diff --git a/README.md b/README.md
index 87a3fc5..06914ad 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,104 @@
 # NeoECU Tooling
 
 Unified CLI tooling for building and flashing NeoECU firmware
+
+## Configuration
+
+Run commands from anywhere inside a project that contains `neoecu.toml`. The tool walks up the directory tree until it finds that file.
+
+`neoecu.toml` uses a `[build]` table. A core is considered configured only when both its directory and type are present:
+
+```toml
+[build]
+m7_dir = "path/to/cm7/project"
+m7_type = "ST"
+m4_dir = "path/to/cm4/project"
+m4_type = "Zephyr"
+```
+
+Supported core types are `ST` for CM7 and `Zephyr` for CM4. If either the CM7 or CM4 keys are missing or incomplete, that core is skipped and the tool runs as a single-core project for the core that is fully configured.
+
+Examples:
+
+```toml
+[build]
+m7_dir = "STM32"
+m7_type = "ST"
+```
+
+```toml
+[build]
+m4_dir = "Zephyr"
+m4_type = "Zephyr"
+```
+
+## Commands
+
+### `neoecu build`
+
+Builds the configured firmware cores. With both cores configured, this builds CM7 first with CMake and CM4 second with West/Zephyr. With only one fully configured core, only that core is built.
+
+Options:
+
+- `--debug`: build CM7 with the `Debug` CMake preset. If omitted, CM7 uses `Release`.
+- `--release`: build CM7 with the `Release` CMake preset.
+- `--clean`: clean before building. CM7 uses CMake `--clean-first`; CM4 uses West pristine rebuild.
+- `--CM7`: build only the CM7 core.
+- `--CM4`: build only the CM4 core.
+
+Examples:
+
+```sh
+neoecu build
+neoecu build --debug
+neoecu build --release --clean
+neoecu build --CM7
+neoecu build --CM4 --clean
+```
+
+### `neoecu flash`
+
+Flashes the configured firmware cores with J-Link. With both cores configured, CM4 is flashed first and CM7 second. With only one fully configured core, only that core is flashed.
+
+Options:
+
+- `--CM7`: flash only the CM7 core.
+- `--CM4`: flash only the CM4 core.
+
+Examples:
+
+```sh
+neoecu flash
+neoecu flash --CM7
+neoecu flash --CM4
+```
+
+### `neoecu init`
+
+Initializes the configured project cores. For CM7, it runs the CMake `Debug` and `Release` presets and performs an initial debug build. For CM4, it installs West and Zephyr Python requirements, then runs an initial West build.
+
+Example:
+
+```sh
+neoecu init
+```
+
+### `neoecu clean`
+
+Removes generated build directories for the configured cores while protecting the project root and configured source directories.
+
+Example:
+
+```sh
+neoecu clean
+```
+
+### `neoecu envcheck`
+
+Checks whether expected build tools, Zephyr environment variables, and Arm toolchain dependencies are available.
+
+Example:
+
+```sh
+neoecu envcheck
+```
diff --git a/pyproject.toml b/pyproject.toml
index 2a0967a..2a6ec63 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "neoecu"
-version = "2.0.0"
+version = "2.1.0"
 description = "NeoECU build and flash tooling"
 authors = [{ name = "Hector van der Aa", email = "hector@h3cx.dev" }]
 readme = "README.md"
diff --git a/src/neoecu/cli.py b/src/neoecu/cli.py
index f7c2e64..1fc8992 100644
--- a/src/neoecu/cli.py
+++ b/src/neoecu/cli.py
@@ -12,7 +12,7 @@ def main():
     subparsers = parser.add_subparsers(dest="command")
 
     build_parser = subparsers.add_parser("build")
-    subparsers.add_parser("flash")
+    flash_parser = subparsers.add_parser("flash")
     subparsers.add_parser("envcheck")
     subparsers.add_parser("init")
     subparsers.add_parser("clean")
@@ -20,6 +20,10 @@ def main():
     build_parser.add_argument("--debug", action="store_true")
     build_parser.add_argument("--release", action="store_true")
     build_parser.add_argument("--clean", action="store_true")
+    build_parser.add_argument("--CM7", action="store_true", help="Build only the CM7 core")
+    build_parser.add_argument("--CM4", action="store_true", help="Build only the CM4 core")
+    flash_parser.add_argument("--CM7", action="store_true", help="Flash only the CM7 core")
+    flash_parser.add_argument("--CM4", action="store_true", help="Flash only the CM4 core")
 
     args = parser.parse_args()
 
@@ -33,7 +37,7 @@ def main():
 
     pair = neoecu.common.check_pair(config)
     if not pair:
-        print("neoecu currently only support building ST for M7 and Zephyr for M4, update your neoecu.toml")
+        print("neoecu supports ST for CM7 and Zephyr for CM4. Configure at least one supported core in neoecu.toml")
         sys.exit(1)
 
     if args.command == "build":
@@ -41,7 +45,7 @@ def main():
         run(project_root, args)
     elif args.command == "flash":
         from .commands.flash import run 
-        run(project_root)
+        run(project_root, args)
     elif args.command == "envcheck":
         from .commands.envcheck import run 
         run()
diff --git a/src/neoecu/commands/build.py b/src/neoecu/commands/build.py
index e4031de..9a29262 100644
--- a/src/neoecu/commands/build.py
+++ b/src/neoecu/commands/build.py
@@ -48,9 +48,11 @@ def run(root_path: Path, args):
     print("Building NeoECU...")
 
     config = neoecu.common.load_config(root_path)
-
-    m7_root = root_path / config["build"]["m7_dir"]
-    m4_root = root_path / config["build"]["m4_dir"]
+    try:
+        cores = neoecu.common.select_cores(config, args)
+    except ValueError as exc:
+        print(exc)
+        sys.exit(1)
 
     # Validate mode
     if args.debug and args.release:
@@ -59,12 +61,13 @@ def run(root_path: Path, args):
 
     mode = "Debug" if args.debug else "Release"
 
-    # Ensure M7 initialized
-    m7_build_dir = m7_root / "build"
-    if not m7_build_dir.exists():
-        if not init_m7(m7_root):
-            print("Failed to init STM32 project")
-            sys.exit(1)
+    if "CM7" in cores:
+        m7_root = neoecu.common.core_root(root_path, config, "CM7")
+        m7_build_dir = m7_root / "build"
+        if not m7_build_dir.exists():
+            if not init_m7(m7_root):
+                print("Failed to init STM32 project")
+                sys.exit(1)
 
     table = Table()
     table.add_column("Step")
@@ -75,15 +78,17 @@ def run(root_path: Path, args):
 
     results: list[bool] = []
 
-    # M7 build
-    m7_ok = build_m7(m7_root, mode, args.clean)
-    table.add_row(f"M7 {mode}", ok_str if m7_ok else fail_str)
-    results.append(m7_ok)
+    if "CM7" in cores:
+        m7_root = neoecu.common.core_root(root_path, config, "CM7")
+        m7_ok = build_m7(m7_root, mode, args.clean)
+        table.add_row(f"CM7 {mode}", ok_str if m7_ok else fail_str)
+        results.append(m7_ok)
 
-    # M4 build
-    m4_ok = build_m4(m4_root, args.clean)
-    table.add_row("M4 build", ok_str if m4_ok else fail_str)
-    results.append(m4_ok)
+    if "CM4" in cores:
+        m4_root = neoecu.common.core_root(root_path, config, "CM4")
+        m4_ok = build_m4(m4_root, args.clean)
+        table.add_row("CM4 build", ok_str if m4_ok else fail_str)
+        results.append(m4_ok)
 
     console.print(table)
 
diff --git a/src/neoecu/commands/clean.py b/src/neoecu/commands/clean.py
index aee1f68..65240de 100644
--- a/src/neoecu/commands/clean.py
+++ b/src/neoecu/commands/clean.py
@@ -52,28 +52,26 @@ def run(root_path: Path):
     console = Console()
 
     config = neoecu.common.load_config(root_path)
-
-    m7_root = root_path / config["build"]["m7_dir"]
-    m4_root = root_path / config["build"]["m4_dir"]
+    cores = neoecu.common.configured_cores(config)
 
     # Build directories
-    m7_root_build_dir = m7_root / "build"
-    m7_cm7_build_dir = m7_root / "CM7" / "build"
-    m7_cm4_build_dir = m7_root / "CM4" / "build"
-    m4_root_build_dir = m4_root / "build"
+    build_dirs = []
 
-    build_dirs = [
-        ("M7 root build", m7_root_build_dir),
-        ("M7 CM7 build", m7_cm7_build_dir),
-        ("M7 CM4 build", m7_cm4_build_dir),
-        ("M4 root build", m4_root_build_dir),
-    ]
+    protected = [root_path]
 
-    protected = [
-        root_path,
-        m7_root,
-        m4_root,
-    ]
+    if "CM7" in cores:
+        m7_root = neoecu.common.core_root(root_path, config, "CM7")
+        protected.append(m7_root)
+        build_dirs.extend([
+            ("M7 root build", m7_root / "build"),
+            ("M7 CM7 build", m7_root / "CM7" / "build"),
+            ("M7 CM4 build", m7_root / "CM4" / "build"),
+        ])
+
+    if "CM4" in cores:
+        m4_root = neoecu.common.core_root(root_path, config, "CM4")
+        protected.append(m4_root)
+        build_dirs.append(("M4 root build", m4_root / "build"))
 
     table = Table()
     table.add_column("Directory")
diff --git a/src/neoecu/commands/flash.py b/src/neoecu/commands/flash.py
index 8c57538..fef705b 100644
--- a/src/neoecu/commands/flash.py
+++ b/src/neoecu/commands/flash.py
@@ -5,6 +5,8 @@
 from pathlib import Path
 import neoecu.common
 import subprocess
+import sys
+
 
 def gen_flash_script(jlink_path: Path, core: str, bin_path: Path) -> Path:
     jlink_path.mkdir(parents=True, exist_ok=True)
@@ -29,51 +31,42 @@ def gen_flash_script(jlink_path: Path, core: str, bin_path: Path) -> Path:
     new_script += "g\n"
     new_script += "exit"
 
-    script_path.write_text(new_script);
+    script_path.write_text(new_script)
     return script_path
 
 
+def find_single_elf(build_path: Path, pattern: str, core: str) -> Path:
+    matches = list(build_path.glob(pattern))
+
+    if not matches:
+        raise FileNotFoundError(f"No {pattern} found in {core} build directory")
+
+    if len(matches) > 1:
+        raise RuntimeError(f"Multiple {core} ELF files found: {matches}")
+
+    return matches[0]
 
 
-def run(root_path: Path):
-
+def run(root_path: Path, args):
     config = neoecu.common.load_config(root_path)
+    try:
+        cores = neoecu.common.select_cores(config, args)
+    except ValueError as exc:
+        print(exc)
+        sys.exit(1)
 
-    m7_root = root_path / config["build"]["m7_dir"]
-    m4_root = root_path / config["build"]["m4_dir"]
-
-    m7_jlink_scripts = m7_root / ".jlink_scripts"
-    m4_jlink_scripts = m4_root / ".jlink_scripts"
-
-    m7_build = m7_root / "CM7" / "build"
-
-    matches = list(m7_build.glob("*_CM7.elf"))
-
-    if not matches:
-        raise FileNotFoundError("No *_CM7.elf found in build directory")
-
-    if len(matches) > 1:
-        raise RuntimeError(f"Multiple CM7 ELF files found: {matches}")
-
-    m7_bin = matches[0]
-
-    m4_build = m4_root / "build" / "zephyr"
-
-    matches = list(m4_build.glob("zephyr.elf"))
-
-    if not matches:
-        raise FileNotFoundError("No *_CM4.elf found in build directory")
-
-    if len(matches) > 1:
-        raise RuntimeError(f"Multiple CM4 ELF files found: {matches}")
-
-    m4_bin = matches[0]
-
-    m7_flash_script = gen_flash_script(m7_jlink_scripts, "CM7", m7_bin)
-    m4_flash_script = gen_flash_script(m4_jlink_scripts, "CM4", m4_bin)
-    
-    subprocess.run(["JLinkExe", "-CommanderScript", f"{m4_flash_script}"], cwd=m4_root)
-    subprocess.run(["JLinkExe", "-CommanderScript", f"{m7_flash_script}"], cwd=m7_root)
-    
-    
+    if "CM4" in cores:
+        m4_root = neoecu.common.core_root(root_path, config, "CM4")
+        m4_jlink_scripts = m4_root / ".jlink_scripts"
+        m4_build = m4_root / "build" / "zephyr"
+        m4_bin = find_single_elf(m4_build, "zephyr.elf", "CM4")
+        m4_flash_script = gen_flash_script(m4_jlink_scripts, "CM4", m4_bin)
+        subprocess.run(["JLinkExe", "-CommanderScript", f"{m4_flash_script}"], cwd=m4_root)
 
+    if "CM7" in cores:
+        m7_root = neoecu.common.core_root(root_path, config, "CM7")
+        m7_jlink_scripts = m7_root / ".jlink_scripts"
+        m7_build = m7_root / "CM7" / "build"
+        m7_bin = find_single_elf(m7_build, "*_CM7.elf", "CM7")
+        m7_flash_script = gen_flash_script(m7_jlink_scripts, "CM7", m7_bin)
+        subprocess.run(["JLinkExe", "-CommanderScript", f"{m7_flash_script}"], cwd=m7_root)
diff --git a/src/neoecu/commands/init.py b/src/neoecu/commands/init.py
index d3564cc..92f600a 100644
--- a/src/neoecu/commands/init.py
+++ b/src/neoecu/commands/init.py
@@ -10,8 +10,7 @@ from pathlib import Path
 from rich.table import Table
 from rich.console import Console
 
-from neoecu.commands import build
-from neoecu.common import load_config
+import neoecu.common
 
 
 def get_env(var: str) -> str | None:
@@ -36,49 +35,53 @@ def run(root_path: Path):
     table.add_column("Status")
 
     results: list[bool] = []
+    config = neoecu.common.load_config(root_path)
+    cores = neoecu.common.configured_cores(config)
 
-    # Step 1 — Install west
-    west_ok = run_cmd(["uv", "pip", "install", "west"])
-    table.add_row("Install west", ok_str if west_ok else fail_str)
-    results.append(west_ok)
+    if "CM4" in cores:
+        # Step 1 — Install west
+        west_ok = run_cmd(["uv", "pip", "install", "west"])
+        table.add_row("Install west", ok_str if west_ok else fail_str)
+        results.append(west_ok)
 
-    # Step 2 — Zephyr requirements
-    requirements = get_env("ZEPHYR_BASE")
-    if requirements is None:
-        table.add_row("Zephyr requirements", "[red]ZEPHYR_BASE not set[/red]")
-        console.print(table)
-        sys.exit(1)
+        # Step 2 — Zephyr requirements
+        requirements = get_env("ZEPHYR_BASE")
+        if requirements is None:
+            table.add_row("Zephyr requirements", "[red]ZEPHYR_BASE not set[/red]")
+            console.print(table)
+            sys.exit(1)
 
-    requirements_path = Path(requirements) / "scripts" / "requirements.txt"
+        requirements_path = Path(requirements) / "scripts" / "requirements.txt"
 
-    deps_ok = run_cmd(["uv", "pip", "install", "-r", str(requirements_path)])
-    table.add_row("Install Zephyr deps", ok_str if deps_ok else fail_str)
-    results.append(deps_ok)
+        deps_ok = run_cmd(["uv", "pip", "install", "-r", str(requirements_path)])
+        table.add_row("Install Zephyr deps", ok_str if deps_ok else fail_str)
+        results.append(deps_ok)
 
-    # Step 3 — Load config
-    config = load_config(root_path)
-    m7_root = root_path / config["build"]["m7_dir"]
-    m4_root = root_path / config["build"]["m4_dir"]
+    if "CM7" in cores:
+        m7_root = neoecu.common.core_root(root_path, config, "CM7")
 
-    # Step 4 — CMake Debug Init
-    debug_ok = run_cmd(["cmake", "--preset", "Debug"], cwd=m7_root)
-    table.add_row("CMake Debug Init", ok_str if debug_ok else fail_str)
-    results.append(debug_ok)
+        # Step 4 — CMake Debug Init
+        debug_ok = run_cmd(["cmake", "--preset", "Debug"], cwd=m7_root)
+        table.add_row("CMake Debug Init", ok_str if debug_ok else fail_str)
+        results.append(debug_ok)
 
-    # Step 5 — CMake Release Init
-    release_ok = run_cmd(["cmake", "--preset", "Release"], cwd=m7_root)
-    table.add_row("CMake Release Init", ok_str if release_ok else fail_str)
-    results.append(release_ok)
+        # Step 5 — CMake Release Init
+        release_ok = run_cmd(["cmake", "--preset", "Release"], cwd=m7_root)
+        table.add_row("CMake Release Init", ok_str if release_ok else fail_str)
+        results.append(release_ok)
 
-    # Step 6 - CMake Debug Build
-    build_ok = run_cmd(["cmake", "--build", "--preset", "Debug", "--clean-first", "--verbose"], cwd=m7_root)
-    table.add_row("CMake Debug Build", ok_str if build_ok else fail_str)
-    results.append(build_ok)
+        # Step 6 - CMake Debug Build
+        build_ok = run_cmd(["cmake", "--build", "--preset", "Debug", "--clean-first", "--verbose"], cwd=m7_root)
+        table.add_row("CMake Debug Build", ok_str if build_ok else fail_str)
+        results.append(build_ok)
 
-    # Step 7 - Zephyr Debug
-    zephyr_ok = run_cmd(["west", "build","-p", "always", "-b", "arduino_giga_r1/stm32h747xx/m4"], cwd=m4_root)
-    table.add_row("Zephyr Build", ok_str if zephyr_ok else fail_str)
-    results.append(zephyr_ok)
+    if "CM4" in cores:
+        m4_root = neoecu.common.core_root(root_path, config, "CM4")
+
+        # Step 7 - Zephyr Debug
+        zephyr_ok = run_cmd(["west", "build", "-p", "always", "-b", "arduino_giga_r1/stm32h747xx/m4"], cwd=m4_root)
+        table.add_row("Zephyr Build", ok_str if zephyr_ok else fail_str)
+        results.append(zephyr_ok)
 
     # Print results table
     console.print(table)
diff --git a/src/neoecu/common.py b/src/neoecu/common.py
index 03fe129..f07fd54 100644
--- a/src/neoecu/common.py
+++ b/src/neoecu/common.py
@@ -4,6 +4,20 @@
 from pathlib import Path
 import tomllib
 
+CORE_CONFIG = {
+    "CM7": {
+        "dir_key": "m7_dir",
+        "type_key": "m7_type",
+        "supported_type": "ST",
+    },
+    "CM4": {
+        "dir_key": "m4_dir",
+        "type_key": "m4_type",
+        "supported_type": "Zephyr",
+    },
+}
+
+
 def find_project_root(
     start: Path | None = None,
     filename: str = "neoecu.toml",
@@ -27,7 +41,52 @@ def load_config(root: Path) -> dict:
     with open(config_path, "rb") as f:
         return tomllib.load(f) 
 
+
+def configured_cores(config: dict) -> list[str]:
+    build_config = config.get("build", {})
+    cores: list[str] = []
+
+    for core, core_config in CORE_CONFIG.items():
+        if all(build_config.get(key) for key in (core_config["dir_key"], core_config["type_key"])):
+            cores.append(core)
+
+    return cores
+
+
+def core_root(root: Path, config: dict, core: str) -> Path:
+    return root / config["build"][CORE_CONFIG[core]["dir_key"]]
+
+
+def select_cores(config: dict, args) -> list[str]:
+    selected = []
+
+    if getattr(args, "CM7", False):
+        selected.append("CM7")
+    if getattr(args, "CM4", False):
+        selected.append("CM4")
+
+    if not selected:
+        selected = configured_cores(config)
+
+    configured = configured_cores(config)
+    missing = [core for core in selected if core not in configured]
+    if missing:
+        missing_cores = ", ".join(missing)
+        raise ValueError(f"{missing_cores} is not fully configured in neoecu.toml")
+
+    return selected
+
+
 def check_pair(config: dict) -> bool:
-    if (config["build"]["m7_type"] == "ST") & (config["build"]["m4_type"] == "Zephyr"):
-        return True 
-    return False 
+    build_config = config.get("build", {})
+    cores = configured_cores(config)
+
+    if not cores:
+        return False
+
+    for core in cores:
+        core_config = CORE_CONFIG[core]
+        if build_config[core_config["type_key"]] != core_config["supported_type"]:
+            return False
+
+    return True
diff --git a/uv.lock b/uv.lock
index ae4b64f..ecb38eb 100644
--- a/uv.lock
+++ b/uv.lock
@@ -25,7 +25,7 @@ wheels = [
 
 [[package]]
 name = "neoecu"
-version = "0.1.0"
+version = "2.1.0"
 source = { editable = "." }
 dependencies = [
     { name = "rich" },