c - 类型转换为非类型定义的结构

Question

基本上我是从 RTOS 中的另一个线程获取数据。该数据是板上的引脚。所有 IO 端口都位于 iodefine.h 文件的结构/union 中。请参阅以下示例，了解 Micrium 的制作方法:

struct st_portd {
union {
    unsigned char BYTE;
    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;
    } BIT;
} DDR;
unsigned char wk0[31];
union {
    unsigned char BYTE;
    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;
    } BIT;
} DR;
unsigned char wk1[31];
union {
    unsigned char BYTE;
    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;
    } BIT;
} PORT;
unsigned char wk2[31];
union {
    unsigned char BYTE;
    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;
    } BIT;
} ICR;
unsigned char wk3[95];
union {
    unsigned char BYTE;
    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;
    } BIT;
} PCR;
};

如果你问我的话，这是非常聪明的方法。 因此，我将此引脚保存为结构中的 2 个字符，称为“端口”和“引脚”。

struct StepperMotor {
  CPU_INT32U ID;
  CPU_CHAR *EnablePort;
  CPU_CHAR EnablePin;
  CPU_CHAR *DirectionPort;
  CPU_CHAR DirectionPin;
  CPU_CHAR *PulsePort;
  CPU_CHAR PulsePin;
};

我想以这种方式使用该引脚:

(struct st_portd)(steppermotor->PulsePort)->DR.BYTE ^= (1 << steppermotor->PulsePin);

步进电机是结构。 只有这样我才会收到错误消息

request for member 'DR' in something not a structure or union

如何在不为其创建新变量的情况下使用步进电机->PulsePort->DR.BYTE？ 我希望任何人都可以帮助我!

Answer 1

由于您正在转换指针，因此应该将其转换为指向结构的指针，而不是结构本身，如下所示:

((struct st_portd*)steppermotor->PulsePort)->DR.BYTE ^= (1 << steppermotor->PulsePin);

另请注意，括号位置错误。