The yeild() is a function to relinquish the CPU to make another task to use CPU. But in case of Arduino Uno, it dose nothing.
The yield() is defined in hardware/arduino/avr/cores/arduino/hooks.c as below.
The yield() is defined as __empty() and the __empty() dose nothing.
The attribute is specified as weak, a user can redefine this function.
June 19, 2020