Hey, I couldn't get an answer in the adafruit forum, but maybe somebody can help here:
I try to figure out the maximum SCK frequency for a robust SPI communication between an Arduino Uno R4 and my Adafruit 1770 display using ILI9341 driver. While the library Adafruit_ILI9341 offers frequencies of 24MHz and above, I found a SCL serial clock period timing of 100ns (min) in the ILI9341 datasheet, which would limit the frequency to 10MHz (max). Did I mix up something or what did I miss?
#ILI9341 maximum SPI clock frequency
bitter otter
sly mirage
I’ve been able to push similar displays faster than their datasheet recommends. Their timing minimums try to guarantee performance, so that 10MHz is a good starting point for a “robust” spi communication. However, datasheets are ultimately a guideline, as in my testing I’ve driven a similar ili9342c display at up to 26MHz without much issue.
I will say that if your framerate is good enough, don’t try to go too crazy with SPI speed. Looking at it with an oscilloscope, sometimes I wonder how it still works at those speeds.
bitter otter
Hem, thanks for your answer. I had looked more closely into the datasheet, as I had issues at 24MHz and even some few failures at 16MHz. It helped to shorten the wires between MC and display down to approx. 80mm (they were unreasonably long as it was a prototype setup). Looking at the signals with my oscilloscope, they looked quite weird, therefore I limited the SPI CLK to 8MHz, but that lookes quite slow (even on a 320 x 240 display). Was just wondering why Adafruit sets the frequency so high in their ILI9341 library ...