fp2conv

"FP2" is a 16-bit data type that is defined to store values
from +/-0.001 to +/-7999 (up to 4 significant digits).

NOTE: This data type is not my invention; it is already used on
numerous embedded devices.

This library provides functions to convert these data types to and
from strings, see fp2conv.h for details. The data type is defined
as follows:

The meanings of bits 14-13 (decimal position) are defined as follows:

Note that identical values can be represented in different ways. This
library uses the above value range to decide the storage format, thus
for example the integer 1 is stored as 0x63E8, even though it could
also be stored as 0x4064, 0x200A, or 0x0001. As one exception,
zero (0) is stored as 0x0000. Note the conversion from FP2 to string
can handle all of the aforementioned values.

Though theoretically 13 bits can store values from 0 to 8191,
this data type defines the maximum value at 7999; in addition,
the following special values are defined:

* This is not part of the original specification, but as far as I can
tell this value should never occur otherwise, so this code uses it to
indicate that the conversion could not be performed.

Compilation

Using the provided Makefile, you can simply run make to build
libfp2conv.so, and make test to build and run test_fp2conv.c.
The library and headers can be installed via sudo make install.
Tested on Linux with gcc 7.5.0.

Arduino

The fp2conv.c / fp2conv.h files were tested to be working on an
Arduino MKR series board with a SAMD21 processor
using the Arduino IDE 2.0.0.

The source files can be installed to your local Arduino library path
with make ardulibinst, assuming the default environment on Linux.

Python

Simple Python bindings are provided in pyfp2conv.py with tests in tests/.
Tested on Python 3.10 on Linux.

Perl

Simple Perl FFI bindings are provided in lib/Data/FP2.pm with tests in t/.
The CPAN module FFI::Platypus is required.
Tested on Perl 5.34 and 5.28 on Linux.

Note: If FFI::Platypus fails to build due to a missing xlocale.h,
a workaround is: cd /usr/include && sudo ln -si locale.h xlocale.h

Tests

All tests can be run via the included shell script prove.sh.

Author, Copyright, and License

Copyright (c) 2022 Hauke Daempfling haukex@zero-g.net
at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB),
Berlin, Germany, https://www.igb-berlin.de/

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see https://www.gnu.org/licenses/.