this post was submitted on 26 Jun 2025
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Is SPI just "slow"? (feddit.org)
submitted 1 month ago* (last edited 2 weeks ago) by bvoigtlaender@feddit.org to c/askelectronics@discuss.tchncs.de
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Hi, hope this post is fine in regard of rule 2.

Currently doing some fun stuff with an Arduino and have it hooked up to an 128x160px and communicate with it over SPI. If i color in all 20480 pixels it takes about 2 seconds to be done and i can watch the rows change one after another.

I was wondering if there are some tricks to speed this process up a bit or does it really just come down to minimizing the pixels to be changed?

The module im using is this one: https://www.waveshare.com/wiki/1.8inch_LCD_Module

Here is also my current code if anybody cares to take a look, even though i just rewrote the example code more or less so i would understand it. https://codeberg.org/bvoigtlaender/open-phone/src/branch/main

EDIT: Thanks to jeinzi, nickwitha_k and cmnybo I have managed to bring the rendering time down from 2142ms to 80ms

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[โ€“] jeinzi@discuss.tchncs.de 10 points 1 month ago (1 children)

I noticed that you use digitalWrite multiple times for each transmitted pixel. That function is pretty slow - you should instead manipulate the microcontrollers registers directly for maximum performance. If you are using an Arduino, this article will help: https://roboticsbackend.com/arduino-fast-digitalwrite/

[โ€“] bvoigtlaender@feddit.org 3 points 1 month ago

Thank you for the article it is really interesting. Always assumed it would already do just that but it does make sense considering the amount of Controller it has to support. Will be changing that anywhere it gets called often.