First commit

esp32/scripts/no_stub.py

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+# Flash the ESP32-C3 with the ROM loader instead of esptool's RAM stub.
+#
+# Over the C3's native USB-Serial-JTAG the stub loads and starts, then the
+# transfer stalls with "Packet content transfer stopped (received 0 bytes)" —
+# reproducibly so through a USB hub. The ROM loader has no such trouble and is
+# no slower here, because the link runs at USB speed regardless of the nominal
+# baud rate.
+#
+# PlatformIO exposes --before/--after through board_upload.*, but not --no-stub,
+# so it gets spliced into the argument list ahead of the write_flash subcommand
+# (esptool requires global options to precede it).
+Import("env")
+
+flags = list(env.get("UPLOADERFLAGS", []))
+if "write_flash" in flags and "--no-stub" not in flags:
+    flags.insert(flags.index("write_flash"), "--no-stub")
+    env.Replace(UPLOADERFLAGS=flags)
+    print("no_stub.py: using the ROM loader (--no-stub) for upload")