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Using LCD in graphic mode - persistency issue?? — Parallax Forums

Using LCD in graphic mode - persistency issue??

vaclav_salvaclav_sal Posts: 451
edited 2011-05-13 12:56 in General Discussion
I am looking into building an analog type meter display using LCD similar to one advertized at SparkFun. (http://www.sparkfun.com/products/710 – link provided for technical reasons, not an advertizement)

I have never used LCD which required relatively rapid update and
I am wondering if this type of LCD has a “persistence” issue caused
by the display technology itself or by the controller speed of updating the display.
Would the processor itself have an noticeable effect too? ( SEROUT speed)
I 'll be using BS2e.

For example if my analog meter “needle” travels from zero to full scale in one second would I see a smudge of pixels or nice needle skipping pixels?

Please reply only if you have an actual experience updating LCD in this fashion.
I am not soliciting opinions this time.

Thanks for reading and understanding.
Vaclav

Comments

  • Erik FriesenErik Friesen Posts: 1,071
    edited 2011-05-12 14:59
    It may depend some on the driver chip, whether or not its an off brand. I really think your limitation with be the bs2, not the screen. A complete screen change takes feeding it 1024+ bytes.
  • max72max72 Posts: 1,155
    edited 2011-05-12 22:16
    On the product page someone posted sample videos.
    It could give you an idea.
    Anyway moving a needle full scale either require a lot of refreshes or selectively clearing/setting the pixels.
    My guess is you will have problems to get this update speed.
    Probably a propeller and one of Ray's LCDs would get you closer.
    Massimo
  • vaclav_salvaclav_sal Posts: 451
    edited 2011-05-13 10:20
    Erik,
    I think in case of a "needle" I should be able to delete the old position and write the new one.
    But then I will run out of variable space for sure unless I can figure out how to do LINE in PBASIC.

    I think you were thinking doing it Windoze style where it is easier to rewrite the whole sceen.
    Either way, thanks for reply.
    Massimo
    I am sure Prop would work better. I am not set hard on BS2e it it won't do the job.
    Thanks
    Vaclav
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2011-05-13 12:56
    No, I just know how those screens pixels are arranged, and calculating everything is going to take some time and cycles. The propeller will do it easily, plus there is code in the exchange to use the ks0108.
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