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AM1808 LCD Controller graphics Underflow issues

John Cuthbertson
Prodigy 20 points

Other Parts Discussed in Thread: AM1808

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We are preparing a graphics demo to run on the Logic PD Zoom eval board for this processor.

 We are having some trouble with LCD underflows. Here are the details:

1) Located graphics frame buffer(s) in external DDR2, base @ 0xc0000000

2) Used TI's own BSP code to configure LCD controller registers (raster mode).

3) In the master priority control registers, changed the LCD to highest priority (0). Left all other masters at the default priority.

 

Even with this change, we are seeing frequent LCD controller underflows, which permanently shifts the screen data. The questions are:

 a) Do you have a recommended settings for all the master priorities to prevent LCD underflows? Any other configuration that might be incorrect and causing this problem?

 b) When there is an LCD underflow, what is the best way to reset the LCD controller to get the screen data back into position?

  • 0
    TI__Mastermind 27585 points

    You might want to see this post which recommends some ways to solve their problem. Do you have the cache fully enabled, and are you using any compiler optimizations? Do these have any effect on your underflow issue? Thanks

    Jeff

  • 0 in reply to jc-ti
    Prodigy 20 points

    Thanks for the link. I read through that thread, but did not find any helpful information. We have the caches fully enabled and we are using the IAR tools.

    We are using the LogicPD AM1808 experimenter kit. I am having exactly the same issue described in that thread, i.e. the pixel that should be located at 0,0 is often shifted to some other location on the screen. I do NOT see the underflow bit being set in the LCD status register, but the screen stays shifted.

    I am using the TI BSP code to configure the controller, except I modified that to program the FIFO threashold value to 128 dwords as described in an errata note related to this problem.

    Is this an issue with this processor?  We need to get this resolved because we have a customer considering using this h/w solution and he would like to see something from us running on the Zoom kit before he makes his final decision.

  • 0 in reply to John Cuthbertson
    TI__Mastermind 27585 points

    Since you are working on the EVM, is it possible to send the project code for us to run here and debug for you? Thanks

    Jeff