The main purpose of this new COM implementation is that it is
much simpler, and requires less code space. This takes a bit
of the pressure off of the CC bootloader which was right at
the limit of available code space in the bootloader partition.
This is not intended to ever be used by the application.
This driver also formalizes the assumptions in the bootloader's
usage of the COM layer. All messages are assumed to arrive
in atomic chunks from the HID layer.
This can be used by the GCS firmware uploader widget to boot
the firmware with a (temporarily) defaulted hwsettings uavo
so that a user can easily recover from a bad/incompatible
hwsettings configuration without wiping all settings.
This uses the same mechanism that the BootFault auto-recovery
code already uses in the CC firmware. The auto-recovery is
triggered by setting the failed-boot counter to a maximum
value forcing recovery on the next FW init.
Now that every bootloader build has a board info blob,
make all fw and bl images use it.
The following MACROS are removed:
BOARD_TYPE, BOARD_REVISION, BOOTLOADER_VERSION,
START_OF_USER_CODE, HW_TYPE
These values are now ONLY available from the bootloader
flash via the pios_board_info_blob symbol. These values
must not be #defined or otherwise hard-coded into the
firmware in any way. The bootloader flash is the only
valid source for this information.
NOTE: To ensure that we have an upgrade path from an
old bootloader (without board_info_blob) to a
new bootloader (with board_info_blob), it is
essential that the bu_* targets do not depend
on (or validate) the board_info_blob being present
in the bootloader flash.
