Update bootloader to detect old and new version

[hathach]

Current there are 2 bootloader version.

• old bootloader (0.0): used by already-on-the-shelf blefriend board
• new bootloader (0.5): used by all other products.

The major difference in android's point of view is that the new bootloader requies an Init Packet http://developer.nordicsemi.com/nRF51_SDK/doc/7.2.0/s110/html/a00065.html to perform DFU. It is a separated binary file containing metadata of firmware image such as CRC, Revision etc ... Init Packet is generated during firmware make and included together with the firmware hex (e.g blefriend_s110_xxaa_dfu_init.bin )

To detect if the bootloader is old or new version:

• new version always have the bootloader revision characteristics (3rd chars) with the value at least 0x0005 (little endian)
• old version is either has the revision characteristic = 0x0000 or does not have the char at all when it is in bootloader mode.

[hathach]

or since old version of bootloader is used for blefriend only, we can simply determine the old bootloader by checking if the board is blefriend or not.

[microbuilder]

This issue has been resolved with a firmware update on the nRF51 side (as of version 0.5.0).