2008-01-08 10:24:54     Problems with NEC 6448 LCD on a 561 custom board

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2008-01-08 10:24:54     Problems with NEC 6448 LCD on a 561 custom board

Bill Fassler (UNITED STATES)

Message: 49354    We have a custom board based on the 561 DSP with a NEC 6448 LCD connected to it. We developed a driver for the EZ-KIT AV-extender board that worked fine. When we now modified this driver to the new board the display picture jumps sideways from time to time. Even if we only write one frame to memory that is going to be displayed and let the DMA continuously transfer the same data to the PPI/LCD the picture jumps. Could there be a problem with the DMA providing the data in a timely manner to the PPI device or could the problem be related to interrupts?

 

We are running the DSP at 589 MHz and the system clock at 117 MHz.

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2008-01-08 11:22:09     Re: Problems with NEC 6448 LCD on a 561 custom board

Bill Fassler (UNITED STATES)

Message: 49356    Through some trial and error it appears that when we do not start the ethernet in the kernel, this does not happen.  I am assuming it may be DMA related.  I am using the SMSC911x driver in the kernel.  Even after examining the code, I cannot seem to find which DMA channel it is using since on our BF561 custom board we have two PPI and two DMA channels. Our LCD is running on channels PPI0/DMA0.

 

We are looking into changing IRQ priorities, but if anyone could shed some light on what DMA channel the SMSC911x is using in the kernel and/or how we may address this problem please enlighten me.

 

Bill

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2008-01-08 15:38:36     Re: Problems with NEC 6448 LCD on a 561 custom board

Robin Getz (UNITED STATES)

Message: 49368    Bill:

 

I don't think the standard SMSC911x driver uses any DMA - only core reads/writes.

 

-Robin

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2008-01-09 04:14:03     Re: Problems with NEC 6448 LCD on a 561 custom board

Lars Weber Rasmussen (DENMARK)

Message: 49383   

 

Hi Bill!

 

You need to make sure DMA has higher access priority to ext bus than core ( DMAPRI0 bit needs to be set in  EBIU_AMGCTL ).

 

On the BF537 SCLK needs to be higher than 125 MHz ( we run 131.25 Mhz ) to get a stable display. Could be the same for BF561. You can also try to lower the PPICLK to the minimum frequency the display can accept.

 

BR

 

Lars

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2008-01-09 11:05:22     Re: Problems with NEC 6448 LCD on a 561 custom board

Bill Fassler (UNITED STATES)

Message: 49403    The version of the driver we use, is using DMA. However, even if we do not use the DMA we experience the same problem. The more traffic on the Ethernet port - the more problems with the display...

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2008-01-09 16:39:38     Re: Problems with NEC 6448 LCD on a 561 custom board

Robin Getz (UNITED STATES)

Message: 49418    Bill:

 

Have a look at:

 

http://blackfin.uclinux.org/gf/project/uclinux-dist/forum/?action=ForumBrowse&forum_id=39&_forum_action=ForumMessageBrowse&thread_id=25161

 

This has _nothing_ to do with DMA, or CDPRIO.

 

-Robin

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2008-01-09 18:22:52     Re: Problems with NEC 6448 LCD on a 561 custom board

Bill Fassler (UNITED STATES)

Message: 49420    Robin - We've been noodling with this all day.  We now see that the value we had in asynch bank 3 was not right which apparently played a part in this, but indisputably Ethernet is involved somehow because we NEVER see the problem when we do not enable Ethernet.

 

Perhaps another day of exploratory noodling and I'll figure it out.

 

Bill

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2008-01-10 10:04:11     Re: Problems with NEC 6448 LCD on a 561 custom board

Robin Getz (UNITED STATES)

Message: 49446    Bill:

 

Did you read through the entire thread I posted - it says exactly why ethernet is a problem for you.

 

-Robin

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2008-01-10 11:18:32     Re: Problems with NEC 6448 LCD on a 561 custom board

Cyril HAENEL (FRANCE)

Message: 49448    Bill, Robin is right, it's exactly the same problem that I had.

 

If you modify the read functions to set interrupt off/on on each byte sent, it should correct your problem.

In my case I have not tested because on the final application I don't need network connection, I use it only for developpement purpose.

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2008-02-07 05:06:39     Re: Problems with NEC 6448 LCD on a 561 custom board

Patrick Mc Donnell (IRELAND)

Message: 50800    Hi Lars,

 

I am currently undertaking a Research Masters (MEng) in Waterford Institute of Technology here in Ireland. For my MEng I am using a Blackfin, ADSP-BF537 EZ-KIT LITE, with an Blackfin A-V EZ Extender to try implement a generic, open source digital dashboard for use in the automotive industry.

 

I read your post, saying that you have developed a driver for the extender board for the BF537. I was wondering if I could get this driver off you for use in my project. I can you assure you that the use of this driver would be for educational purposes only.

 

Regards,

Patrick

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