https://github.com/merbanan/rtl_433/issues/2014: the protocol was fully
reverse-engineered in the issue (OOK PPM timing, checksum, 2's-complement
temperature confirmed via a freezer test, battery-low bit confirmed via
an old-vs-fresh-battery comparison, even a working Arduino sketch) but
never ported into rtl_433 before the reporter lost interest.
Verified against all of the issue's distinct examples via -y, including
a low-battery reading and a second physical unit from a neighbor's
device. One correction: the original post's "-22.6 C" label for one
capture doesn't match the checksum-verified 2's-complement decode (which
gives +22.6 C) -- that label predates the freezer test that established
the actual encoding, so it looks like an early mislabeling rather than a
real discrepancy.
The wire checksum is only 4 bits, too weak to reject noise reliably on
its own -- enabling this against the full rtl_433_tests corpus produced
two dozen false positives on unrelated weather-sensor protocols with
similar OOK/PPM timing. Added a flags-nibble check and a plausible
temperature range, both satisfied by every real capture available, which
eliminates all of them.
e48537c525