#include <stdio.h>
#include <stdint.h>

uint32_t _swap_u32(uint8_t *data) {
  union {
    uint32_t u32;
    uint8_t u8[4];
  } result;
  result.u8[0] = data[2];
  result.u8[1] = data[3];
  result.u8[2] = data[0];
  result.u8[3] = data[1];
  return result.u32;
}

int main()
{
	uint32_t tmp = 1;

	printf("%X\t%X\n", tmp, _swap_u32((uint8_t*) &tmp));
}