OXape reports: http://www.rt-thread.org/phpBB3/topic3939.html
          driver/ringbuffer: when data length is bigger than space length
          for rb, the read_index in rb is not update.
    When length > space, update the read_index, the bug can be fix, and
          works fine.

If there is no SHT$$INIT_ARRAY, calling
$Super$$__cpp_initialize__aeabi_() will fault. At least until Keil5.12
the problem still exists. So we have to initialize the C++ runtime our
own.

Currently only lpc43xx is supported.

As we are sending C continuously, there is a chance that the
sender(remote) receive an C after sending the first handshake package.
So the sender will interpret it as NAK and re-send the package. So we
just ignore it and proceed.