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Display, gen4-uLCD-70D, Serial COMM Not Working and Stuck into RESET

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  • Display, gen4-uLCD-70D, Serial COMM Not Working and Stuck into RESET

    I am working on a Project with gen4-uLCD-70D. From Last 2 Days Display is not Responding to Serial Communication. It does generate graphics from SD Card but not responding to Serial Commands. I have connected it with PC via gen4-PA for programming but Serial Port is RED. When I try to scan Port, Display goes into RESET and never comes back. Its ALL Blank. If I don't mount SD Card, Mounting Message flashes @ 1 Hz but COMM dosen't come alive. I have to disconnect power form Display and Re-Connect it to bring out of RESET State.

    I have tried by changing FFC Cable with another display's but NO Luck. Other Display does have Working COMM with same FFC Cable.

    As COMM is not working on Display my Project Controller can not update DATA on Display and I am Stuck. Around 10 to 15 Days it was working fine but from Last 2 Days it has problems.

    Please guide me through troubleshooting.

    I have buy this display recently. Can anybody tel me what is general Warranty Period for such Display from 4D.
    Click image for larger version

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    Click image for larger version

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    Attached Files

  • #2
    Hi Ravi,

    Have you always connected it that way? (PC ---uUSB Cable--> gen4-PA ---5 Way Cable----> gen4-IB ---FFC-----> Display)

    Could you please try to connect the Display directly to the gen4-PA via the gen4-PAs ZIF socket?

    Could you also try a different gen4-PA ?

    As for the warranty, you may refer to our terms and conditions page:

    4D Systems Terms and Condition.

    Best regards,


    • #3
      Yes I have developed my application in both way, with 5 way cable and with FFC directly connected to PA too. I have checked my problem with and without 5 way cable. Problem remains.
      I don't have another PA. But another display works with same PA. So there must be some problem with display itself. It does draw images but can not communicate. Is there any way to 're program display for disturbed communication? Thanks.


      • #4
        Hi Ravi,

        To be clear, your display is not blinking rapidly, right?

        It lights up and shows some images as it should but somehow it cannot be detected?

        Could you send a photo of your display's PCB?

        Best regards,


        • #5
          Display is NOT Blinking, nor Rapidly nor Slowly.

          YES. It lights up and Shown earlier programmed Images but NOT Communicating with HOST.

          Here is Photo of Display PCB.
          Click image for larger version

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          Click image for larger version

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          • #6
            Hi Ravi,

            Thanks for the clarification and sorry if I seem to be repeating myself.

            To ensure that the problem is not with the gen4-PA, please try the following.

            1. Connect your gen4-PA to your PC, please make sure that the display module (gen4-uLCD-70D) is not connected to the gen4-PA.

            2. Open your PC's Device manager.

            3. Look under the ports menu.
            3.a. If your gen4-PA is in a good condition, you should be able to see a Silicon Labs device similar to what's shown below
            Click image for larger version

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            3.b. If you don't see a silicon Labs device, this could mean that your gen4-PA or uUSB cable is broken.

            4. If your gen4-PA is being recognized as in step 3.a., please try cleaning the parts shown below to ensure that there are no shorting lines.

            You can do this by brushing over those areas with a toothbrush ensuring that no dust particle is causing one line to touch another.
            Click image for larger version

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            Best regards,


            • #7
              I have made some clean up for possible sorted Pins but NO Luck. PCB was already pretty much clean.

              I have suspected a strange Behavior. As shown above, when I connect my display First time it Turns ON. When I disconnect USB from My PC, it turns OFF. But when I Connect back USB, It doesn't turn ON. I have to remove 5 Way connection and then re-connect to turn it back ON. After all these, NO Communication at all.

              One more thing, I have made some continuity test on communication lines and I found RX and GND Sorted. TX has no sort with anything. RESET is pull up to 3.3v. What do you think of such problem? Is it the failing of DIABLO16 processor? How can I fix it. I am looking more into PCB for reason to sort but any suggestions are welcome.


              Is there any way to know that DIABLO16 processor is still working properly or Not? Is it possible to replace DIABLO Processor in case of problem is because of it?
              Last edited by RaviPatel; 29 May 2019, 11:40 PM.


              • #8
                Hi Ravi,

                Sorry for the delay.

                As you may know, our forum site has been offline for a while.

                You said that the Rx was shorted to ground. I think that might be causing the issue, have you found what's causing the connection?

                Could you disconnect the gen4-PA from the PC and the display then check if Rx and ground are still connected?

                If they are, it would mean that your gen4-PA is defective and you might need to buy a new one.

                However, since you said that you've succesfully used it for other devices, I think that's highly unlikely.

                Keep me updated if you have found ground and rx ar connecting.

                Best regards


                • #9
                  Yes you are right that gen4-PA is not defective. Sort is coming from LCD PCB Itself. On PCB RX is directly connected to DIABLO 16 Pin. Only a Resistor is connected between RX Track and one more track that goes into Power Regulator IC. So there could be chance of something wrong with Regulator or with DIABLO 16 Processor.

                  Is there any way to confirm DIABLO 16 Processor is OK and Working? I think it is not Working. If I Buy a new DIABLO 16 Processor from Mouser USA and replace older one with this new one on PCB, could it work? Do I need to Program DIABLO 16 or it is pre-programmed with software?

                  Anyway we are ordering new LCD to supply our client.


                  • #10

                    Based on the datasheet, the ground pin and the Rx pin on the Diablo16 chip are very close to each other, I would think that that is what's causing the short.

                    Click image for larger version

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                    The quality of your previous photos are a bit low, would you like to send clearer photos?

                    As you may know, the FFC Cable is prone to wear out after some time of usage, to ensure that this is not causing the defect, please check that the FFC cable is in good condition as shown below.

                    Click image for larger version

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                    If I Buy a new DIABLO 16 Processor from Mouser USA and replace the older one with this new one on PCB, could it work?
                    That could work, however, removing the old processor and replacing it with a new one could be difficult.

                    Aside from that, we're not yet sure if the Diablo16 chip is really broken.

                    To check if Crystal X1 is working properly, could you check if the voltage across it is roughly 1.3 V?

                    Best regards,