Code snippets to be used on the ATMega328P microcontroller.
No libraries are used, bare-metal C code.
The Arduino Nano is a very cheap board and a really good way to learn more about embedded systems, I broke a few of them while experimenting.
The datasheet is the best resource to learn about the details of the microcontroller.
Data sheet: http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-42735-8-bit-AVR-Microcontroller-ATmega328-328P_Datasheet.pdf
Pinout: https://components101.com/microcontrollers/arduino-nano