Electrical – use C++ stl in avr-gcc

There are many benefits to inline functions over preprocessor macros:

• Type checking. The compiler will complain if the arguments are of incorrect type.

• No risk of multiple evaluation: macros can be dangerous when the argument is an expression, consider:

  #include <stdio.h>
  #define square(n) ((n)*(n))
  
  int main(void)
  {
      int x, i = 0;
      while (i < 10) {
          x = square(i++);
          printf("%d\r\n", x);
      }
      return 0;
  }
  

• Can include multiple lines of code without trailing backlashes.
• Inline functions have their own scope for variables and they can return a value.

Macros can be useful e.g. when concatenating tokens into code, so as to simplify some complex declarations.

Consider macros as just a dumb text replacement functionality. A good rule of thumb is to avoid function-like macros, unless there is no other viable solution.

It is a common misconception that inlining always equals faster code. Keep in mind, that every inlined call from more than one place adds up to code size. Premature optimization is not a virtue, even when working with the constrained resources of a microcontroller.

GCC interprets the inline keyword as a mere hint. There is no guarantee thet the function will actually be inlined. To have GCC inline your function regardless of optimization level, declare the function with the always_inline attribute:

void function() __attribute__((always_inline));

Debouncing is something you must be familiar with when using buttons. When a contact closes, it does not just close, but bounces back a few times until it finally settles in its closed position.

Depending on how fast your sampling code is, the code can count many button presses, although you only moved your finger once. There are a number of debouncing strategies around. Search www.avrfreaks.net for debouncing and you will find plenty of posts. Most of the recent threads contain a link to some pretty good old examples/strategies which you can use.

This might not be the only problem with your code - but we can only know that when we've seen the code. Post it here or on avrfreaks and we might be able to help you.