Techniques for drawing "snow" static on TFT without tearing?

Other Hardware Displays
21

Hi all, I downloaded Bodmer's sketch and ran it on an ESP32-WROOM-32 driving a 320*480 ILI9341 TFT.
Noise is too fast form my phone's camera to catch!
Only modification to get full screen on my display: in setup: tft.setAddrWindow(0, 0, 320, 240);
tft.setRotation is (1);

here is a picture from the workbench - photoncatcher

https://thesolaruniverse.files.wordpress.com/2021/03/bodmer_noise_esp32.png(image larger than 4 MB)

22

Because it is just a random pixel stream the "for loop count" is only important for the frame rate measurement. The sketch sends bursts of 32 pixels so for a display with width W and height H in pixels the line would be:

...
    for (uint16_t cnt = (W * H)/32; cnt; cnt--) {
...

At 40MHz SPI rate this gives about 30fps for a 320x240 display (32.55fps is theoretical maximum at 40MHz SPI clock with no loop delays).

23

I though I would try the "noise" test on a Raspberry Pi Pico.

128 x 128 noise with the SPI clock rate at 62.5MHz (close to the maximum "overclocking" for the ILI9341), the result is 174 fps. 320 x 240 figure is 37fps. This is just using one of the 2 processor cores.

Very good for a processor which is advertised at $4.

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