# fantemp

Temperature-controlled fan firmware (ATmega328P, 16 MHz), rewritten on
[libavr](https://git.blackmark.me/avr/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:

```sh
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/`):

```sh
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`.