对于位域定义的一个小技巧与大家分享一下

whjambo · 发表于 2013-1-28 20:55:06

typedef struct

{

unsigned char b0:1;

unsigned char b1:1;

unsigned char b2:1;

unsigned char b3:1;

unsigned char b4:1;

unsigned char b5:1;

unsigned char b6:1;

unsigned char b7:1;

}REG8_TypeDef;

typedef struct

{

unsigned short b0:1;

unsigned short b1:1;

unsigned short b2:1;

unsigned short b3:1;

unsigned short b4:1;

unsigned short b5:1;

unsigned short b6:1;

unsigned short b7:1;

unsigned short b8:1;

unsigned short b9:1;

unsigned short b10:1;

unsigned short b11:1;

unsigned short b12:1;

unsigned short b13:1;

unsigned short b14:1;

unsigned short b15:1;

}REG16_TypeDef;

typedef struct

{

unsigned long b0:1;

unsigned long b1:1;

unsigned long b2:1;

unsigned long b3:1;

unsigned long b4:1;

unsigned long b5:1;

unsigned long b6:1;

unsigned long b7:1;

unsigned long b8:1;

unsigned long b9:1;

unsigned long b10:1;

unsigned long b11:1;

unsigned long b12:1;

unsigned long b13:1;

unsigned long b14:1;

unsigned long b15:1;

unsigned long b16:1;

unsigned long b17:1;

unsigned long b18:1;

unsigned long b19:1;

unsigned long b20:1;

unsigned long b21:1;

unsigned long b22:1;

unsigned long b23:1;

unsigned long b24:1;

unsigned long b25:1;

unsigned long b26:1;

unsigned long b27:1;

unsigned long b28:1;

unsigned long b29:1;

unsigned long b30:1;

unsigned long b31:1;

}REG32_TypeDef;

//定义位域:R32(GPIOA->ODR)b0=1等同于GPIOA->ODR的bit0置1

#define R8(reg) ((volatile REG8_TypeDef*)&(reg))->

#define R16(reg) ((volatile REG16_TypeDef*)&(reg))->

#define R32(reg) ((volatile REG32_TypeDef*)&(reg))->

感觉是不是很好用呢？同理在其他单片机上也可以这样定义。

Pony279 · 发表于 2013-1-28 21:44:58

C/C++ 标准上并没有对MSB和LSB的定义顺序的严格定义，比如在其它的平台或者编译器可能是
typedef struct
{
unsigned char b7:1; // b7 定义在前
unsigned char b6:1;
unsigned char b5:1;
unsigned char b4:1;
unsigned char b3:1;
unsigned char b2:1;
unsigned char b1:1;
unsigned char b0:1;
}REG8_TypeDef;

whjambo · 发表于 2013-1-28 23:32:06

回复【2楼】Pony279:

C/C++ 标准上并没有对MSB和LSB的定义顺序的严格定义，比如在其它的平台或者编译器可能是
typedef struct
{
unsigned char b7:1; // b7 定义在前
unsigned char b6:1;
unsigned char b5:1;
unsigned char b4:1;
unsigned char b3:1;
unsigned char b2:1;
unsigned char b1:1;
unsigned char b0:1;
}REG8_TypeDef;

---------------------------------
谢谢补充，不过Keil和IAR好像都是低地址在前，呵呵

jswd · 发表于 2013-1-29 10:32:51

回复【楼主位】whjambo:
---------------------------------
位段好像必须是int，uint等类型，不能是char型吧，
我也想用这种方法定义位变量，不过还没有理清楚该怎么对应，希望大家指点一下

whjambo · 发表于 2013-1-31 13:31:00

回复【4楼】jswd:
---------------------------------
那要看你定义的位域是几位的，8位：unsigned char，16位：unsigned short，32位：unsigned long，
64位（一般用不到）：unsigned long long。
至于为什么用short 不用int，是因为不同单片机编译器的int类型不一样，对于8位单片机如avr一般int是16位，但是ARM一般int是32位的，但是short是统一的16位，不会发生兼容问题。