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DS90UB928Q-Q1: Pixel clock issue on DS90UB928

Zhanpeng Li
Intellectual 2140 points
Part Number: DS90UB928Q-Q1
Other Parts Discussed in Thread: ALP

Hi team,

met an issue on evluation DS90UB928:

system block below:

The problem now faced:

difference ALP data read on PCLK between 928 and 949:

The output setting on PC Side:

Support need:

could you help give some advice to adjust the PCLK on 928 to PC side output setting

BR

Brandon

  • 0
    TI__Guru** 103215 points

    Hello Brandon,

    This is expected behavior. The PCLK frequency detection circuit on the 928 side is generally less accurate than the 949 side since they use a different mechanism on each side to detect the clock rate. There is no issue for these to report different frequencies, and the actual measured frequency of the PCLK on each side will be the same if you were to check on the oscilloscope.

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    TI__Intellectual 2140 points

    Hi Casey,

    actually we faced a problem that we could not get signal or image from HUD side. i could attached the register related below, could you help check the reason or root cause?

    System block:

    Signal requirement from DLP230:

    Parameter on PC side:

    Register information on 929 and 928

    Register related.docx

    Could you help analysis?  Thanks so much!

    BR

    Brandon.

  • 0 in reply to Zhanpeng Li
    TI__Guru** 103215 points

    Hey Brandon,

    One thing I noticed is that the source is providing 30 pixels for the horizontal front porch but the display wants 40. Can you please make that adjustment? Also what is the expected HSYNC/VSYNC polarity from the DLP230? Other than that, it looks like from ALP and the reg dumps that the video chain between the SERDES is working and is at the correct PCLK rate. Is there some programming which needs to be done of the DLP230?

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    TI__Intellectual 2140 points

    Hi Casey,

    we found that there are other connection device with DS90UB928, and it address is 0x34, which is shown in 949.

    1)is there any influence to impact the signal link?

    2) after we seting the 928, we power reset the 949 and the video signal could be shown from 928. but the ALP display state still be desplink unlinked.

    i need to setting the 949 through I2C, would you help analysis the above situation?

    BR

    Brandon 

  • 0 in reply to Zhanpeng Li
    TI__Guru** 103215 points

    Hello Zhanpeng,

    Are you saying that the 928 has the same I2C address as another device on the I2C bus? As long as the I2C addresses are different, then it is ok and will not affect operation. Can you share the screen shot of the new setup you are asking about where the display video is shown but the device status reports unlinked in ALP?

    Best Regards,

    Casey