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DS90UB941AS-Q1: questions about 941/926&948

user5607380
Prodigy 70 points
Part Number: DS90UB941AS-Q1

Hi expert,

We use 941 connect two display with Asymmetric Splitting With Cropping， one use 926(320*320); one use 948(1920*640), below is simply diagram:

Now we have displayed the color bar normally on 320*320 LCD  through the built-in test pattern of 941.

we have below questions need your help:

1、When Soc output DSI to 941, 926 output No DE signal，what could be the cause?

2、The D_GPIO[0:3] could pass through to 926 GPIO[0:3]  only if 18bit selected of 941？Is there any way to achieve 926（18bit）+948（24bit）display？

  • 0 in reply to user5607380
    TI__Mastermind 19720 points

    Hi 

    Here is a good resource when debugging the 941AS's DSI: 

    1. what DSI mode are you using? (Non-Burst Mode With Sync Pulses, Non-Burst Mode With Sync Events or Burst Mode)

    2. What register were you setting? 

    3. Is there any way to achieve 926（18bit）+948（24bit）display？

    you could achieve this by disconnecting the 2 LSB's of each RGB Parallel to "convert" 18 bit from 24 bit.

    Regards,

    Michael W.

  • 0 in reply to Michael.Walker
    Prodigy 70 points

    Hi Michael,

    We found that increasing pclk>15M (by increasing the resolution to 640*640) can solve the problem of no DE signal，now there is a display on LCD，it seems like limited by LFMODE of 926.

    “you could achieve this by disconnecting the 2 LSB's of each RGB Parallel to "convert" 18 bit from 24 bit.”

    ->When we choose 24bit of 941 and disconnecting the 2 LSB's of each RGB，the D_GPIO[0:3] could not pass through to 926 GPIO[0:3], At this time, the measured 926 GPIO is still RGB data signal.

  • 0 in reply to user5607380
    TI__Mastermind 19720 points

    Hi 

    Yes, have you tried having the 926 in LFMODE?

    The 941 cannot send out 24 bpp data on one FPD-Link Port and 18 bpp data on the other FPD-Link port so it is not possible for the D_GPIO[0:3]'s to pass to the 926.

    Regards,

    Michael W.

  • 0 in reply to Michael.Walker
    TI__Intellectual 1490 points

    Hi Michael,

    What we want is a 24 bits data output from 941 and 941 DGPIO pass through to 926 GPIO.

    The 941 sends out 24bits data, we configured 926 as 18bits color mode (enable GPIO[0:3]).

    At this condition, the 941 DGPIO could not pass through to 926 GPIO.

    Please advise how we can address this problem.

    BRs,Shubiao

  • 0 in reply to Shubiao Wang
    TI__Guru** 103215 points

    Hello Shubiao,

    To utilize 926 GPIOs through the FC link, both 941AS and 926 need to be in 18 bit mode. But in this case 941AS can not support splitting 24 bit on one link and 18 bit on the other link like this. Both links would need to be in 18 bit mode. 

    Alternatively you could control the remote GPIOs via register control through I2C using the bidirectional control channel 

    Best Regards,

    Casey