如何在C++中使用预处理器指令的帮助下在语句之间插入语句？

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我试图通过非常快速地打开和关闭LED来编程一个Arduino由于PWM LED矩阵。为了控制亮度，我想在LED的开启和关闭状态之间添加额外的指令。亮度应该由预处理器变量设置。 Arduino拥有84MHz Cortex-M3 ARM处理器。如何在C++中使用预处理器指令的帮助下在语句之间插入语句？

这是我的代码目前以何种方式提高亮度的简化：

uint8_t volatile dummy = 0; 
uint8_t i; 

for (i=0;i<1<<current_layer;i++) { // every next layer has double the amount of pulses 
    LED_STATE = ON; // several pulses in one go speeds up the for loop 
    dummy = 0; // increases ON-time 
    LED_STATE = OFF; 
    LED_STATE = ON; 
    dummy = 0; 
    LED_STATE = OFF; 
    LED_STATE = ON; 
    dummy = 0; 
    LED_STATE = OFF; 
    LED_STATE = ON; 
    dummy = 0; 
    LED_STATE = OFF; 
}

现在我希望能够根据处理器变量像这样可以提高亮度：

#define BRIGHTNESS 2 
// inside loop 
     LED_STATE = ON; // several pulses in one go speeds up the for loop 
     #if BRIGHTNESS > 0 
     dummy = 0; // increases ON-time 
     #if BRIGHTNESS == 2 
     dummy = 0; // increases ON-time even more 
     #endif 
     #endif 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     #if BRIGHTNESS > 0 
     dummy = 0; 
     #if BRIGHTNESS == 2 
     dummy = 0; 
     #endif 
     #endif 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     #if BRIGHTNESS > 0 
     dummy = 0; 
     #if BRIGHTNESS == 2 
     dummy = 0; 
     #endif 
     #endif 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     #if BRIGHTNESS > 0 
     dummy = 0; 
     #if BRIGHTNESS == 2 
     dummy = 0; 
     #endif 
     #endif 
     LED_STATE = OFF;

由于你可以看到，这使得代码非常难读。我想定义一个预处理器宏，根据BRIGHTNESS的值添加这些虚拟语句。

这是代码看起来应该像：

#define BRIGHTNESS 2 
#define B1 ... // adds dummy=0; when BRIGHTNESS > 0 or else nothing at all 
#define B2 ... 
#define B3 ... 
#define B4 ... 
// inside loop 
     LED_STATE = ON; 
     B1 B2 B3 B4 // adds a number of dummy statements based on the value of BRIGHTNESS 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     B1 B2 B3 B4 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     B1 B2 B3 B4 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     B1 B2 B3 B4 
     LED_STATE = OFF;

更妙的是插入基于可变那些语句的功能：

#define ADD_DUMMIES ... 
// inside loop 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHNESS) 
     LED_STATE = OFF;

我如何定义预处理器宏，以便他们会根据BRIGHTNESS的值插入虚假陈述？

来源

2017-08-02 uzumaki

为什么不使用常规的'if'语句？ – DimChtz

@DimChtz if语句如何提高可读性？ – uzumaki

如果你打算改变LED的亮度，为什么它是恒定的？我错过了什么？ –

这是怎么dummy = 0;语句可以与预处理器的帮助下被添加：

#define BRIGHTNESS 2 
#define _GETFOO(n) _FOO ## n 
#define ADD_DUMMIES(n) _GETFOO(n)() 

#define _FOO0() 
#define _FOO1() dummy = 0; 
#define _FOO2() dummy = 0; dummy = 0; 
#define _FOO3() dummy = 0; dummy = 0; dummy = 0; 
#define _FOO4() dummy = 0; dummy = 0; dummy = 0; dummy = 0; 

uint8_t volatile dummy = 0; 
// inside loop 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHTNESS) 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHTNESS) 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHTNESS) 
     LED_STATE = OFF; 
     LED_STATE = ON; 
     ADD_DUMMIES(BRIGHTNESS) 
     LED_STATE = OFF;

编译器插入相同的存储指令多次其间的线条为BRIGHTNESS使然值，只要它在边界之内。

来源

2017-08-03 01:17:51 uzumaki

如何在C++中使用预处理器指令的帮助下在语句之间插入语句？

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