位域结构体有什么实用价值 位操作与硬件寄存器访问实例

// 普通结构体
struct LED_Status {
  unsigned char red : 1;
  unsigned char green : 1;
  unsigned char blue : 1;
};

// 位域结构体
struct LED_Status_BitField {
  unsigned char red : 1;
  unsigned char green : 1;
  unsigned char blue : 1;
};

// 使用
struct LED_Status led1;
struct LED_Status_BitField led2;

printf("Size of LED_Status: %zu bytes\n", sizeof(led1)); // 输出：Size of LED_Status: 3 bytes (通常)
printf("Size of LED_Status_BitField: %zu bytes\n", sizeof(led2)); // 输出：Size of LED_Status_BitField: 1 bytes (通常)

#define REGISTER_ADDRESS 0x40000000 // 假设寄存器的地址是0x40000000
#define BIT3_MASK (1 << 3) // 第3位的掩码

// 设置寄存器的第3位为1
void set_bit3() {
  volatile unsigned int *reg = (volatile unsigned int *)REGISTER_ADDRESS; // volatile关键字防止编译器优化
  *reg |= BIT3_MASK; // 位或操作
}

// 清除寄存器的第3位为0
void clear_bit3() {
  volatile unsigned int *reg = (volatile unsigned int *)REGISTER_ADDRESS;
  *reg &= ~BIT3_MASK; // 位与操作和位取反操作
}

// 读取寄存器的值
unsigned int read_register() {
  volatile unsigned int *reg = (volatile unsigned int *)REGISTER_ADDRESS;
  return *reg;
}

int main() {
  // 示例
  set_bit3(); // 设置第3位
  printf("Register value after setting bit 3: 0x%X\n", read_register());

  clear_bit3(); // 清除第3位
  printf("Register value after clearing bit 3: 0x%X\n", read_register());

  return 0;
}

volatile

volatile

// CAN帧ID的位域结构体
typedef struct {
  unsigned int extended_id : 18;
  unsigned int standard_id : 11;
  unsigned int rtr : 1;
  unsigned int ide : 1;
} CAN_ID_TypeDef;

// CAN帧控制字段的位域结构体
typedef struct {
  unsigned int dlc : 4;
  unsigned int rsv : 3;
  unsigned int brs : 1;
  unsigned int esi : 1;
} CAN_Control_TypeDef;