Timer/Counter

http://arduino.vn/bai-viet/411-timercounter-tren-avrarduino

http://www.hocavr.com/2018/06/c-cho-avr.html

https://www.digikey.com/en/maker/blogs/2022/how-to-avoid-using-the-delay-function-in-arduino-sketches

https://www.hobbytronics.co.uk/arduino-timer-interrupts