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  • Power Down Sequence Warning Explained

    There have been a number of questions asked about the danger of damaging the OLED and LCD displays by failing to observe the power down sequence detailed in the User Manuals. While it is understandable that during development and testing of projects and products, inadvertent loss of power may occur before an orderly shutdown of the display is possible. A relatively small number of these situations will usually not cause permanent damage to the display.

    The warning is in the documentation to impress upon the user, the need for a shutdown procedure prior to removal of power in order to extend the life of the display.

    All OLED and LCD manufacturers specify a power on and power down sequence similar to what is documented in the 4D Systems User Manuals for thier displays (see attached PDF files for example of manufacturer's datasheet functional specifications). Researching the datasheets for nearly any OLED or LCD display will reveal similar procedures and warnings.

    The fact is that these displays all require care in how they are powered up and powered down. The power up sequence is taken care of by the firmware that is imbedded in the display processor (PmmC), but there is no way for the firmware to detect or take action if power is removed before the screen voltage drivers are shut down.

    This fact is one reason why many portable devices that employ LCD or OLED screens either do not have removable batteries (iPod devices, for example) or warn the user to use the device's power down sequence before removing the battery (most cell phone/PDA/SmartPhone manufacturers).

    If you have questions regarding techniques that might be employed to reduce the the harmful effects of inadvertent shutdown, I would be glad to discuss it with you.

    Steve
    Attached files Univision_Tech_Datasheet_Cover.pdf (190.1 KB) Univision_Tech_Datasheet_Pg12.pdf (216.2 KB)
    Any technology, sufficiently developed, is indistinguishable from magic. A.C. Clark(RIP)

    NEW! Lower prices on all 4D Systems products for 2009 and continuing into 2010!
    http://shop.littlepcbsolutions.com

  • #2


    Hi Steve,
    I was wondeing if a reset before removing power would help, as I have only just got the display and envisage quite a while learning I am obviously concerned about damaging it.
    If this would help I considered a button across the collector and emitter of the reset transistor (I am using the MAX232 interface) so I can manually reset the display.

    Regards,
    Bobby

    Comment


    • #3


      RGV250,

      I think a reset would be kinder to the display, but the problem still remains that the display maker insists that the screen be "powered down", which is not the same as a reset.

      I see that you are using the uOLED-32028-P1T display. Try using the
      gfx_Set(CONTRAST, 0); command in your code to provide an opportunity to disconnect the display while the screen is effectively powered down. It won't help if the display just "hangs" while you're testing, but at least you will have a chance otherwise.

      I normally do something like the following at the end of my process to give myself a disconnect window:

      gfx_Set(CONTRAST, 0);
      pause(5000); // pause 5 seconds
      gfx_Set(CONTRAST, 5); // value 1 to 7 to power up the screen

      Steve
      Any technology, sufficiently developed, is indistinguishable from magic. A.C. Clark(RIP)

      NEW! Lower prices on all 4D Systems products for 2009 and continuing into 2010!
      http://shop.littlepcbsolutions.com

      Comment


      • #4


        Hi Steve,
        This may sound like a daft question but does the contrast command actually work or what should I see. (uOLED-32028-P1T)
        I have a touch cell which gives gfx_Set(9, 0); and then a 5 second delay as per your example below, the delay is working but I do not see any difference to the contrast, I would have expected to see quite a change for 0. I then tried a value of 6 but that did not look any different either.

        Regards,
        Bobby

        Comment


        • #5


          RGV250,

          There is a small problem with the mode 9 (Contrast) command in the current release. The new release, which should be available very soon, fixes the problem.

          Steve
          Any technology, sufficiently developed, is indistinguishable from magic. A.C. Clark(RIP)

          NEW! Lower prices on all 4D Systems products for 2009 and continuing into 2010!
          http://shop.littlepcbsolutions.com

          Comment


          • #6


            Thanks Steve,
            Just a thought but how about a section or a document on the forum for known bugs so that newbies like myself do not waste time thinking they have a problem with their code.

            Regards,
            Bobby

            Comment


            • #7


              New release Workshop Beta 2.1 is now available. This will also fix the contrast problem in the uOLED-320 modules.
              Atilla

              Comment


              • #8


                What about powering down uOLED 96 PROP? I cannot find any info on this??

                Hans

                Comment


                • #9


                  Hans,

                  If you look in the propeller Object Exchange (Obex) at the uOLED-96-PROP Object, you will see that it contains several Methods: PowerDown_Seq, PowerUp_Seq and Reset_OLED that can be called from you SPIN program.

                  Please read the comments associated with each Method so that you understand what each is for.

                  Steve
                  Any technology, sufficiently developed, is indistinguishable from magic. A.C. Clark(RIP)

                  NEW! Lower prices on all 4D Systems products for 2009 and continuing into 2010!
                  http://shop.littlepcbsolutions.com

                  Comment


                  • #10


                    Thanks! I should have looked better!

                    Comment


                    • #11


                      So, if I really follow the instructions, the demo program in fact is missing the PowerDown_Seq at the end. Shouldn't this be changed then? Running the demo and repeatedly powering down could really harm my unit...

                      Hans

                      Comment


                      • #12


                        If you intend to run the demo program repeatedly and you're concerned about damaging the screen electronics, then the obvious thing to do is modify the demo program to include the PowerDow_Seq method.

                        Steve
                        Any technology, sufficiently developed, is indistinguishable from magic. A.C. Clark(RIP)

                        NEW! Lower prices on all 4D Systems products for 2009 and continuing into 2010!
                        http://shop.littlepcbsolutions.com

                        Comment


                        • #13


                          Wouldn't it be a good idea to include a power down sequence in the 4DGL application, in the form of a button. Plus, perhaps, another one to 'power up'?

                          Comment


                          • #14


                            Dear Steve and other experts,
                            is setting the contrast to level 0 the same as power down? I can not find the 4DGL command for power down for my 96-G1 uOLED. Thanks for help.
                            Walter

                            Comment


                            • #15


                              Details of the gfx_Set() command can be found here:
                              http://www.4dsystems.com.au/developers/docs.php?cat=14&id=68

                              For the GOLDELOX displays (-GMD1 and -G1), setting the contrast to zero shuts the screen down. For PICASO displays (PMD2, PMD3 and P1), setting the contrast to zero, background color to black and clearing the screen before removing power is the safest practice.

                              Steve
                              Any technology, sufficiently developed, is indistinguishable from magic. A.C. Clark(RIP)

                              NEW! Lower prices on all 4D Systems products for 2009 and continuing into 2010!
                              http://shop.littlepcbsolutions.com

                              Comment

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