def set_register(self, addr, data):
        """Sets an arbitrary register at @addr and subsequent registers depending
        on how much data you decide to write. It will automatically fill extra
        bytes with zeros. You cannot write more than 14 bytes at a time.
        @addr should be a static constant from the Addr class, e.g. Addr.Speed"""
        assert len(data) <= 14, "Cannot write more than 14 bytes at a time"
        cmd = chr(addr) + chr(len(data) | 0x80)
        for byte in data:
            cmd += chr(cast_to_byte(byte))
        cmd += (16 - len(cmd)) * chr(0)
        self._dev.send_bytes(cmd)