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TMDS181: DDC snoop for Source side application

Takahiro Saito
Expert 5345 points
Part Number: TMDS181

Hi team,

The datasheet only shows sink side application for DDC snoop configuration like Figure 35 and 36.

Could you make sure if TMDS181 can also use DDC snoop configuration for source side application?

If it's acceptable for source configuration, SCL/SDA_SRC is tied to GND and SCL/SDA_SNK is directly connetcted to DDC_SCL/SDA of processor. Is that correct?

Regards,

Saito

  • 0
    TI__Expert 5345 points

    Hi team,

    Could you also check whether source side application can uses HPD bypass configuration?

    If okay, HPD_SRC is tied to GND and  HPD_SNK is connected to HPD of processor side directly and HPD_SNK is connected to 5V and connector.

    Is that correct?

    Regards,

    Saito

  • 0 in reply to Takahiro Saito
    TI__Guru**** 154691 points

    Saito-san

    Would you please further clarify the questions? 

    The Source needs to see the HPD from and communicates with the Sink through the DDC. How does the Source handle these two functions without connecting to the Sink?

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Expert 5345 points

    Hello David-san,

    Sorry for the unclear question.

    I know the source need to see HPD and communicate with sink by DDC.

    I just want to confirm whether TMDS181 can use DDC and HPD snoop for Source side application.

    Also, I'm appreciate if you could explain me the setup for DDC ande HPD snoop for Source side application.

    Regards,

    Saito

  • 0 in reply to Takahiro Saito
    TI__Guru**** 154691 points

    Saito-san

    The connection is the same as the sink side application. 

    The SDA/SCL from the source is connected directly to the SDA/SCL of the connector. The TMDS181 will need its SDA_SNK and SCL_SNK pins connected to this link in order to correctly configure the TMDS_CLOCK_RATIO_STATUS bit. SDA_SRC and SCL_SRC must be connected to GND. If the voltage levels for DDC between the source and sink is different, 3.3 V vs 5 V, then you need to use an I2C level shifter. The I2C level shifter can also be used to isolate the DDC capacitance. 

    The HPD from the source is connected directly to the HPD of the connector. The TMDS181 will need its HPD_SNK pin connected to this link and leave HPD_SRC pin floating. Some sink could have leakage voltage on the HPD when it is off, so you may need a FET switch to isolate this leakage voltage.

    Thanks

    David