union value issue

[赵子成]

Hi, everyone,

Now I use S32K146, I define a union type variable as follow:

typedef union unCanFrameData
{
UINT8 u8Data[CAN_FRAME_DATA_LEN]; ///< 8 uint8 data
UINT16 u16Data[4]; ///< 4 uint16 data
UINT32 u32Data[2]; ///< 2 uint32 data
}UN_CAN_FRAME_DATA;

But when I set the u16Data[2]:

unData.u16Data[2] = 2000

I get the follow result:

The problem is that the u16Data[2] is 2000, but the u8Data[4] and u8Data[5] is 0, the data is not Coincident.

Can anyone help me? Thanks.

[1642280511]

hello,I'm Chinese people，if you too,can you tell me your qq number，I'd like to ask you some questions。thank you so mach.

[赵子成]

Hi, I am sorry. I didn't use QQ.

I you would, you can ask me via this platform.

[BlackNight]

I quickly tried that, but I get a reasonable result:

with

  typedef uint8_t UINT8;
  typedef uint16_t UINT16;
  typedef uint32_t UINT32;

#define CAN_FRAME_DATA_LEN 8
  typedef union unCanFrameData
  {
  UINT8 u8Data[CAN_FRAME_DATA_LEN]; ///< 8 uint8 data
  UINT16 u16Data[4]; ///< 4 uint16 data
  UINT32 u32Data[2]; ///< 2 uint32 data
  }UN_CAN_FRAME_DATA;

and

unData.u16Data[2] = 2000;

I believe it could be some compiler settings you are using (can you share a small example project)?

I used the S32K144 (don't think it matters), but can you check that 0x2000'ef58 you indeed have RAM?

I hope this helps,

Erich

[赵子成 · Accepted solution]

Hi Erich.

I have solved this issue.

The root is that I define UINT16 as unsigned int.

In S32K CPU, unsigned int is 4 bytes long. Not 2 bytes.

This make the union alain failure.

Thanks.

[赵子成]

Hi Erich,

I think it could be something about union settings. Even I set the union variable to be global, it happen this error again:

Could you tell me where to set the union or the data type setting?

Thanks.