I haven't used an STM32 before and I want to learn how to use them. It's been a few years since I've designed a piece of hardware and I want to learn how to use KiCAD. I have never made a Pi hat and I want to figure out how to. I don't know how these LED matrix displays work and I want to figure it out. That's what I would claim as the reason I decided to make my own LED matrix controller. This introduces a risk I can't accept: that the night before shipping a huge order to a giant customer I find out the controller doesn't do what I want, and there's nothing I can do to fix it. The documentation for the controllers is as hard to find as documentation for the display. The manufacturers of displays usually recommend or supply a controller you can buy that does almost what I want, almost.

I know there are such things as LED matrix display controllers. What I want is a display controller that I can set and forget or draw 'images' to, without having to worry about real time signal generation or clocks or strobes or addresses or PWM or BCM or any of the other things that need to be handled to control one of these displays. They require constant refreshing and this takes a lot of processing power which you might want for other things like pinging a server and retrieving some data to show. There's not a lot of documentation available about how to drive them. Big LED matrix displays are a much better choice for a display with real impact. When you need something big and bright and bold then character LCD displays are not a good choice. They are simple to use, easy to find and great for a simple, small UI. I've been using character LCD displays in projects for a long time. Graphical mode will allow you to create static or moving images on the display.

In graphical mode the Raspberry Pi provides an array of RGB data. In this mode the Raspberry Pi calls printf style functions with strings of text to write to a display. These modes are used to classify the display. The goal of this project is to make a Pi HAT for LED Matrix displays that supports the HUB08 and HUB75 interface and can drive displays in character or graphical modes.

Stm32 blue pill schematic clock