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DS90UB941AS-Q1: 941 can't access 928 through i2c

min.du
Prodigy 10 points
Part Number: DS90UB941AS-Q1
Other Parts Discussed in Thread: ALP

Hi,

    We debug the 941/928 display, Soc -> 941 -> FPDLINK III -> 928 -> LVDS Screen

    The 941 can read and write normally, the 928 can't. But The 948 instead of 928 is ok.

    The MODE_SEL configuration of the 928 is shown below:

    

    The MODE_SEL0 & MODE_SEL1 configuration of the 941 is shown below:

    

    

    The 941 configuration sequence is as follows:

    i2cset -fy 3 0x0c 0x01 0x08

    i2cset -fy 3 0x0c 0x5b 0x01

    i2cset -fy 3 0x0c 0x03 0x9a

    i2cset -fy 3 0x0c 0x01 0x00

    The following 941 register values:

    

   The following 928 register values:

    

    BR,

    Thanks

  • 0
    TI__Genius 16630 points

    Hi Min,

    Are you using TI EVMs or is that your own application design?

    928 doesn't support Coax configuration , is your 941AS HW setup to Coax or STP?

    Are you sure your mode straps are set correctly on 941AS and 928?

    Example - I see on 941AS Register 0x13 = 0x8B which is mode_sel1 = mode0 not like what you highlighted below. Can you please double check all of your mode straps to confirm you have the correct straps. 

    Also, register 0x6 should recognize 0x58 (Des address) but it's not I see 0x0

    Register 0x5A which tells you that link is ready should be reading 0x92 if no DSI input is applied not 0x9 

    min.du said:

      i2cset -fy 3 0x0c 0x01 0x08

        i2cset -fy 3 0x0c 0x5b 0x01

        i2cset -fy 3 0x0c 0x03 0x9a

        i2cset -fy 3 0x0c 0x01 0x00

    In your script you mention that you are setting reg 0x1 back to 0x0 but the reg dump shows 0x8 still?

    Do you have access to TI's ALP software?

    Regards,
    Fadi A.

  • 0 in reply to Fadi Abdulhameed
    Prodigy 10 points

    Hi Fadi A

        Happy new year!

        I'm sorry for taking so long to reply you because of the Chinese Spring Festival.

        I'm sure the 941AS is set to STP mode.

        If the 941AS needs to be connected, how do I configure the MODE SEL of 928?

        We checked RIN+/- according to the figure below and found no anomalies.

        

         The 928 lock signal is high.

         We don't access to TI's ALP software.

         BR,

         Min

  • 0 in reply to min.du
    TI__Genius 16630 points

    Hi Min,

    Happy new year!

    min.du said:
     The 928 lock signal is high.

    If lock is high that means your mode straps are set correctly. Also it means you have video on the 928 output. 

    So your video is ok but your remote I2C communication from 941AS to 928 is not working? The I2C master (SoC) is not able to communicate with 928 through 941AS? Or are you trying to communicate to 941AS through 928 ? What direction are you trying to access I2C? Or is the issue with local I2C of 928?

    Is this issue happening on all systems or only a single system what is the scope of this issue? 

    Does the issue always occur or sometimes? Is it intermittent, etc.?

    How many systems have been produced and how many are seeing this failure?

    Regards,
    Fadi A.

  • 0 in reply to Fadi Abdulhameed
    Prodigy 10 points

    Hi Fadi A,

        Yes. The I2C master (SoC) is not able to communicate with 928 through 941AS. And the I2C master (SoC) is not able to communicate with 941AS through 928 too. We tested multiple 928 boards and SoC boards with the same problem.

    BR,

    Min

  • 0 in reply to min.du
    Prodigy 10 points

    Hi Fadi A,

        We now default to raising the BISTEN pin. When we pull down the BISTEN, the I2C master (SoC) is able to communicate with 928 through 941AS.

    Now the screen is working properly.

    BR,

    Min

  • +1 in reply to min.du
    TI__Genius 16630 points

    Hi Min,

    BISTEN pin will enable BIST mode which is a high speed internal link test. During this test the FPD-Link will be driven at speed with an internal pattern so remote I2C transactions won't be passing through until BISTEN is pulled low to exist the test mode. 

    This test is useful in the prototype stage to check link robustness, etc. but for normal system operation please have it pulled low at start-up so you don't enter this test mode. 

    Regards,
    Fadi A.