feat: LP-Core ULP support for Arduino-only projects

README.md

@@ -56,6 +56,28 @@ pio run -t download_fatfs # Download and extract FatFS from device
 
 See the [arduino-fatfs example](examples/arduino-fatfs/) for a complete working example.
 
+## LP-Core ULP Coprocessor Support
+
+pioarduino supports building LP-Core (Ultra Low Power) coprocessor programs directly from Arduino-only projects — no ESP-IDF CMake pipeline or custom build scripts required.
+
+**Supported MCUs:** ESP32-C5, ESP32-C6, ESP32-P4
+
+**Quick Start:**
+
+1. Create a `ulp/` directory in your project root with your LP-Core C or assembly sources.
+2. Build normally — the platform detects `ulp/` and compiles + embeds the ULP binary automatically.
+
+```ini
+[env:esp32c6]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/stable/platform-espressif32.zip
+framework = arduino
+board = esp32-c6-devkitc-1
+```
+
+The builder generates `ulp_main.h` (symbol map) and `ulp_main_bin.h` (binary declarations) in the build directory, available via `#include`. The first build triggers a one-time lib recompilation to enable ULP loader APIs. An optional `ulp/sdkconfig.h` can override the default ULP configuration (8 KB reserved memory).
+
+See the [arduino-ulp-blink](examples/arduino-ulp-blink/) example for a complete working project. For ESP-IDF or hybrid (arduino + espidf) projects, the existing CMake-based ULP pipeline is used instead — see [espidf-ulp-lp](examples/espidf-ulp-lp/) and [espidf-arduino-C6-ULP-blink](examples/espidf-arduino-C6-ULP-blink/).
+
 ### Stable Arduino
 currently espressif Arduino 3.3.7 and IDF v5.5.2+
 

builder/frameworks/arduino.py

@@ -555,6 +555,74 @@ def safe_remove_sdkconfig_files():
 if board_sdkconfig:
     flag_custom_sdkconfig = True
 
+# Auto-configure ULP support when ulp/ directory with sources is present on an
+# LP-Core MCU. Injects custom_sdkconfig entries to trigger lib recompilation
+# with ULP loader functions, and removes components that break the recompile.
+# Keep in sync with LP_CORE_MCUS and ULP_SOURCE_SUFFIXES in ulp_lp_core.py
+_lp_core_mcus = ("esp32c5", "esp32c6", "esp32p4")
+_ulp_source_suffixes = (".c", ".S", ".s")
+
+
+def _has_ulp_sources(ulp_dir):
+    """Check if a directory tree contains LP-Core source files."""
+    return ulp_dir.is_dir() and any(
+        f.suffix in _ulp_source_suffixes
+        for f in ulp_dir.rglob("*") if f.is_file()
+    )
+
+
+_ulp_dir = Path(project_dir) / "ulp"
+if mcu in _lp_core_mcus and _has_ulp_sources(_ulp_dir):
+    _ulp_sdkconfig_entries = [
+        "CONFIG_ULP_COPROC_ENABLED=y",
+        "CONFIG_ULP_COPROC_TYPE_LP_CORE=y",
+        # 8192 gives headroom beyond IDF's 4096 default. Users can
+        # override via custom_sdkconfig if they need more (or less).
+        "CONFIG_ULP_COPROC_RESERVE_MEM=8192",
+    ]
+    for entry in _ulp_sdkconfig_entries:
+        key = entry.split("=")[0]
+        if key not in entry_custom_sdkconfig:
+            entry_custom_sdkconfig += "\n" + entry
+    flag_custom_sdkconfig = True
+    config.set(current_env_section, "custom_sdkconfig",
+               entry_custom_sdkconfig)
+
+    # Components that fail the lib-recompile build on most pioarduino
+    # targets. If future IDF versions fix these, they can be removed.
+    _ulp_component_remove = [
+        "espressif/esp_insights",
+        "espressif/esp_rainmaker",
+        "espressif/rmaker_common",
+        "espressif/esp_diag_data_store",
+        "espressif/esp_diagnostics",
+    ]
+    existing_removes = env.GetProjectOption("custom_component_remove", "")
+    new_removes = []
+    for comp in _ulp_component_remove:
+        if comp not in existing_removes:
+            new_removes.append(comp)
+    if new_removes:
+        combined = existing_removes.strip()
+        if combined:
+            combined += "\n"
+        combined += "\n".join(new_removes)
+        config.set(current_env_section, "custom_component_remove", combined)
+    flag_custom_component_remove = True
+
+    _ulp_lib_ignore = ["RainMaker", "Insights"]
+    existing_ignores = env.GetProjectOption("lib_ignore", [])
+    if isinstance(existing_ignores, str):
+        existing_ignores = [existing_ignores]
+    new_ignores = [lib for lib in _ulp_lib_ignore
+                   if lib not in existing_ignores]
+    if new_ignores:
+        config.set(current_env_section, "lib_ignore",
+                   existing_ignores + new_ignores)
+    flag_lib_ignore = True
+
+    print("*** ULP auto-config: sdkconfig, component_remove, lib_ignore ***")
+
 extra_flags_raw = board.get("build.extra_flags", [])
 if isinstance(extra_flags_raw, list):
     extra_flags = " ".join(extra_flags_raw).replace("-D", " ")
@@ -568,8 +636,14 @@ def safe_remove_sdkconfig_files():
 
 SConscript("_embed_files.py", exports="env")
 
-flag_any_custom_sdkconfig = (FRAMEWORK_LIB_DIR is not None and 
-                            exists(str(Path(FRAMEWORK_LIB_DIR) / "sdkconfig")))
+# Check if libs were previously recompiled for THIS chip.  idf_lib_copy()
+# renames the stock sdkconfig to sdkconfig.orig during recompilation, so its
+# presence is a reliable per-chip indicator.  Using the chip-specific path
+# (instead of the root "sdkconfig") prevents cross-env flip-flopping: an env
+# for a different MCU won't see another chip's recompilation artefact and
+# trigger a spurious framework reinstall (check_reinstall_frwrk line 722).
+flag_any_custom_sdkconfig = (FRAMEWORK_LIB_DIR is not None and
+                            exists(str(Path(FRAMEWORK_LIB_DIR) / chip_variant / "sdkconfig.orig")))
 
 
 def has_unicore_flags():
@@ -996,3 +1070,7 @@ def custom_object_wrapper(_node, **kwargs):
 
     build_script_path = str(Path(FRAMEWORK_DIR) / "tools" / "pioarduino-build.py")
     SConscript(build_script_path)
+
+    # LP-Core ULP support for Arduino-only builds
+    if _has_ulp_sources(Path(env.subst("$PROJECT_DIR")) / "ulp"):
+        SConscript("ulp_lp_core.py", exports="env")

builder/frameworks/espidf.py

@@ -812,6 +812,12 @@ def HandleCOMPONENTsettings(env):
     if not bool(os.path.exists(str(Path(PROJECT_DIR) / ".dummy"))):
         shutil.copytree(LIB_SOURCE, str(Path(PROJECT_DIR) / ".dummy"))
     PROJECT_SRC_DIR = str(Path(PROJECT_DIR) / ".dummy")
+    # Save user's build_flags before clearing — PlatformIO core already
+    # parsed them into CPPDEFINES/CCFLAGS, and env.Replace() only clears
+    # the string variables, not the parsed effects.  Removing the user's
+    # build_flags prevents conflicts with CMake code model defines during
+    # lib recompilation (e.g. -DARDUINO_USB_CDC_ON_BOOT=0 vs =1).
+    _saved_build_flags = env.get("BUILD_FLAGS", "")
     env.Replace(
         PROJECT_SRC_DIR=PROJECT_SRC_DIR,
         BUILD_FLAGS="",
@@ -820,6 +826,10 @@ def HandleCOMPONENTsettings(env):
         PIOFRAMEWORK="arduino",
         ARDUINO_LIB_COMPILE_FLAG="Build",
     )
+    if _saved_build_flags:
+        env.ProcessUnFlags(
+            _saved_build_flags if isinstance(_saved_build_flags, str)
+            else " ".join(_saved_build_flags))
     env["INTEGRATION_EXTRA_DATA"].update({"arduino_lib_compile_flag": env.subst("$ARDUINO_LIB_COMPILE_FLAG")})
 
 def get_project_lib_includes(env):
@@ -2652,6 +2662,9 @@ def _replace_copy(src, dst):
 
         _replace_copy(str(Path(lib_dst) / "libspi_flash.a"), str(Path(mem_var) / "libspi_flash.a"))
         _replace_copy(str(Path(env_build) / "memory.ld"), str(Path(ld_dst) / "memory.ld"))
+        sections_ld = str(Path(env_build) / "sections.ld")
+        if os.path.isfile(sections_ld):
+            _replace_copy(sections_ld, str(Path(ld_dst) / "sections.ld"))
         if mcu == "esp32s3":
             _replace_copy(str(Path(lib_dst) / "libesp_psram.a"), str(Path(mem_var) / "libesp_psram.a"))
             _replace_copy(str(Path(lib_dst) / "libesp_system.a"), str(Path(mem_var) / "libesp_system.a"))
@@ -2664,7 +2677,10 @@ def _replace_copy(src, dst):
         if not bool(os.path.isfile(str(Path(arduino_libs) / chip_variant / "sdkconfig.orig"))):
             shutil.move(str(Path(arduino_libs) / chip_variant / "sdkconfig"), str(Path(arduino_libs) / chip_variant / "sdkconfig.orig"))
         shutil.copyfile(str(Path(env.subst("$PROJECT_DIR")) / ("sdkconfig." + env["PIOENV"])), str(Path(arduino_libs) / chip_variant / "sdkconfig"))
-        shutil.copyfile(str(Path(env.subst("$PROJECT_DIR")) / ("sdkconfig." + env["PIOENV"])), str(Path(arduino_libs) / "sdkconfig"))
+        # Note: intentionally NOT copying to the libs root (arduino_libs / "sdkconfig").
+        # The root copy caused cross-env flip-flopping: any env for a different MCU
+        # without custom_sdkconfig would see it, trigger check_reinstall_frwrk(),
+        # and reinstall the stock libs — wiping out this chip's recompiled artefacts.
         try:
             # clean env build folder to avoid issues with following Arduino build
             shutil.rmtree(env_build)