/* Unlock the Flash Program and Erase Controller. 
This enables write access to the Flash memory. It is locked by default on reset.  */
void flash_unlock(void)
/* Unlock the Flash Program and Erase Controller. 
This enables write access to the Flash memory. It is locked by default on reset.  */
void flash_unlock(void)
{
	FLASH_CR |= FLASH_CR_LOCK;
	FLASH_KEYR = FLASH_KEYR_KEY1;
	FLASH_KEYR = FLASH_KEYR_KEY2;
}