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DS90UB949-Q1: HDMI frequency and pixel clock not stable.

Ilyas SIMSEK
Prodigy 20 points
Part Number: DS90UB949-Q1

Hi,
My setup is as below.

I tried this setup with two different PCs.

With the first PC, the setup works and there is an image on the screen.

All my setup is exactly the same but when I try it with another PC it doesn't work.
With the second PC, the setup not works and there is not an image on the screen.
Pixel Clock is changing and CRC error counter is increasing.

  • 0
    TI__Guru** 103215 points

    Hello Illyas,

    It seems to me that perhaps the second PC is unable to generate the specific 1280x720 timing you are running here? I see from your picture of the first setup, that the PCLK is ~107MHz instead of the typical 1280x720 resolution at 74.25MHz. So I assume that you are using some sort of custom timing here through the 949 or 948 EDID? I have encountered issues in the past before where non-standard custom timings are unable to be generated by certain PCs. 

    Also is this a direct HDMI connection inn both cases? Or is the second PC using some sort of conversion cable like Type C -> HDMI or DP -> HDMI?

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 20 points

    The first two images in the first post were of my correctly working setup. The EDID I created is for 108MHz and 1920x720. I changed the VTERM and the HDMI frequency stabilized. But although the Pixel Clock value is 108MHz (1920x720) in EDID, I observe 100MHz (1920x720) at the output and there is no image on the screen.

    I am using a Micro HDMI to HDMI converter.

    Best Regards.

  • 0 in reply to Ilyas SIMSEK
    TI__Guru** 103215 points

    Ilyas,

    This appears to be a PC problem to me, not 949. I still believe that the second PC is unable to correctly generate the custom timing you are advertising here while the first PC can. I have seen that kind of thing before with custom non-standard resolutions.

    Best Regards,

    Casey