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+# Build
+
+Standalone CRDOP (**MAX25-SoftModem** — MAX25-SoftModem) — embedded `vendor/ardopcf/`, no submodules.
+
+## Requirements
+
+- CMake ≥ 3.16
+- **GCC** or **Clang / LLVM**
+- Platform libraries (see table below)
+- Optional tests: **cmocka** (Linux, *BSD)
+
+## Platform matrix (tested)
+
+| OS | Toolchain | Audio / libs | Status |
+|----|-----------|----------------|--------|
+| **Linux** | GCC, Clang | `libasound2-dev`, `pkg-config` | tested |
+| **FreeBSD** | GCC, Clang | `alsa-lib`, `pkgconf` | tested |
+| **OpenBSD / NetBSD** | GCC, Clang | `alsa-lib` if available | experimental |
+| **Windows** | MinGW-w64, MSVC | WinMM (built-in) | **untested** |
+| **macOS** | Clang (Xcode) | CoreAudio (built-in) | **untested** |
+
+Other operating systems are not tested.
+
+### Debian / Ubuntu
+
+```bash
+sudo apt install build-essential cmake libasound2-dev pkg-config
+sudo apt install libcmocka-dev    # optional unit tests
+```
+
+### FreeBSD
+
+```bash
+pkg install cmake alsa-lib pkgconf cmocka
+```
+
+### macOS
+
+```bash
+xcode-select --install
+# or: brew install cmake
+```
+
+### Windows (MinGW-w64 on Linux host)
+
+```bash
+sudo apt install mingw-w64
+CRDOP_TOOLCHAIN=x86_64-w64-mingw32 ./scripts/build-crdop.sh
+# → build/crdopc.exe
+```
+
+Native Windows: Visual Studio 2022+ with CMake, or MSYS2 MinGW.
+
+## Build
+
+```bash
+./scripts/build-crdop.sh
+CC=clang ./scripts/build-crdop.sh
+./scripts/test-all.sh              # smoke + cmocka (Unix)
+```
+
+Output: `build/crdopc` (Windows: `build/crdopc.exe`)
+
+## Install
+
+```bash
+./scripts/install-crdop.sh                    # → /usr/local
+CRDOP_PREFIX=$HOME/.local ./scripts/install-crdop.sh
+```
+
+Installs:
+
+| Path | Contents |
+|------|----------|
+| `bin/crdopc` | Modem binary |
+| `bin/crdop` | Profile launcher (`scripts/crdopc`) |
+| `share/crdop/` | INI examples, `VERSION` |
+
+Run: `crdop` or `CRDOP_INI=~/.config/crdop/crdop.ini crdop`
+
+## Cross-compile (Linux host)
+
+```bash
+CRDOP_TOOLCHAIN=aarch64-linux-gnu ./scripts/build-crdop.sh
+CRDOP_TOOLCHAIN=arm-linux-gnueabihf ./scripts/build-crdop.sh
+CRDOP_TOOLCHAIN=x86_64-w64-mingw32 ./scripts/build-crdop.sh
+```
+
+## Troubleshooting
+
+| Problem | Fix |
+|---------|-----|
+| `vendor/ardopcf missing` | Full repo checkout |
+| No ALSA (Linux/BSD) | Install dev package / `alsa-lib` port |
+| macOS build fails | Xcode CLI tools; CMake ≥ 3.16 |
+| Tests skipped | Install cmocka dev package |
+| Stale build | `rm -rf build && ./scripts/build-crdop.sh` |
+
+Vendor refresh (maintainers): `./scripts/refresh-vendor-ardopcf.sh`