2010-04-16 11:54:39     High resolution and largest LCD touchscreen support by BF54x in ucLinux

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2010-04-16 11:54:39     High resolution and largest LCD touchscreen support by BF54x in ucLinux

Jon Ye (UNITED KINGDOM)

Message: 88525   

 

Hi

 

Was wondering if anyone can shed some light for me in the following questions:

 

1.) What's the highest resolution that a BF54x (since it has pixel compositor) can support under ucLinux? The one I see so are rather low resolution. Will ucLinus be able to run a 720i or 1080i using BF54x? If not please advise which processor will.

 

ADI support came back and reported there is "no restriction" on resolution support by the BF54x but we are not sure if ucLinux has such drivers available at the moment? perhaps can perform upsampling in the DSP?

 

2.) Screen size, thinking of using a touch screen, between 10-12", is it possible to run ucLinux to support this on BF54x.

 

I'm planning to do some 2D and simple 3D plots on the LCD using QT.

 

Any comments or help is greatly appreciated.

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2010-04-16 13:47:47     Re: High resolution and largest LCD touchscreen support by BF54x in ucLinux

Robin Getz (UNITED STATES)

Message: 88528   

 

Jon:

 

ADI support is mistaken.

 

The latest datasheet for the BF548:

 

  www.analog.com/static/imported-files/data_sheets/ADSP-BF542_BF544_BF547_BF548_BF549.pdf

 

indicates (Table 40): that the min PPIx_CLK Period is 13.3 ns (or the max clock rate is 75MHz).

 

It says this in the manual as well. (page 26-6 of the 548 HRM).

 

When using the internal clock, the maximum frequency possible for PPIx_CLK is SCLK/2. When

using an external clock, the maximum frequency for PPIx_CLK is 75 MHz.

 

 

So - the size (x/y pixel) limit of the screen is determined by the required screen refresh rate, the number of pixels, and the max pixel clock. Assuming 1080i (or fields of 1920 pixels of 540 lines, or 1036800 pixels), with a 60Hz refresh - is 62208000, or 62.2MHz (under the 75MHz limit).

 

However - there is also the question of where you store the image - (the bandwidth question) if it is in external memory - that is 62208000 pixel fetches per second - assuming 24-bit colour, that is 186624000 bytes per second - or 178 Megabytes per second on the DDR2. - which is close to the pratical limit of DDR2 (if anything else is going on in the system - ie. you are running from cache).

 

It depends alot on the screen specs (refresh rate), and what else is going on in the system (memory bandwidth).

 

I'm not sure there is a yes/no answer.

 

-Robin

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2010-04-16 16:38:55     Re: High resolution and largest LCD touchscreen support by BF54x in ucLinux

Jon Ye (UNITED KINGDOM)

Message: 88533   

 

Hi Robin

 

Thanks for the info. You are right, there don't seems to be a straight forward yes/no.

 

Was wondering do you know the limits of ucLinux on LCD touchscreen display. Being cautious, I just don't really want to dive into the investment with ucLinux and after a few months knowing that it may not work.

 

Jon

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2010-04-20 16:08:59     Re: High resolution and largest LCD touchscreen support by BF54x in ucLinux

Robin Getz (UNITED STATES)

Message: 88665   

 

Jon:

 

From a pratical standpoint - if the display refresh is slow enough - I have seen people run 720 (but I don't know if it was i or p).

 

-Robin

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