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Author Topic: fading screen flicker  (Read 128 times)


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fading screen flicker
« on: October 05, 2019, 04:54:26 PM »

on a 800*480 display, driven by BT815, I made a background image and 20 icons of 100x100 pixels. All images are converted to 8x8 ASTC and reside in flash.

When this screen activates, all images are show up OK, but the screen flickers quite annoyingly. This slowly disappears: after about 15 seconds the screen is stable and I can switch between screens without any flicker.

If I start the display without the icons, but just the background, it shows up almost stable, but activating the icons in the first 15 seconds causes visible fading flicker. Using less compression for the background, and so more data, makes the flicker heavier and longer.

I just cannot grasp what is wrong with it. If the graphic engine is overloaded, how come the flicker disappears? Anyone any ideas?

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Re: fading screen flicker
« Reply #1 on: October 07, 2019, 03:01:23 PM »


Can you let me know what display settings you are using?
Aslo are you using a custom hardware design?

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Re: fading screen flicker
« Reply #2 on: October 09, 2019, 10:49:50 PM »

I was intrigued by this.
So I converted 30 icons to 100x100 and put them as ASTC into a flash image.
Code: [Select]
unified.blob                                   : 0     : 4096
88_1_104x104_COMPRESSED_RGBA_ASTC_8x8_KHR.raw  : 4096  : 2752
88_104x104_COMPRESSED_RGBA_ASTC_8x8_KHR.raw    : 6848  : 2752
89_1_104x104_COMPRESSED_RGBA_ASTC_8x8_KHR.raw  : 9600  : 2752
89_2_104x104_COMPRESSED_RGBA_ASTC_8x8_KHR.raw  : 12352 : 2752

This is rather small, only 85kB in total.

Then I created a simple test-code included lines like this:
Code: [Select]
EVE_cmd_setbitmap(0x800000 | ((4096+(2752*4))/32), EVE_COMPRESSED_RGBA_ASTC_8x8_KHR, 100, 100);
EVE_cmd_dl(VERTEX2F(0, 10));
EVE_cmd_setbitmap(0x800000 | ((4096+(2752*5))/32), EVE_COMPRESSED_RGBA_ASTC_8x8_KHR, 100, 100);
EVE_cmd_dl(VERTEX2F(105, 10));
EVE_cmd_setbitmap(0x800000 | ((4096+(2752*4))/32), EVE_COMPRESSED_RGBA_ASTC_8x8_KHR, 100, 100);
EVE_cmd_dl(VERTEX2F(210, 10));
EVE_cmd_setbitmap(0x800000 | ((4096+(2752*4))/32), EVE_COMPRESSED_RGBA_ASTC_8x8_KHR, 100, 100);
EVE_cmd_dl(VERTEX2F(315, 10));

I can setup any of the 30 icons to be displayed and I am displaying 28 Icons in total right now plus a small monochrome image from RAM_G.
The display-list size is 1252 bytes, bytes send by SPI are 676, refresh is 20ms.
The display is a PAF90 from Panasys with a BT815 which is clocked 72MHz, the flash is a W25Q128JVSIQ.

Now here is the problem, when I display more than eight *different* icons, it starts to bug out.
The first thing that happens with one additional icon is that the display is not properly build anymore.
It kind of resets after the third row, repeating at the bottom what should be on top.
And make the refresh time longer does not help.
Adding annother icon and the colors in that repeated frame at the bottom gets messed up.
Now I added two more and it flickers like crazy displaying only the first row on the top and a portion of it at the bottom.

Going back to only eight different icons for the 28 icons displayed, everything is fine again.

It looks like there either is a bandwidth issue with the BT815 or the image decoder trips and resets or both.
If necessary I can provide pictures but this should be easily reproduceable.

Edit: I played with the code and took a couple of images.

These all use the same code but while the first (20191013_203941s.jpg) is displayed okay,
the display for the other three is messed up.
The only difference between these images is the amount of different icons to be displayed.
« Last Edit: October 13, 2019, 07:59:20 PM by Rudolph »


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Re: fading screen flicker
« Reply #3 on: Today at 10:39:58 AM »

I think rendering the image from RAM_G, instead of flash, shall be helpful.
You can use cmd_flashread to copy the ASTC data into RAM_G.