Add Slice 5 ADAU1701 runtime audio control (firmware 0.5.0).

Safeload mixer/EQ/master on the ADAU1701, persist AudioProfile in NVS,
expose /api/audio routes and web UI controls, with host tests and manual sync.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/components/core/test/CMakeLists.txt

@@ -22,6 +22,15 @@ add_library(digiradio_core STATIC
     "${CORE_SRC_DIR}/EmbeddedBlobReader.cpp"
     "${CORE_SRC_DIR}/TunerJson.cpp"
     "${CORE_SRC_DIR}/FrequencyKHz.cpp"
+    "${CORE_SRC_DIR}/GainDb.cpp"
+    "${CORE_SRC_DIR}/FrequencyHz.cpp"
+    "${CORE_SRC_DIR}/EqBandIndex.cpp"
+    "${CORE_SRC_DIR}/BiquadCoefficients.cpp"
+    "${CORE_SRC_DIR}/BiquadDesign.cpp"
+    "${CORE_SRC_DIR}/MixerState.cpp"
+    "${CORE_SRC_DIR}/EqProfile.cpp"
+    "${CORE_SRC_DIR}/AudioProfile.cpp"
+    "${CORE_SRC_DIR}/AudioProfileJson.cpp"
 )
 target_include_directories(digiradio_core PUBLIC
     "${CMAKE_CURRENT_SOURCE_DIR}/../include"
@@ -46,3 +55,11 @@ add_test(NAME tuner_json_test COMMAND tuner_json_test)
 add_executable(frequency_khz_test frequency_khz_test.cpp)
 target_link_libraries(frequency_khz_test PRIVATE digiradio_core)
 add_test(NAME frequency_khz_test COMMAND frequency_khz_test)
+
+add_executable(biquad_design_test biquad_design_test.cpp)
+target_link_libraries(biquad_design_test PRIVATE digiradio_core)
+add_test(NAME biquad_design_test COMMAND biquad_design_test)
+
+add_executable(audio_profile_json_test audio_profile_json_test.cpp)
+target_link_libraries(audio_profile_json_test PRIVATE digiradio_core)
+add_test(NAME audio_profile_json_test COMMAND audio_profile_json_test)

Software/components/core/test/audio_profile_json_test.cpp

@@ -0,0 +1,66 @@
+/**
+ * @file    audio_profile_json_test.cpp
+ * @brief   Host tests for AudioProfile JSON round-trip.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * @author  Michele Bigi
+ * @date    2026-07-06
+ */
+
+#include "core/AudioProfile.hpp"
+#include "core/AudioProfileJson.hpp"
+#include "core/EqBandIndex.hpp"
+#include "core/FrequencyHz.hpp"
+#include "core/GainDb.hpp"
+
+#include <cstdlib>
+#include <iostream>
+
+namespace {
+
+[[nodiscard]] int runRoundTripTest()
+{
+    core::AudioProfile profile = core::AudioProfile::factoryDefault();
+    const auto band = core::EqBandIndex::tryFromIndex(2U);
+    const auto gain = core::GainDb::tryFromDb(3.0F);
+    const auto center = core::FrequencyHz::tryFromHz(500U);
+    if (!band || !gain || !center) {
+        std::cerr << "test setup failed\n";
+        return EXIT_FAILURE;
+    }
+    profile.eq.setBand(*band,
+                       core::EqBandSettings{
+                           .gain = *gain,
+                           .center = *center,
+                           .q = 2.0F,
+                       });
+
+    const std::string json = core::serializeAudioProfileJson(profile);
+    const auto parsed = core::parseAudioProfileJson(json);
+    if (!parsed) {
+        std::cerr << "parse failed\n";
+        return EXIT_FAILURE;
+    }
+
+    const auto& b = parsed->eq.band(*band);
+    if (b.gain.value() != 3.0F || b.center.value() != 500U
+        || b.q != 2.0F) {
+        std::cerr << "round-trip mismatch\n";
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}
+
+} // namespace
+
+int main()
+{
+    if (runRoundTripTest() != EXIT_SUCCESS) {
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}

Software/components/core/test/biquad_design_test.cpp

@@ -0,0 +1,68 @@
+/**
+ * @file    biquad_design_test.cpp
+ * @brief   Host tests for ADAU biquad design and fixpoint conversion.
+ *
+ * DigiRadio firmware — https://github.com/manvalan/DigiRadio
+ *
+ * Copyright 2026 Michele Bigi
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * @author  Michele Bigi
+ * @date    2026-07-06
+ */
+
+#include "core/BiquadDesign.hpp"
+#include "core/FrequencyHz.hpp"
+#include "core/GainDb.hpp"
+
+#include <cmath>
+#include <cstdlib>
+#include <iostream>
+
+namespace {
+
+[[nodiscard]] int runUnityGainFixpointTest()
+{
+    const auto gain = core::GainDb::zero();
+    const std::int32_t fix = core::gainDbToLinearFixpoint(gain);
+    if (fix != 0x00800000) {
+        std::cerr << "expected 0 dB fixpoint 0x00800000, got 0x"
+                  << std::hex << fix << std::dec << '\n';
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}
+
+[[nodiscard]] int runFlatBiquadTest()
+{
+    const core::BiquadCoefficients flat = core::designFlatEq();
+    if (std::fabs(flat.b0 - 1.0F) > 0.001F || std::fabs(flat.b1) > 0.001F
+        || std::fabs(flat.b2) > 0.001F || std::fabs(flat.a0) > 0.001F
+        || std::fabs(flat.a1) > 0.001F) {
+        std::cerr << "flat biquad coefficients unexpected\n";
+        return EXIT_FAILURE;
+    }
+
+    const auto center = core::FrequencyHz::tryFromHz(1000U);
+    const auto zero = core::GainDb::zero();
+    const core::BiquadCoefficients peaking =
+        core::designPeakingEq(*center, zero, 1.414F);
+    if (std::fabs(peaking.b0 - 1.0F) > 0.001F) {
+        std::cerr << "0 dB peaking should match flat b0\n";
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}
+
+} // namespace
+
+int main()
+{
+    if (runUnityGainFixpointTest() != EXIT_SUCCESS) {
+        return EXIT_FAILURE;
+    }
+    if (runFlatBiquadTest() != EXIT_SUCCESS) {
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}