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  • µVGA-II Serial Slow Speed Issues

    I have got a serial VGA-II connected to an Arduino and as an output connected to a 7" LCD.

    When I try and show a image from the SD card on the module the actual rate of the image showing on the is very slow. Is this normal?

    My baud rate is 38400 bps.

    You can see what I mean in this clip:


    Thanks.

  • #2


    You haven't said what resolution you have the display set at and what commands you are using to get the display to display that way.

    If you were attempting to play a video at 800x480 off a uSD in RAW format, you would get just over 1 fps.

    So one image at a time from FAT, with an erase would probably be about that speed.
    Mark

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    • #3


      Resolution is 800x480 pixels.

      I use the "4DGL, SGC Picaso - GCI -Fat Selected Folder" to produce the files to then copy to the uSD card.

      Can it not be made faster?

      Comment


      • #4


        Lower the resolution, or use RAW.

        Consider what you are writing to the display and the need to do it.

        The bottleneck is the the speed the uSD card can be read in SPI mode, it's pretty fast, but once you start using large screens it's got a lot of work to do.
        Mark

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        • #5


          If I lower the resolution, then the images that appear on the screen are not full screen. They appear in the middle.

          What do you mean by reading the uSD card as SPI?

          I've tried RAW mode and speed doesn't change.

          Thanks.

          Comment


          • #6


            Try a different monitor, some brands will do the right thing and expand the size screen. Check the monitor's adjustments as well.

            SPI mode is a single wire interface to uSD and SD cards. It is most commonly used by small systems. uSD and SD cards can also be accessed in SD mode, this mode uses 4 wires and license fees need to be paid to the SD association before it can be used.

            What are you trying to achieve?

            What commands are you sending?
            Mark

            Comment


            • #7


              I've tried many monitors/LCDs and results are pretty much the same.

              I am not sure how to achieve what's supposed to be achieved with SPI or SD mode.

              We're trying to make an interactive systems on a 7" LCD, but needs to load photos much quicker!

              I am using the library from here:http://embeddedcomputing.weebly.com/serial-lcd.html

              Thanks.

              Comment


              • #8


                Hmm, RAW mode is much faster, I got these results

                Size FAT RAW
                800x480 1.50 0.44
                640x480 1.19 0.34
                320x240 0.32 0.11

                For FAT the speed will vary a bit, depend on the uSD's cluster size and file fragmentation.

                You can also make the images only use part of the screen and leave something else on the rest of the screen.

                In 320x240 mode you can also write to one page whilst display another and then flipping.
                Mark

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