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DM6437 video output does not display color

user4544285
Prodigy 20 points

Use DM6437 chip.Software environment is dvsdk. The board is used for human tracking .Basic reference design is mainly used.

The problem is that the video output should be in color, but actually it is black and white. Experiment named color bar is done for the test. The principle of it is  DSP VPBE display color bars directly and then sent. And basically the program is no problem , but the result is still stay  black and white . Further testing, DSP DAC output is just black and white. The figure below is the  analog waveform measured.

To contrast ,I had colorful  colorbar waveform on other's board, substantially the same with me, below is another good colorful colorbar graphics . Because of the high precision for analog video signal , time is in 'us' level, so my wave ripple though is small, but relatively worse than others, I do not know whether my ripple waveform is relatively too large and there should be a straight line but mine has a little rise.Difference can be seen from the chart.

I set the output format to pal, display screen standard mode is optional, the selection is of course pal. In addition, the same board was done for two pieces, one of which is off after a very long time, and then when the power is on ,it displayed in color, but the color is very poor, then it becomes black and white again. The other one is always black and white .

What causes problems above? Does layout cause? Whether  there are some layout rules about analog video output ?Whether there are some related instruction manual?Please answer me! Thanks . PS:my Eglish is not very good ,if there are any grammar probloms,please acknowledge.thanks again!

  • 0
    TI__Mastermind 35645 points

    Hi,

    Thanks for your post.

    I guess, there could be chances of below:

    1.  There is a higher prirority thread that is basically blocking your display task from running as fast as you want it to.

    2.  If the video port backend is set up as a slave for clocks and syncs, and those clocks and syncs are slower than expected, this could cause the problem you are seeing.

    For more details, you could refer VPBE userguide as below:

    http://www.ti.com/lit/ug/spru952a/spru952a.pdf

    There is an app. report which would provide a brief video basics overview below:

    http://www.ti.com/lit/an/spraan0/spraan0.pdf

    Also, you could also walkthrough the below E2E posts which i hope, it would help you better:

    https://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/99/t/7403

    https://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/99/t/68947

    Thanks & regards,

    Sivaraj K

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  • 0 in reply to Sivaraj Kuppuraj
    Prodigy 20 points

    Thanks for your reply!

    But I still have some doubts.As for your first point ,you talk something about threads,but  the problems on our board  are  basically not  caused by  software.It should be due to some kind of hardware.The same program runs very well on someone else's borad.Secondly,if the clock delayed,that will only lead to a deviation of the phase, not result in the loss of color signal in output.Maybe I'll wait a while to get results which should be sent a time ago.

    Perhaps because of my personal knowledge limitation, many details are ignored by me.I hope you can give more explanation.Thanks again!