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TDA4VM: Does TDA4's DP interface force output?

fengkai.yue
Prodigy 20 points
Part Number: TDA4VM

Tool/software:

I ran into a problem when I was using TDA4's DP interface to output video.
I have a DP interface screen and a type-c interface screen.
(1) I connect the DP interface of TDA4 with the DP screen and then turn on the power supply of TDA4, and the DP screen can display pictures.
(2) I connected the DP interface of TDA4 to the type-c screen with a DP-to-Type-C conversion cable and then turned on the power supply of TDA4. The type-c screen could not display the picture and indicated no signal.
(3) I first execute (1) and then do not power off the TDA4 and then unplug the DP screen and connect the type-c screen, the type-c screen can display the picture.
Does TDA4's DP interface force output?

  • 0
    TI__Genius 17710 points

    Hi,

    Due to a holiday, half of our team is currently out of office. Please expect a 1~2 delay in responses.

    Apologies for the delay and thank you for your patience.

    -Fabiana

  • 0 in reply to Fabiana Jaimes
    TI__Guru**** 450265 points

    Hi yue,

    We have not tested DP to USB-C connector. most likely, the connection is not detected and that's why DP output is not turned on. So please check what's required in this connector to detect the connection status. 

    Regards,

    Brijesh

  • 0 in reply to Brijesh Jadav
    Prodigy 20 points

    Hi Brijesh，
    The DP_HPD signal of the Type-C screen and DP screen behaves the same when connected.
    when plug in DP_HPD is high (3.3v) .when plug out DP_HPD is low (0v).
    I learn that the DP protocol reads some screen information through the AUX channel. Does this information affect the ability of TDA4 turn on DP output?
    Can we skip reading the screen information through AUX and force the DP to output the video stream?

    Regards,

    yue

  • 0 in reply to fengkai.yue
    TI__Guru**** 450265 points

    Hi yue,

    You would have to change the DSS driver code in PDK to ignore the aux communication errors. Please check the call to DP_LinkTraining API in packages\ti\drv\dss\src\drv\dctrl\dss_dctrlExtended.c.. 

    Regards,

    Brijesh

  • 0 in reply to Brijesh Jadav
    Prodigy 20 points

    Did the DP initialization and hot plug process print any logs? How should I view the log?

  • 0 in reply to fengkai.yue
    TI__Guru**** 450265 points

    Hi yue,

    No, but typically on hot plug detecting, link training is done. 

    Regards,

    Brijesh

  • 0 in reply to Brijesh Jadav
    Intellectual 691 points

    Hi Brijesh：

    Can you help you find out where the problem is by adding some logs or enabling debug logs?

    Regards,

    Shaoyu

  • 0 in reply to Shaoyu Xu
    TI__Guru**** 450265 points

    Hi Shaoyu,

    As i mentioned in the above post, the DP_LinkTraining API does the link training and then after successful execution of this training, output is started, so can you check if link training was successful?

    Regards,

    Brijesh 

  • 0 in reply to Brijesh Jadav
    Prodigy 20 points

    Hi Brijesh

    I checked the link training results and it was a failure. It returns 5(CDN_EIO) on the first call to DP_ReadDpcd() in the readSinkCapabilities() function.

    Regards,

    yue

  • 0 in reply to fengkai.yue
    TI__Guru**** 450265 points

    Hi Yue,

    ok, since you want to force the DP output, you would have to change the code to ignore this error returned from the link training API. 

    Regards,

    Brijesh