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  • Display flashes at start-up

    When the controller is powered up, the display can be seen flashing shortly, presumably due to some activity during initialization.
    Is there a way to prevent this? Disabling back light or whatever?

    Thanks in advance,
    MIchael

  • #2
    Hi Michael

    The flashing you see at startup is caused by your PC initializing the programming adaptor/cable's IC, the FTDI or Silicon Labs chip on the programming cable/adaptor. If the cable is plugged into your PC first, so it appears as a USB device, and then you plug it into the display, this shouldn't happen. Likewise, if you power the display module directly from a 5V supply, rather than from your PC, then it also should not happen.

    What display module are you using by the way, you haven't mentioned.

    That said above, there are a few models which might flash (depends what you class as a flash though) on startup, due to the way the display itself is initialised. Let me know what display you are talking about so I can be more specific.

    I hope that helps

    Regards
    James

    Comment


    • #3
      Hi James,

      thank you for your reply. I'm using a ULCD-24PTU display module. I suspected the USB, too. Great minds think alike, don't they?
      But unfortunately this is not the case. I have two modules: a factory-programmed one, and another with my own code. Upon connecting the the 5-way cable, they both flash.
      To be sure, the programming adapter have been connected to the PC for long enough to get initialized before powering the display module.

      Comment


      • #4
        OK, that helps narrow it down. Just checked a 24PTU and yes, their is a flash at power up that can't easily be explained.

        We'll have a look at it in the next day or two and see if something can be done.
        Mark

        Comment


        • #5
          OK, thank you.

          Comment


          • #6
            Hi Mark,

            have you found a solution?

            I tried the pin_LO(BACKLITE) function as the first instruction in the main() function, and the pin_HI(BACKLITE) function after initialization. These functions work correctly, but the problem is still there. I think this pair of functions should be inserted into your firmware. What do you say?

            Comment


            • #7
              Oops, thanks for the reminder, we had almost that task complete and were trying to look at the 'bigger picture'.

              I'll email you a PmmC to try in a few minutes
              Mark

              Comment


              • #8
                Hi Mark,

                thank you. I got the file. I'll try it later today, and let you know of course.

                Comment


                • #9
                  Mark,

                  I have tried it. The LCD still flashes (although in a somewhat "better" way - a smeared large spot rather than a sharp rectangle, and it is not so bright as before).
                  To be sure - I disabled the backlight in the beginning of the main() function, and did not enable it at all. Nevertheless, the LCD flashes when I connect the +5V power supply.

                  Comment


                  • #10
                    That, as far as I can see, is the best that can be done.

                    Actually, I'm not even sure if it flashes anymore, or if it's just my eyes adjusting from the off to the on state.
                    Mark

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                    • #11
                      "just my eyes adjusting from the off to the on state."

                      That's why I did the experiment - the first instruction in my main() function was pin_LO(BACKLITE), and I never enabled the backlight.
                      It still flashes,but, like I said, in a somewhat better manner.

                      Comment


                      • #12
                        The backlight is turned on 'long' before main is reached.

                        The display is initialised, it waits 50ms for all the pixels to become 'active', the screen is cleared, i.e. all pixels are turned on (to make black), then the backlight is turned on.
                        Mark

                        Comment


                        • #13
                          OK, got it.

                          Now I have noticed that I need a stronger press on the touchscreen to activate an on-screen button. Is that a normal behavior after re-loading the firmware? Do I just have to re-calibrate the touchscreen?

                          Comment


                          • #14
                            For a the PTU displays you need to redo touch calibration after loading a new PmmC
                            Mark

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                            • #15
                              OK, thank you.

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