如何全局#define 预处理器变量? [英] How to globally #define a preprocessor variable?

问题描述

我正在用 C++ 编写 Arduino 草图.我希望用户能够直接在sketch.ino 文件中#define一个常量，这将需要编译代码.Arduino IDE 使用 g++ 编译器.

I'm programming an Arduino sketch in C++. I want the user to be able to #definea constant directly in the sketch.ino file which will be needed to compile the code. The Arduino IDE uses a g++ compiler.

假设我们有三个文件:

sketch.ino
sketch.h
sketch.cpp

在sketch.h中我定义了

In sketch.h I defined

#define OPTION_1 0
#define OPTION_2 1
#define OPTION_3 2
#define OPTION_4 3
#define SLOW 0
#define FAST 1

在sketch.ino中，用户定义MYOPTION:

In sketch.ino the user then defines MYOPTION:

#define MYOPTION OPTION_2

在 Sketch.h 中，我使用变量来定义宏:

In sketch.h I use the variable to define macros:

#if MYOPTION == OPTION_1 | MYOPTION == OPTION_2
    #define SPEED FAST
#else
    #define SPEED SLOW
#endif

在 Sketch.cpp 中，我用它来改进时间关键代码:

In sketch.cpp I use it to improve time critical code:

MyClass::foo() {
    // do something
    #if SPEED == FAST
    // do more
    #if MYOPTION == OPTION_2
    // do something extra
    #endif
    #endif
    #if MYOPTION == OPTION_4
    // do something else
    #endif
    }

不幸的是，在 Sketch.cpp 中似乎无法识别 MYOPTION 的定义.然而，sketch.cpp 确实识别了sketch.h 中定义的变量.有没有办法全局定义预处理器变量，以便可以在使用它们的任何文件中访问它们?

Unfortunately the definition of MYOPTION doesn't seem to be recognized inside sketch.cpp. Hower sketch.cpp does recognize variables defined in sketch.h. Is there a way to define preprocessor variables globally, so they can be accessed in any file that uses them?

推荐答案

• 将选项定义移动到单独的文件中，例如选项.h.如果您愿意，也可以在 Sketch.ino 中定义它们.
• 在sketch.ino 和sketch.h 中包含options.h.
• 将所有依赖于 MYOPTION 宏的代码从 Sketch.cpp 移动到 Sketch.h.
• 在包含sketch.h之前在sketch.ino中定义MYOPTION:
• Move the option definitions to a separate file, e.g. options.h. You could also define them in sketch.ino if you like.
• Include options.h in sketch.ino and sketch.h.
• Move all the code that relies on the MYOPTION macro from sketch.cpp to sketch.h.
• Define MYOPTION in sketch.ino before including sketch.h:

#include "options.h"
#define MYOPTION OPTION_2
#include "sketch.h"

以下是使用此技术的流行库的示例:

Here's an example of a popular library that uses this technique:

https://github.com/PaulStoffregen/Encoder

它允许用户通过 ENCODER_DO_NOT_USE_INTERRUPTS 和 ENCODER_OPTIMIZE_INTERRUPTS 宏从草图中配置中断的使用.

It allows the user to configure the use of interrupts from the sketch via the ENCODER_DO_NOT_USE_INTERRUPTS and ENCODER_OPTIMIZE_INTERRUPTS macros.

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