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TMDS181: TMDS181 DDC in snoop mode by HW setting

Patty Chuang
Intellectual 1155 points
Part Number: TMDS181

Hi Team,

customer is having issues with TMDS181 setting. we have asked customer since TMDS181 implements clock stretching on its source side (pin 46 and 47), does the source support clock stretching? If not, then the design need to implement the TMDS181 DDC snoop mode.

Customer feedback that The HDMI I2C source is form PC. And how to set TMDS181 DDC in snoop mode by HW setting? 

Please help to comment.

Thanks!

Patty

  • 0
    TI__Guru**** 176651 points

    Patty

    Please refer to section 8.4.4 in the TMDS181 datasheet, particularly the note section on the DDC snoop implementation.

    The TMDS181 utilizes clock stretching for DDC transactions. As there are sources and sinks that do not perform this function correctly a system may not work correctly as DDC transactions are incorrectly transmitted/received. To overcome this a snoop configuration can be implemented where the SDA/SCL from the source is connected directly to the SDA/SCL sink. 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. Care must be taken when this configuration is being implemented as the voltage levels for DDC between the source and sink may be different, 3.3 V vs 5 V; See Figure 35 and See Figure 36.

    Thanks

    David