2008-04-14 09:03:39     Problem about two PPIs working in the same time.

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2008-04-14 09:03:39     Problem about two PPIs working in the same time.

Wei Jiang (CHINA)

Message: 54201      Dear all,

  My hardware is BF561, I connected a LCD to PPI0 and a CMOS to PPI1.

  LCD works well when CMOS is not enable.

  But when the CMOS is enable, the image is absolutely messy. The whole picture moves randomly and quickly even I set the LCD-PCLK down to 4M and CMOS-PCLK down to 12M.

  I used three timers to attach the LCD interface. This means the PPI_CLK of PPI0 is connected to a timer, too. As we all know the PPI_CLK is really sensitive of noise so I think maybe there are something wrong about the clocks.

  I'm wondering if someone has do the same thing in BF561 boards. if do, please give me some advice.

  Thanks. Any clue is appreciated.

         Wei, Jiang

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2008-04-14 22:56:10     Re: Problem about two PPIs working in the same time.

Yi Li (CHINA)

Message: 54228    Are you using uclinux? Did you write your own driver?

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2008-04-15 04:00:41     Re: Problem about two PPIs working in the same time.

Ji Ma (CHINA)

Message: 54240   

 

I have ever done the application on bf561 below:

 

1.ppi0 cature the video with BT656 timing from video decode(720x576).

 

2.ppi1 output the video with BT656 timing to video encode(720x576).

 

3.both are 27MHz pixel clock.

 

If the timing is right on your board , I think you are writting a low efficiency driver or program.

 

best performance can be done get the notice beblow:

 

1.kernel and user space mmap reduce data copy ops.

 

2.manually refresh the display buffer , not be periodically.

 

3.less data capture ,less bus band waste.

 

4. less anywhere data copys.

 

5.DMA for critial data copy.like ppi to buffer, buffer to ppi , any other data copy are not necessary.

 

best regards.

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