BlackMark
ba37ecea04
libavr's guidance binds this repo too, and until now nothing here checked it - `ctest` runs `libavr_format_test()` over this tree's own sources now (rules 11 and 33), skipping rather than passing where clang-format is absent. It caught drift on its first run: a file written this week and edited after formatting. Where the README states a measured size, `libavr_size_claim_test()` holds it to the image and holds the image to the prose: advancing the library pin moved three of these across the fleet with nothing saying so, and re-recording one now requires the sentence that quotes it to move too. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
85 lines
3.2 KiB
C++
85 lines
3.2 KiB
C++
// Compile-only battery, built with the cross compiler so the target's 16-bit
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// int is exercised. Two of this firmware's three numeric surfaces are decided
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// entirely at compile time - the fan curve and the thermistor table - and the
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// third, quarter-degrees to whole ones, is the arithmetic between them.
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#include <cstdint>
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#include "curve.hpp"
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#include "thermistor.hpp"
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namespace {
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using app::thermistor::whole_degrees;
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// Rounding to nearest, across zero. A negative quotient truncates toward zero
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// in C, so a `(q + 2) / 4` reads -3.00 C as -2 and every case below the tie
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// with it; the arithmetic shift floors, which is what these hold it to.
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static_assert(whole_degrees(0) == 0);
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static_assert(whole_degrees(1) == 0); // +0.25
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static_assert(whole_degrees(2) == 1); // +0.50, the tie
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static_assert(whole_degrees(3) == 1); // +0.75
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static_assert(whole_degrees(4) == 1); // +1.00
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static_assert(whole_degrees(-1) == 0); // -0.25
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static_assert(whole_degrees(-2) == 0); // -0.50, the tie, toward zero
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static_assert(whole_degrees(-3) == -1);
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static_assert(whole_degrees(-4) == -1);
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static_assert(whole_degrees(-12) == -3);
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static_assert(whole_degrees(-160) == -40); // the table's own floor
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static_assert(whole_degrees(500) == 125); // and its ceiling
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// The curve is held at zero below the temperature the fan starts at, and
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// saturates inside the table's window rather than at its edge.
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using app::curve::detail::duty_entry;
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static_assert(duty_entry(app::curve::start_celsius - 1) == 0);
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static_assert(duty_entry(app::curve::start_celsius) == 0);
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static_assert(duty_entry(30) == 7);
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static_assert(duty_entry(40) == 36);
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static_assert(duty_entry(49) == 93);
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static_assert(duty_entry(50) == 100);
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static_assert(duty_entry(99) == 100);
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// Monotone across the whole table: a warmer reading never asks for less air.
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consteval bool curve_rises()
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{
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for (std::int32_t t = 1; t < 100; ++t) {
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if (duty_entry(t) < duty_entry(t - 1)) {
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return false;
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}
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}
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return true;
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}
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static_assert(curve_rises());
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// The thermistor table, anchored where the Beta equation fixes it rather than
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// against numbers this file computed the same way: the divider reads the
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// thermistor's nominal resistance at
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// adc = full_scale * nominal / (series + nominal), and the equation's own
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// definition puts that count at the nominal temperature.
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using app::thermistor::detail::quarters_entry;
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inline constexpr std::int32_t nominal_count =
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static_cast<std::int32_t>(app::thermistor::adc_full_scale * app::thermistor::nominal_resistance /
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(app::thermistor::series_resistor + app::thermistor::nominal_resistance));
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static_assert(quarters_entry(nominal_count / 4) >= 100); // 25.00 C, in quarters
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static_assert(quarters_entry(nominal_count / 4 + 1) < 100); // and the step below it
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// Both clamps, at the ends the divider cannot leave.
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static_assert(quarters_entry(0) == 125 * 4);
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static_assert(quarters_entry(255) == -40 * 4);
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// An NTC on this divider falls with the count: more counts is more resistance
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// is a colder sensor, over every step of the table.
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consteval bool thermistor_falls()
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{
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for (std::int32_t i = 1; i < 256; ++i) {
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if (quarters_entry(i) > quarters_entry(i - 1)) {
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return false;
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}
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}
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return true;
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}
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static_assert(thermistor_falls());
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} // namespace
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