Copy large size variable to smaller array size by casting in c

I have variable uint16 value, I want to copy it to uint8_t buffer[3]. Is it possible to do (Little endian):

*buffer=*(uint8_t *)&value;

Instead of:

buffer[0] = highByte(value);
buffer[1] = lowByte(value);

Since this replacement cause stm32f7 I2C to not working correctly. Is there any correct casting?

>Solution :

STM32 is little endian so you get the lowest significant byte first:

uint8_t* ptr = (uint8_t*)&value;
uint8_t low  = ptr[0];
uint8_t high = ptr[1];

Doing casts and de-referencing like this is fine for character types only. The above code is assuming that uint8_t is a character type, which is very likely the case (on gcc and other mainstream compilers).

For more info see What is CPU endianness?