C语言 结构体、联合、位段

例如，有一些寄存器，寄存器有一些位，每个位都控制不同的设置，要是想单独设置某一个位的值，用位段就是一个比较好的方法，

寄存器例子：

 第一种方法：如果内存小的话可能造成堆栈溢出

 union _GSTAT_Register
{
      uint32_t value;
      struct GSTAT_Register *GSTAT_Register_bit;
};
  struct GSTAT_Register {

    uint8_t reset:1; // Indicates that the IC has been reset since the last read access to GSTAT
    uint8_t drv_err:1; // Indicates that the driver has been shut down due to overtemperature or short circuit detection since the last read access
    uint8_t uv_cp:1; // Indicates an undervoltage on the charge pump. The driver is disabled in this case.
  };

第二种方法：比第一种占用的更小

 union _GSTAT_Register
 {
       uint32_t value;
      struct  {

           uint8_t reset:1; // Indicates that the IC has been reset since the last read access to GSTAT
           uint8_t drv_err:1; // Indicates that the driver has been shut down due to overtemperature or short circuit detection since the last read access
           uint8_t uv_cp:1; // Indicates an undervoltage on the charge pump. The driver is disabled in this case.
         }GSTAT_Register;
 };

union _GSTAT_Register gstat = {0};//调用先出事化
gstat.GSTAT_Register.reset = 1;
gstat.GSTAT_Register.uv_cp =1;
sendData(GSTAT, gstat.value);

位段在使用中可能是从第零位开始0,1，2,3,4等，也可能是从最高位开始

我这台是从零开始。

由于是一位一位操作所得到的数就是二进制数，不需要进制转换，与想传入的十进制数或者十六进制数一致。