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TMDS1204: HDMI RX Detection Issue

Mohammed Arshad M
Prodigy 110 points

Part Number: TMDS1204

Hi Team,

We are using the TMDS1204IRNQR IC as a redriver on the HDMI RX side. However, when connecting an HDMI cable to a 4K laptop, the RX is detected successfully, whereas it is not detected when connected to a 1080p laptop.

Could you please help us identify the possible cause of this issue?

  • 0
    TI__Mastermind 37965 points

    Hi Mohammed,

    To clarify, the TMDS1204 is on a display (sink-side application) and when you connect this to different sources (laptops) one works whereas the other does not?

    When connecting to the 1080p laptop, can you go into the display settings on the laptop and see a second monitor attached? It should show in this interface on windows 11:

    If not, can you check that HPD is showing the correct value? You can probe the HPD pin on the HDMI connector or near the HPD_OUT of the TMDS1204. This should be high on the sink side while plugged in.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 110 points

    Hi Shane,

    The HPD pin of the HDMI connector measures 4.78 V, while the HPD_OUT pin of the TMDS1204 measures 4.12 V. But the signal is not getting detected in 1080p laptop.

    Regards,
    Arshad

  • 0 in reply to Mohammed Arshad M
    TI__Mastermind 37965 points

    Hi Mohammed,

    So in the display settings you are unable to see a second screen? Even if the video signal is not displaying a valid HPD and AUX should show that a monitor is present.

    If HPD is valid, can you probe the AUXp and AUXn lines while the laptop and monitor are connected? This should be probed near the DP connector. AUXp should have a DC voltage around 0.3V while AUXn should be around 3V. 

    Best,

    Shane