ESP32-HUB75-MatrixPanel-DMA/fillrate.md

Estimating fillrate

Here are some results of simple tests on filling DMA buffer with data. Filling DMA buffer requres lot's of memory operations on a bit level rather than doing simple byte/word wide store and copy. And it looks like it's quite a task both for esp32 core and compiler. I've done this while optimizing loops and bit logic along with testing compiler results.

So the testbed is:

• Matrix modules: 4 x FM6126A based 64x64 modules chained in 256x64

A simple sketch:

• allocating single DMA buffs for 256x64
• allocating (NUM_LEDS*3) bytes for CRGB buffer
• measuring microseconds for the following calls:
  • clearScreen() - full blanking
  • fillScreenRGB888() with monochrome/gray colors
  • filling some gradient into CRGB buff
  • painting CRGB buff into DMA buff with looped drawPixelRGB888()

Pattern	Reference	Ref+SPEED	Optimized	Optimized+SPEED
fillScreenRGB888()	14570	14570	13400 (8.5% faster)	5520 (164% faster)
CRGB buff fill	760	760	760	760
updateMatrixDMABuffer(CRGB)	7700	32080	55780 (38% faster)	33500(+4.2% slower)

to be continued...