for HDMI => VGA converter that VGA reasult stored on BRAM also


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Dear everybody.

Thanks DIGILENT for their very nice demo on HDMI => VGA converter on ZYBO.

I would like to use ZYBO to convert input HDMI image to VGA output and also write result to BRAM for later use.

PS should also work in parallel reading those result out (from memory) and written to somewhere via Ethernet.

As my understanding, the demo given by DIGILENT for HDMI => VGA converter uses no BRAM.

I would like to know if some similar (to my purpose) demo is available and where on the design should I modify to achieve the above purpose.

Best Regards,

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On 2/2/2017 at 7:50 PM, miguel_rodrigues said:

A while ago I created this tutorial that is somewhat related to parts of this (http://www.instructables.com/id/Zybo-AXI-DMA-Inside-Embedded-Linux/).

Dear miguel

In your tutorial, you said that the code modified during OS preparation will divide the DDR memory into 2, a half for OS, and the other half for DDR. "What this does is make Linux see only 256MB of DDR memory (instead of all the 512MB capacity that the DDR has). This is required in order to have a chunk of memory (in this case, 512-256=256MB) reserved for using the AXI DMA engine.". It seems that OS will not touch to the second half.

Are there any possibility to make OS reads the second half of memory but still allows user HW writes to it. Problem of read during write might occur but can be controlled if I divide the user HW memory to several banks and swapping them for read and write purpose.

Problem on rebuild SDK project:

After replacing the user SDK generated fsbl_hocks.c file by the one taken from the zybo_base_system for mac address setting, I have problems with the include of "xiicps.h" and "xiicps_hw.h". I found them on internet and added to the user SDK project but now it has 'XPAR_PS7_I2C_0_DEVICE_ID' undeclared (first use in this function) error occurs in fsbl_hocks.c.

I am not sure which I2C this is related to but in my HW design, I replaced the control of PS on I2C of HDMI by a HW version (simply by changing the pins connection) to prevent OS from making HDMI to be output.

==========> I found out that the problem is the difference between the based system I used (xillydemo) and the zybo_base_system. I think I will need some elements generated for xillydemo project by xillybus.

I am sorry for many questions.

Yours,

Tuan

Edited by tuan
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Dear tuan,

 

I would suggest you to follow the tutorial first with the Zybo Base System from Digilent first and only if you succeed, try to adapt the tutorial to Xillybus.

 

Regarding your question:

 

  • "Are there any possibility to make OS reads the second half of memory but still allows user HW writes to it. Problem of read during write might occur but can be controlled if I divide the user HW memory to several banks and swapping them for read and write purpose. "

 

The user can read/write to all memory. But the OS kernel will only use the first half of the memory. You can not control which memory the OS kernel uses and thus, you need to make sure that the OS kernel only sees part of the memory. However, your programs will always be able to use the full memory space, which is what you want I believe.

 

Good luck ;)

Edited by miguel_rodrigues
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