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TMDS1204: TMDS HPD_IN and HPD_OUT in sink application

venkatesh ponduri
Prodigy 60 points
Part Number: TMDS1204

Hi Team,

I am using TMDS1204 in my design. I2C communication is not responding.  Also HPD_IN connection following same as application circuit given in datasheet. I.e. HPD_IN is connected to connector with pull up of 5V (hdmi connector not on board 5V). If I connect loopback cable then I2C starts responding. So below are my queries

1. Is there any relation between HPD_IN and I2C bus to be active?

2. In sink application, HPD_signa is output from SoC. So What is exact HPD_IN and HPD_OUT connection if I use TMDS1204 as sink application? I believe HPD_IN should drive by SoC and HPD_OUT should connect to HDMI RX connector. 

Also attached my circuit diagram for your reviewTMDS1204_schematics.pdf

Thanks,

Venkatesh

  • 0
    Prodigy 60 points

    Adding point .. I am using TMDS1204 in SINK path

  • 0 in reply to venkatesh ponduri
    TI__Mastermind 23865 points

    Hey Venkatesh,

    Would this be a correct block diagram for your system?

    venkatesh ponduri said:
    1. Is there any relation between HPD_IN and I2C bus to be active?

    For DDC communication to take place between a source and sink HPD must be set high at the source. 

    venkatesh ponduri said:
    2. In sink application, HPD_signa is output from SoC. So What is exact HPD_IN and HPD_OUT connection if I use TMDS1204 as sink application? I believe HPD_IN should drive by SoC and HPD_OUT should connect to HDMI RX connector.

    In a sink application HPD_IN should be the 5V HPD coming from the panel, and HPD out should be going to receptacle.

    Let me know if you need more clarification.

    Best,

    Vishesh Pithadiya

  • 0 in reply to Vishesh Pithadiya
    TI__Mastermind 23865 points

    Here is a reference schematic. I will have a look at the one you sent and get back to you shortly.

  • 0 in reply to Vishesh Pithadiya
    Prodigy 60 points

    Hi Vishesh,

    Thanks for response.

    1. I am not talking about DDC I2C. We have other I2C to program internal registers that one. That pin-21 and 22. Is there any relation between HPD_IN and normal I2C?

    2. You mentioned Panel in your block diagram. Panel means SOC/processor?

    3.In Sink application usually HPD should be output from SoC right. means SoC should drive this signal to outside world right. FYI Below is my block diagram

     

    Thanks,

    Venkatesh

  • 0 in reply to venkatesh ponduri
    Prodigy 60 points

    Also there is not difference between HPD_IN and HPD_OUT connections in both source and sink application circuit given in Datasheet. Can you pls check once. Below is image captured side by side.

     

    From application circuit, both case HPD_OUT connected to SoC/FPGA means HPD signal is always input in both Tx and Rx application.  But this is not the case i believe. 

    In Tx application, HPD signal is input 

    In Rx application, HPD signal is output.

    pls check the HPD_IN and HPD_OUT connections in SINK application once

  • 0 in reply to venkatesh ponduri
    TI__Mastermind 23865 points

    Hey Venkatesh, 

    Here is the schematic review: 

    - ESD looks ok too

    TMDS1204_Schemtic_Review_Intel_RevA(4_11_2024).pdf

    venkatesh ponduri said:

    3.In Sink application usually HPD should be output from SoC right. means SoC should drive this signal to outside world right. FYI Below is my block diagram

     

    Yes this is correct, I had my arrows going in the wrong direction the previous diagram, so I removed it. 

    venkatesh ponduri said:

    2. You mentioned Panel in your block diagram. Panel means SOC/processor?

    Yes

    venkatesh ponduri said:

    1. I am not talking about DDC I2C. We have other I2C to program internal registers that one. That pin-21 and 22. Is there any relation between HPD_IN and normal I2C?

    As long as the device is powered up control I2C communication should work as normal independent of HPD.