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Linux/DS90UB929-Q1: DS90UB929 HDMI HPD signal is always low

user4334556
Prodigy 20 points
Part Number: DS90UB929-Q1

Tool/software: Linux

Hi:

1. current mode select:

2. refer the datasheet register settings:

3. following is this part of schematic:

4. when i disconnect HPD signal to HDMI source, and pull up HDMI source HPD force, HDMI source TMDS signal correctly output. at this time, i read the 0x5a register value is 0x02(NO_HDMI_CLK).

5. the HPD signal status is always low, how can i make HPD signal from low to high?

  • 0
    TI__Guru** 103215 points
    Hello,

    Is your 949 connected to a downstream deserializer? The HPD signal will only get asserted if there is lock between 929 and the downstream deserializer. You can also force HPD low or high with the following commands:

    2. De-assert HPD with the following commands:
    a. 0x48 = 0x01
    b. 0x49 = 0x00
    c. 0x4A = 0x00
    d. 0x4B = 0x01
    e. 0x4C = 0x00
    f. 0x4D = 0x00
    g. 0x4E = 0x00


    3. Assert HPD:
    a. 0x48 = 0x01
    b. 0x49 = 0x00
    c. 0x4A = 0x00
    d. 0x4B = 0x01
    e. 0x4C = 0x00
    f. 0x4D = 0x00
    g. 0x4E = 0x01


    Best Regards,
    Casey
  • 0 in reply to Casey McCrea
    Prodigy 20 points

    Hi,

    thx, it's work well now.

  • 0 in reply to user4334556
    TI__Intellectual 1830 points

    Hi Casey,

    My customer have similar question as above. It seems HPD could be forced high as you mentioned above.

    My customer want to force HPD high, while they also want to check if RX_5V could be not used, as they have no 5V rail on board, but 3.3V and others.

    My understanding is if HPD could forced high to tell SOC ready to output video, then I might could connect HPD(OD structure) to 3.3V pull up, while do let RX_5V floating ?

    As HPD output is 2.4V-5.3V range ?

    Thanks.

  • 0 in reply to Rocson He
    TI__Guru** 103215 points

    Hello Rocson,

    The RX_5V must be 5V as per the recommended operating conditions for the device so I would not recommend trying to do this. However it should be possible to not connect HPD from the processor into the 949 at all if the customer wants to force the HPD high going into the SoC through some other means. 

    Best Regards,

    Casey