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DS90UB949-Q1EVM: Will display Test Patterns but not HDMI input

Part Number: DS90UB949-Q1EVM
Other Parts Discussed in Thread: DS90UB949-Q1, ALP

HI, I have a DS90UB949-Q1 EVAL Board connected to a display that contains the DS90UB948 deserializer.  This display has a dual twisted-pair input.

I have been able to use the ALP GUI to generate test patterns in 1920x1080p at 60 hz refresh rate.

These look good.

My intention is to run HDMI from my laptop into the 949 then generate the LVDS signals into the display.  However, that link is not working.  Although the laptop recognizes the Eval Board as a display at 1920x1080 resolution.  The information screen on the ALP software indicates that the Eval Board is recognizing the display's deserializer.

It looks like the 949 can communicate with the display and the laptop, but there is a connection between HDMI and LVDS that is missing...

Can you point me in a direction to start looking for the correct setup?  I'm using the default settings on the Eval Board.


  • Hi David,

    Thanks for reaching out.

    In the APL GUI,

    1. In the HDMI tab, what do the "HDMI Status" and "FPD3 Status" show?

    2. In the Register tab, what does register 0x0C "General Status" show?

    3. In the Remote Register tab, what does register 0x1C "General Status" show?



  • Hello Solomon,

    Thanks for the reply.  Here are screen shots of the GUI and various registers.



    Here is the Information tab:

    Here is the HDMI tab:

    Here is Register 0x0C:

    Value = 0x07

    Here is the Remote Register tab for 0x1C:

    Value = 0x00

    Looks like SIGNAL DETECT = 0, or Serial Input not detected (even with Test Pattern showing on Display)

    Here is the Test Pattern tab:

  • Hi David,

    Thanks for the prompt feedback.

    Looking into the HDMI tab, it looks the "FPD3 Status" is not as expected. Something is not correct. 

    It looks like the problem is mainly from the deserializer side. One thing I noticed in the shared screenshot of "Remote Register" tab is that it lists a part number for DS90UH926 deserializer instead of DS90UB948 (see below)

    Also, the register description matches DS90UH926 device instead of DS90UB948. I was expecting to see something like this (see below):

    So, could you confirm if the deserializer device is actually DS90UB948 and not DS90UH926?




  • Hello Solomon,

    I can get the GUI to recognize the deserializer in the display as a DS90UB948 depending on how I set up the HDMI and/or Test Pattern tests.

    But, I can also set it up where it will detect as a DS90UB928...

    Here is the remote register 1C: = 2B

    Here are settings supposedly for the Display using the DS90UB949

    Here are settings expected for the deserializer DS90UB948:

    So, it appears that there is a DS90UB948 deserializer in the display.  There is supposed to be one.

    This is in an automotive application.  The display also has a connector on the back with +12V Power, GND, and two CAN (+/-) signals.  There is also a connector for the two LVDS (FPD-LINK) twisted pairs.  The main body controller issues wake-up CAN messages to the display which powers it up.  The Head Unit (Radio) then starts issuing FPD-LINK video to the display and works fine.

    I can disconnect the serial cable while the display is still connected to power/CAN and plug it into the DS90UB949 Eval Board and display Test Messages.  At the same time, I can set up the HDMI to be in 1920x1080p (2-ch) mode, and my laptop (connected to the HDMI) will recognize the Eval Board as a 1920x1080 external display.

    But, I cannot get the laptop's HDMI video to show up on the radio display screen.  But, I can generate Test Patterns very well.  However, I have to set these up with Internal clocking and 1920x1080p setting.

    Hope this helps.



  • Hi David,

    Thanks for the confirmation.

    To try to help narrowing down the issue, please do the following:

    1. Check if you are running the latest ALP SW by clicking on "About this Program" under the Tasks/Help panel. The Built on should match the following:

    2. After that, revert all programmings of any register and use the datasheet default register values. You should be able to get end to end video without programming any registers at all (assuming that the devices are strapped correctly). 

    3. If you are able to establish the end to end video in step #2, then you can let us know what specifically you are trying to achieve with the device programming and what features you are trying to exercise? Based on that we can help you with doing the desire configuration.

    Best Regards,


  • Hello Solomon,

    Yes, I am running the 1.57.001 version.

    I am getting ready to try Step #2 above.

    Thank you!


  • Hello Solomon,

    Well, I tried to change as many registers as I could back to their reset (default) state. However, that did not change anything.  I am wondering now if the host (i.e. the automotive head unit) is also sending back-channel signals to the display to enable it to show HDMI signals.

    I can definitely create Test Patterns from the Eval Board, so that part of the system seems to be working.

    I am in contact with the customer to see if they can offer any more information on how to interface with this display.

    So far, my laptop recognizes the Eval Board, as well, as a "valid" display (1920x1080), but there is still a disconnect somewhere.



  • Hi David,

    Re: "I am wondering now if the host (i.e. the automotive head unit) is also sending back-channel signals to the display to enable it to show HDMI signals.”

    The back-channel is used for communication from display to the host and not the opposite. The host uses the forward-channel to communicate with the display.

    Re: "I am in contact with the customer to see if they can offer any more information on how to interface with this display."

    Okay, thank you for the update. Please let us know what you hear back from the customer and if any additional support is needed.