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DM648 VPort startup capture problem in Y/C mode

dp
Intellectual 990 points

I use DM648 video port to caputre yuv image data in Y/C mode. The problem I met is as below:

1. After the dm648 board is power on, the vport cannot capture the first three images.  

2. when the port is reset and reconfigure, the vport  cannot capture the first three images, too.

 The yuv image source is 70ms per frame.  We measure the timing difference between the vport reset signal and the first captured data signal,  which is about 200ms that is the total time of three images.

 

What I want to know is:

1. why vport cannot capture the first three images? the vport silicon errata, or the vport driver problem ?

2. how the vport do the startup synchronization in Y/C mode?

3. what behavior will lead to startup synchronization?  disable and re-enable VCEN ? or need to reset vport?

 

  • 0
    TI__Expert 4935 points

    Answers below:

    1. VPORT and VPORT driver are designed to capture continuous video data. What is the usecase to capture the first three frames after powering-up the board? As long as no frames are dropped after starting the VPORT/driver, it should meet all the video use cases.

    2. Below is the start-up sequence,

        a. Reset VPORT (not needed for restart)

        b. Disable EDMA events from VPORT (set BLKCAP bit to 1 in VC_CTL register)

        c. Set EDMA and enable EDMA channels

        d. Enable VPORT capture by setting VCEN bit to 1 in VC_CTL register

        e. Enable EDMA events by clearing BLKCAP it to 0

    3. Steps b, c, d and e is needed for startup sync. This sequence will take two frame period. And when you restart it will take one more frame period. And thus restart of VPORT driver will take three frame period.

     

  • 0 in reply to Sivaraj R3681
    Intellectual 990 points

    We use dm648 to make a camera to monitor  abnormal condition.  The dm648 don't capture until something happens.

    So dm648 cannot drop any frame.

    The video port dropping the first three frames in y/c mode make the dm648 cannnot work in y/c mode.