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SN65DSI83: DSI83 + ds90cf363b connectivity questions.

Part Number: SN65DSI83
Other Parts Discussed in Thread: DS90CF363B,

Hello everyone,

 

I opened this new thread to continue debugging the issues described on the tickets below.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1231429/sn65dsi83-lvds-screen-corrupted-when-using-the-dsi83

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1268835/sn65dsi83-lvds-corrupted-when-using-the-dsi83-follow-up

As mentioned on my previous threads, we are facing some sporadic visual glitches when using the following setup: i.MX8MM + DSI83 + ds90cf363b + LCD.

On my last two tickets we were suggested several software workarounds, unfortunately none of them worked since our sporadic issue is still visible 1/100 times the LCD is powered up.

After reviewing our hardware schematics, we saw that the SN65DSI83 is powered by a 1.8v power supply, meanwhile the ds90cf363b is powered by a 3.3v power supply, please refer to the attached picture.

 f1.zip

Could you please let us know if this could be an issue?

 

Looking forward to your comments,

Thanks, and best regards,

Esteban V.

  • Hey Esteban,

    Currently looking into this. Ill get back to you as soon as I can.

  • Hey Esteban,

    I don't think the different voltage supplies will cause any major impact in functionality. The more likely culprit would be excessive jitter at the DSI clock which the LVDS clock is based on. Can you send the register values of 0xE5 to see where the error is happening?

  • Hello Vishesh ,

     

    Thank you for your quick response, and for the clarification.

    Please find below an I2C register dump captured when the visual glitch occurred, as you can see the 0xE5 value is 0x00, which means the DSI83 did not register any interrupt error event.

     

    ams_trex_8mm:/ # dmesg | grep dsi83
    [  993.230778] sn65dsi83 3-002d: PLL has been unlocked
    ams_trex_8mm:/ # i2cdump -y -f 0x3 0x2d
         0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
    00: 35 38 49 53 44 20 20 20 01 00 81 18 00 01 00 00    58ISD   ?.??.?..
    10: 2e 00 16 00 00 00 00 00 12 00 03 00 00 00 00 00    ..?.....?.?.....
    20: 80 02 00 00 e0 01 00 00 21 00 00 00 1e 00 00 00    ??..??..!...?...
    30: 05 00 00 00 70 00 23 00 12 00 05 00 00 00 00 00    ?...p.#.?.?.....
    40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
    e0: 01 fd 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ??..............
    f0: 00 00 00 00 40 00 00 80 00 00 00 00 00 00 00 00    ....@..?........
    ams_trex_8mm:/ # i2cget -y -f 0x3 0x2d 0xe5
    0x00
    
    

    Understood, even though different voltage supplies might not be the root cause of the issue, is there any other part number such as the ds90cf363b which can work at 1.8v?

    You can find attached on this post a video of how the visual glitch looks like when it occurs, is there anything that you have observed before? It is important to note that it occurs sporadically (e.g., 1/100 times) and it is auto fixed when locking and unlocking the device LCD (i.e., reinitializing the video core of our board).

     DisplayPowerOnIssue.rar

    Any guidance will be highly appreciated,

    Thanks, and best regards,

    Esteban V.

  • Regarding another part that may work, try using the crossref tool: https://www.ti.com/cross-reference-search/singlepart?searchTerm=DS90CF363B

    The glitch is only on half the screen so this is most likely a sync issue. Can you enable the internal color bar pattern and see if the glitch still appears?

  • This will identify if the glitch is a result of the lvds output or the dsi signal going through

  • Hello Vishesh,

     

    Thank you for your quick response and for the suggestion of using the cross-reference toool.

    Regarding your questions, please find attached a new video, as it can be seen, when the issue occurs, if I send the DSI83 test pattern the issue isn’t there, and if I return to normal operation the issue occurs again.

     DisplayIssueTestPattern.rar

    Any guidance will be highly appreciated,

    Thanks, and best regards,

    Esteban V.

  • Hey Esteban, this means that issue is not the device itself, but the signal coming into the device. Please try using a ref clock to see if this fixes your issue.

  • Additionally, if using REFCLK isn't an option, try to reduce the distance between the DSI83 and the DSI signal generator. The issue is most likely due to random excessive jitter and signal integrity problems.