.fail
Generates an error or a warning. If the value of the expression is 500 or more, as will print a warning message. If the value is less than 500, as will print an error message. The message will include the value of expression. This can occasionally be useful inside complex nested macros or conditional assembly.
The text of the Arduino reference is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.