Route nRF52 framework diagnostics through USB logging policy

scripts/nrf52_loop_stack_fix.py

@@ -1,10 +1,14 @@
-"""Make the nRF52 core's loop task use the configured stack even under LTO.
+"""Apply MeshCore's loop-stack and diagnostic-output policy to the nRF52 core.
 
 GNU --wrap only redirects undefined references. The pinned core and FreeRTOS
 share an LTO graph, so its xTaskCreate call can bind directly to the real
 function and silently retain the framework's 4 KiB stack. Explicitly route
 only the core loop-task call through MeshCore's existing stack policy in a
-private build copy. Never edit the shared framework package.
+private build copy. Retarget the default framework printf logger through
+MeshCore's bounded, runtime-selected diagnostic stream: raw Serial writes
+otherwise corrupt the Companion protocol, including on dual-CDC hardware.
+Explicit UART/RTT loggers retain their framework behavior. Never edit the
+shared framework package.
 """
 
 from pathlib import Path
@@ -19,6 +23,34 @@ DECLARATION = """extern "C" BaseType_t __wrap_xTaskCreate(
 
 """
 LOOP_STACK = "#define LOOP_STACK_SZ       (256*4)"
+LOGGER_ENTRY = "// nanolib printf() retarget\n"
+LOGGER_DECLARATION = """// MeshCore routes default framework diagnostics without borrowing CDC0.
+size_t meshNrf52FrameworkDebugWrite(const void* data, size_t size)
+    __attribute__((weak));
+
+"""
+OLD_LOGGER = """#else
+  if ( Serial )
+  {
+    ret = Serial.write((const uint8_t *) buf, count);
+  }
+#endif
+
+  return (int) ret;
+"""
+LOGGER = """#else
+  if ( meshNrf52FrameworkDebugWrite )
+  {
+    ret = meshNrf52FrameworkDebugWrite(buf, count);
+  }
+  else if ( Serial )
+  {
+    ret = Serial.write((const uint8_t *) buf, count);
+  }
+#endif
+
+  return (int) ret;
+"""
 
 
 def patched_source(source):
@@ -36,14 +68,29 @@ def patched_source(source):
         OLD_LOOP_CREATE, LOOP_CREATE)
 
 
+def patched_logging_source(source):
+    source = source.replace("\r\n", "\n")
+    if (source.count(LOGGER) == 1 and source.count(LOGGER_DECLARATION) == 1
+            and OLD_LOGGER not in source and source.count(LOGGER_ENTRY) == 1):
+        return source
+    if (source.count(OLD_LOGGER) != 1 or source.count(LOGGER_ENTRY) != 1
+            or LOGGER in source or LOGGER_DECLARATION in source):
+        raise RuntimeError(
+            "nRF52 framework logging fix: unrecognized printf retarget; review "
+            "the framework update before building (shared SDK not modified)"
+        )
+    return source.replace(LOGGER_ENTRY, LOGGER_DECLARATION + LOGGER_ENTRY).replace(
+        OLD_LOGGER, LOGGER)
+
+
 def replace_core(build_env, node):
     source = Path(node.srcnode().get_abspath())
-    patched = patched_source(source.read_text(encoding="utf-8"))
+    patched = patched_logging_source(patched_source(source.read_text(encoding="utf-8")))
     destination = Path(build_env.subst("$BUILD_DIR")) / "patched-nrf52-core" / "main.cpp"
     destination.parent.mkdir(parents=True, exist_ok=True)
     if not destination.exists() or destination.read_text(encoding="utf-8") != patched:
         destination.write_text(patched, encoding="utf-8")
-    print("nRF52 loop stack: explicit LTO-safe core task policy enabled")
+    print("nRF52 core: LTO-safe loop stack and routed framework diagnostics enabled")
     return build_env.File(str(destination))