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Distorted image on GEN4 4DCAPE 50CT CLB with BeagleBone Black Wireless

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  • Distorted image on GEN4 4DCAPE 50CT CLB with BeagleBone Black Wireless

    Hi.
    I just bought GEN4 4DCAPE 50CT CLB and I want to use it with brand new BBBW.
    When I connect the cape and the display using the flex cable and boot Debian 9.9 (or 9.11), everything seems to be working except one annoying detail - the image is distorted.

    It seems like some of the lines are shifted few pixels to the left making text on the display indecipherable.

    It is obviously some interference from the outside, because when I touch the flex cable with my fingers, the distortion gets worse. I created short video to demonstrate the issue:
    https://youtu.be/qKLuBbnGtnI

    Is this normal? Am I making some rookie mistake?

    I am new to 4D capes and to BeagleBone, but have many years of experience with RaspberryPi.

    Thank you very much for any suggestions.
    Regards
    Jan
    Last edited by jeza08; 14 January 2020, 07:27 PM.

  • #2
    Hi Jan,

    Welcome to the forum!

    Thank you for the video you attached.
    Can you check if the FFC cable is properly latched on both ends (Display and Adaptor Board)?

    Please let us know.

    Best Regards,
    Kevin

    Comment


    • #3
      Hi Kevin.
      Yes, it is. That was the first thing I checked. I released the latches on both sides, disconnected the cable completely, carefully inserted the cable back in on both sides (the blue side facing the board on each end) and locked the latches again. I don't think the connection could be any better.

      I thought there could be some interference with the boards WIFI module, but this was not confirmed. I disabled the WIFI using:
      sudo connmanctl
      disable wifi

      No change. The image is still distorted...

      Best regards
      Jan

      Comment


      • #4
        Hi Jan,

        Thank you for your reply.

        Could you open a support ticket here: https://4dsystems.com.au/contact/, so we can verify some information in your display.

        Best Regards,
        Kevin

        Comment


        • #5
          Hi Kevin.
          Thanks for the suggestion. I submitted the ticket here:
          (URL Deleted)

          Regards
          Jan

          Comment


          • #6
            Dear 4D team,

            I have exactly the same problem as jeza08: distorted display image on 4DCAPE 50CT CLB with BeagleBone Black Wireless (debian 9.x). Flex cable seems ok. All parts are brand new.

            Question: What was the resolution of jeza08's problem, please ?

            Regards,
            Marco

            Comment


            • #7
              Dear Marco,

              Good Day.

              Welcome to the forum.
              It has the same as your display resolution. Can you provide images of your BBBW (Top and Bottom) for us to check if you have the same version of jeza08's BBBW?

              Thank you.

              Best Regards,
              Ferdinand

              Comment


              • #8
                Dear Ferdinand,

                please find attached images of my HW components (BBBW and 4DCAPE) as well as a display screenshot showing the distortion.
                The distortion appears to be worse on the right side of display.

                I purchased both components (BBBW and 4DCAPE) one week ago from Farnell/element14 distributor.

                Best regards,
                Marco
                Attached Files

                Comment


                • #9
                  Dear Marco,

                  Good Day.

                  Thank you for the images and additional information.

                  We also have that kind of BBBW that you have which also notices that distortion on the right side of the display. But using the same display with all its peripherals with the other version of the BBBW, in which we haven't noticed any distortion at all. This seems to be strange and only knows that the display module is properly working.

                  You can check the link that shows that it is working on that version of BBBW.
                  BBBW Test

                  I hope this helps.

                  Best Regards,
                  Ferdinand

                  Comment


                  • #10
                    Dear Ferdinand,

                    thanks for the link with the videos.

                    I would have 2 further questions, please :

                    a) Do you know if the distortion issue does also exist on that version of BBBW with the 4DCAPE-50T display (resisitive touch) ?
                    b) Did you see any design changes between both BBBW versions ? (in terms of PCB layout)

                    I will try to find out where this signal jitter is coming from. I guess, this will help 4DSystems too.
                    Any help or hint is appreciated.

                    Best regards,
                    Marco

                    Comment


                    • #11
                      Dear 4D Team,

                      I did some oscilloscope measurements for technical comparison. Could your HW engineers have a look into this, please ?

                      Picture1 is showing the BBBW connected to a competitor 5" capacitive display. In the background you can see the measured LCD_PCLK signal (P8_28). The display picture is not distorted and the PCLK signal quality is ok (a bit less than on a BBB but still inside the tolerances)

                      Picture2 is showing the same BBBW connected to the 4DCAPE. The PCLK signal quality gets absolutely borderline, I would say its out of spec.

                      So, for me this looks like the problem is more located on the 4DCAPE side.
                      I guess, with the previous BBBW revision the PCLK signal quality got a bit reduced, but is still within the limits and hence the issue is not visible. With the current BBBW revision it's getting out of tolerance and hence causing the distortion.

                      Click image for larger version

Name:	SEED-5CAP-Ok.JPG
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Size:	1.21 MB
ID:	71928Click image for larger version

Name:	4DCAPE-50CT-Distorted.JPG
Views:	51
Size:	1.28 MB
ID:	71929
                      Best regards,
                      Marco
                      Last edited by bmjp146; 29 April 2020, 09:34 PM.

                      Comment


                      • #12
                        Hi Marco.
                        Great analysis. I didn't have time to look at the signals in lab myself, so I am really grateful someone else is involved as well.

                        I have however compared the schematics of BBB (version A3) and BBBW (version A5). There is one difference that might be relevant to our issue. The HDMI interface is supplied from net HDMI_1V8 which is connected to VDD_1V8 through ferrite bead. The types of the ferrite bead differ between the two versions. See attachments.

                        Best regards
                        Jan
                        Attached Files

                        Comment

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