Follow me down the optimization rabbit hole

Intro The ESP32 (there are now quite a few varieties), is an incredibly versatile microcontroller. It's main value proposition has always been that it's a low cost MCU with WiFi capability - something that was relatively unique when it was first released. The processing speed and internal RAM size prevent it from doing tasks that Linux machines like the Raspberry Pi series can do, but there is some overlap where the ESP32 can still surprise you with its abilities. I've been working on projects which use a variety of ESP32s as video and animation playback devices. I recently released an optimized MPEG-1 player ( https://github.com/bitbank2/pl_mpeg ) and was looking at other applications for video playback. Until now, I've seen multiple projects which have been using my JPEGDEC jpeg decoder library to play motion-jpeg videos. I was curious to see if anyone had published a project to play motion-jpeg streams from public IP camera URLs. I didn't find any, so I thought ...

I've been wanting to create a series of lessons on code optimization and something I encountered yesterday seemed like a good starting point. There are many ways to get the same results in software; not all are efficient. Optimizing code is one of those skills that any programmer can do, it just takes a little extra experience and patience. In this lesson I'll walk you through the thought process of how I analyze code followed by the steps to improve it. I will attempt to show you how code looks "through my eyes". We're going to look at part of the font rendering code within LVGL. By optimizing this code, I'm not intending this lesson to be a criticism of that project, it's just a good example of code I analyze. Here's the code in question: ( LVGL Github link ) The purpose of this type of optimization is to improve the C code for all target systems, not to slice 1 clock cycle off of register reads. A 'normal' C programmer will look at this code...