format. It is targeted at 32 bit microcontrollers, but is also fit for
other embedded systems with tight (2-10 kB ROM, <1 kB RAM) memory
constraints.(http://koti.kapsi.fi/jpa/nanopb/)

How to use the example:
	1. move examples/nanopb to bsp/xxxx/
	2. enable macro RT_USING_NANOPB in rtconfig.h
	3. regenerate the project file (scons --target=xxxx)
	4. rebuild the project

    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.