Normally, the OSTC3 will always start writing dives at the first entry
in the TOC (Table of Contents). Therefore, uninitialized entries can
only be present after the last dive. However due to a minor firmware
bug, resetting the logbook erases the TOC but leaves the internal dive
counter unchanged. The consequence is that the next dive will still be
stored at the corresponding next TOC entry, while all previous TOC
entries have been erased.
As a workaround, we simply ignore uninitialized entries, unless we have
already found at least one dive.
The OSTC 3 dataformat does contain the profile length twice: once in the
main 256 byte header, and again in the small profile header. However due
to a firmware bug, both values are not identical. The value in the main
header is wrong and 3 bytes larger than the value in the small profile
header. This bug was fixed in firmware version 0.93.
Unfortunately we rely on the length in the main header to calculate the
number of bytes to read when downloading the dive. The consequence is
that for all dives recorded with firmware 0.93 or later, the length is
calculated incorrectly, and the download fails. Luckily the firmware
version is stored in the main header too, and we can adjust the length
calculation accordingly.
Although the communication protocol of the OSTC3 is nearly identical to
that of the Frog, the different size parameters make it hard to share
the code easily. On top of that, if we ever implement native bluetooth
communication support, we'll need a completely separate backend anyway.
Therefore the Frog backend is simply duplicated, with a few OSTC3
specific changes applied here and there.
The existing ostc parser is upgraded to support the new OSTC3 data
format.
