AURIX™ Forum Discussions

[User22282]

Hello!
I am trying to rewrite my code from other MCU to TC234. And when i try to cast Can bus data to (uint16_t) like this:

- uint16_t var = *(uint16_t*)pCanData;

CPU goes to IfxCpu_Trap_instructionError(). And the same happends if i try to write field of casted struct like this:

Header_t *pxHeader = (Header_t *)byteArrayGetData(&pCtx->byteArray);
pCtx->sessionCnt = pxHeader->sessions;

What i do wrong, or TC234 can't do this operations?

[MoD]

This will be happen when e.g. pCanData is not 16 bit aligned. Check the TIN of the trap, I expect it is 4 (ALN - Data Address Alignment).
Same occurs with the struct. You must make sure that the address of the byteArray is 32 bit aligned.

[User22282]

Thank you for answering!

TIN of the trap is realy 4. If I understand it right uint8_t canData[8] most be 16bit aligned;
so it's no way to do forward cast from canData to uint16_t like this

*(uint16_t*)&canData[0], the only way is used bit shift - (canData[0] | canData[1] << 😎

howeever how can I sure that adress of byteArray is 32 bit aligned? Is that some compiler setting? Or I most create all structures with padding.

[MoD · Accepted solution]

You can change the definition e.g. uint8_t canData[8] IFX_ALIGN(IFX_ALIGN_16), then canData[0] is 16 bit aligned.
Same works for the byteArray. If you add an IFX_ALIGN(IFX_ALIGN_32) then the struct is 32 bit aligned.
Maybe there is also a compiler option to use always 32 bit address for begin of structs and fields. Please check the compiler documentation for such a setting if exist.

[User22282]

Thank you for answer!