fantemp

Temperature-controlled fan firmware (ATmega328P, 16 MHz), rewritten on libavr: thermistor on ADC0 sampled free-running and averaged over 1000 conversions, fan on OC0B at 50 kHz, 115200 Bd serial console (help lists the commands), temperature histogram persisted to EEPROM, watchdog-reset path into a boot-section bootloader.

The Steinhart–Hart math of the legacy firmware (runtime doubles + libm log) is gone: the Beta equation and the cubic fan curve are evaluated consteval into flash tables — the firmware itself never touches floating point.

libavr rides as the libavr/ submodule, pinned to the commit this firmware builds against; LIBAVR_ROOT (cache or environment) overrides it for development against a working tree:

git submodule update --init libavr
cmake --preset atmega328p-generated
cmake --build --preset atmega328p-generated

Atmel Studio

master carries a Studio solution, so this branch does too: ide/fantemp.atsln builds the same firmware — byte-identical .text and .data to the CMake build — from the same sources, with the flags mirrored by hand.

Studio finds libavr in the submodule, at $(MSBuildProjectDirectory)\..\libavr\include — correct by construction, and anchored to the project rather than written relative to the generated makefile, which runs from the configuration's output directory and would need a different number of ... Unlike the CMake build there is no LIBAVR_ROOT to point elsewhere: an environment variable set in a shell is not visible to Studio launched from the Start menu — which is what the submodule answers.

It also needs a GCC 16.1 toolchain registered as flavour avr-g++-16.1.0; nothing older can compile -std=c++26.

One generated file is required before the project will load, and one command checks the flags have not drifted (both from libavr's tools/atmelstudio/):

python ../libavr/tools/atmelstudio/componentinfo.py \
    ide/fantemp.componentinfo.xml --device ATmega328P
python ../libavr/tools/atmelstudio/check-flags.py --solution ide/fantemp.atsln \
    --compile-commands build/atmega328p-generated/compile_commands.json \
    --log build/atmelstudio.log

CMake remains the build system; the solution is there so the project opens in Studio as its predecessor did. Only the Release configuration is gated against CMake — the presets define no debug build — and Debug carries the -Og -gdwarf-4 pair libavr's own debug preset uses.

Legacy (yazoalfa submodules) stays on master.