add CLAUDE.md for AI assistant context

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Overview
+
+MEMLNaut-NISPS (Neural Interactive Shaping of Parameter Spaces) is firmware for the MEMLNaut hardware platform - a custom embedded audio device built on Raspberry Pi Pico (RP2040). It implements interactive machine learning for real-time audio synthesis and processing, enabling users to shape sound parameters through reinforcement learning.
+
+Project documentation: https://musicallyembodiedml.github.io/memlnaut/approaches/nisps
+
+## Build System
+
+This is an Arduino project targeting Raspberry Pi Pico. Build and upload using Arduino IDE or arduino-cli with the earlephilhower/pico board package.
+
+```bash
+# Initialize submodules (required for memllib and memlp)
+git submodule update --init --recursive
+
+# Build (adjust port as needed)
+arduino-cli compile --fqbn rp2040:rp2040:rpipico -b 115200 MEMLNaut-NISPS.ino
+arduino-cli upload --fqbn rp2040:rp2040:rpipico -p /dev/ttyACM0 MEMLNaut-NISPS.ino
+```
+
+## Architecture
+
+### Dual-Core Design
+
+The RP2040's dual cores are used for separation of concerns:
+- **Core 0**: UI loop, ML inference, hardware interface polling (5ms period)
+- **Core 1**: Real-time audio processing, parameter updates, MIDI polling
+
+Inter-core synchronization uses memory barriers (`MEMORY_BARRIER()`, `WRITE_VOLATILE()`, `READ_VOLATILE()`) and RP2040 queues (`queue_t`).
+
+### Mode System
+
+The active mode is selected at compile-time via `#define MEMLNAUT_MODE_TYPE` in `MEMLNaut-NISPS.ino`. Modes implement the `MEMLNautMode` concept (see `modes/MEMLNautMode.hpp`):
+
+| Mode | Purpose |
+|------|---------|
+| `MEMLNautModeChannelStrip` | Audio channel strip (EQ, compression, gain staging) |
+| `MEMLNautModePAFSynth` | PAF (Phase Aligned Formant) synthesis with MIDI |
+| `MEMLNautModeXIASRI` | Audio-reactive mode using machine listening analysis |
+| `MEMLNautModeSoundAnalysisMIDI` | Sound analysis with MIDI output |
+
+### Voice Spaces
+
+Voice spaces map ML output parameters to audio engine parameters. They are defined as lambda functions that translate a normalized parameter array into synthesizer/processor settings. See `voicespaces/` for examples:
+- PAF synth presets: `VoiceSpace1.hpp`, `VoiceSpaceQuadDetune.hpp`, etc.
+- Channel strip presets: `voicespaces/ChannelStrip/basic.hpp` (Neve, SSL emulations)
+
+### Key Components
+
+- **IMLInterface** (`IMLInterface.hpp`): Interactive ML interface using an MLP for inference/training
+- **InterfaceRL**: Reinforcement learning interface from memllib that handles joystick input and learning
+- **AudioAppBase**: Template base class for audio applications
+- **XiasriAnalysis**: Real-time audio feature extraction (pitch, aperiodicity, energy, brightness)
+
+### Submodules (in `src/`)
+
+- **memllib**: Hardware abstraction, audio drivers, synth components, RL interfaces
+- **memlp**: MLP (Multi-Layer Perceptron) implementation for embedded ML
+- **daisysp**: DSP library (filters, drums, effects, synthesis)
+
+## Memory Sections
+
+The codebase uses RP2040-specific memory placement:
+- `AUDIO_MEM` / `AUDIO_FUNC`: Place audio-critical code/data in SRAM
+- `APP_SRAM` / `__not_in_flash("app")`: Keep frequently-accessed data out of flash
+
+## Audio Parameters
+
+Sample rate is defined in `AudioDriver::GetSampleRate()`. The audio callback `audio_block_callback` runs on Core 1 and processes stereo audio (`stereosample_t`).