Demonstration of chaining 4 times, that activate one another in different ways.

Clock: 216MHz; 25MHz external oscillator with PLL.
LED on PI1.
PB4, PI0 and PB15 (Disco board's ARD D3, D5, D11 respectively)

This project is a proof of concept (that I can).

Might be useful for someone who wants to figure out how the stuff works. I commented almost every line to make it simple to understand.

Hardware:
STM32F746 Disco board

Software:
STM32CubeIDE
No libraries used except for CMSIS register definitions.