Bypass pyusb Device I/O on WinUSB with direct libusb bulk transfers

Device.write/read always call get_configuration which WinUSB does not
implement. Route all framed I/O through the backend with IF5 claimed.

Co-authored-by: Cursor <cursoragent@cursor.com>

juc500_xfer/protocol.py

@@ -193,7 +193,12 @@ class Session:
             try:
                 self.send(MsgType.HELLO, self.peer_name.encode("utf-8"))
             except Exception as exc:
-                self.log(f"HELLO 재전송 실패: {exc}")
+                # Peer not reading yet (FIFO full) → USB timeout; keep retrying quietly.
+                msg = str(exc)
+                if "timed out" in msg.lower() or "timeout" in msg.lower():
+                    self.log("상대 수신 대기 중… (HELLO)")
+                else:
+                    self.log(f"HELLO 재전송 실패: {exc}")
             self._connected.wait(timeout=min(2.0, remaining))
         return self._peer_hello or "peer"
 

juc500_xfer/usb_link.py

@@ -6,6 +6,7 @@ Device: VID 0x0711 / PID 0x7500 (product "Smart Data Link"), composite:
 
 from __future__ import annotations
 
+import array
 import os
 import subprocess
 import sys
@@ -432,55 +433,93 @@ class Juc500Link:
                 "JUC500(Smart Data Link / 0711:7500) 장치를 찾지 못했습니다.\n" + hints
             )
 
-        chosen = None
+        candidates = matches
-        for dev in matches:
+        if self._serial:
-            if self._serial:
+            candidates = [
-                s = _safe_str(dev, getattr(dev, "iSerialNumber", 0))
+                d
-                if s != self._serial.strip():
+                for d in matches
-                    continue
+                if _safe_str(d, getattr(d, "iSerialNumber", 0)) == self._serial.strip()
-            chosen = dev
+            ]
-            break
+            if not candidates:
-        if chosen is None:
+                raise RuntimeError(f"시리얼 '{self._serial}' 에 해당하는 JUC500 이 없습니다.")
-            raise RuntimeError(f"시리얼 '{self._serial}' 에 해당하는 JUC500 이 없습니다.")
 
+        self._dev = None
+        last_err: Exception | None = None
+        for chosen in candidates:
+            try:
+                self._try_open_device(chosen)
+                break
+            except Exception as exc:  # noqa: BLE001
+                last_err = exc
+                self._force_close()
+        else:
+            detail = f"\n마지막 오류: {last_err}" if last_err else ""
+            raise RuntimeError(
+                "JUC500 USB Interface 5 를 열 수 없습니다." + detail
+            ) from last_err
+
+        # Optional CDC — ignore failures (WinUSB often only on IF5)
+        self._claim(IF_CDC_DATA, required=False)
+        self._claim(IF_CDC_COMM, required=False)
+
+    def _try_open_device(self, chosen: usb.core.Device) -> None:
         self._dev = chosen
-
+        self._claimed = []
         if _IS_WIN:
             self._configure_windows()
         else:
             self._configure_posix()
-
         self._claim(IF_VENDOR, required=True)
-        self._claim(IF_CDC_DATA, required=False)
+        # Force backend path readiness (no Device.write get_configuration)
-        self._claim(IF_CDC_COMM, required=False)
+        self._ensure_backend_ready()
+
+    def _force_close(self) -> None:
+        try:
+            self.close()
+        except Exception:
+            pass
+        self._dev = None
+        self._claimed = []
 
     def _configure_windows(self) -> None:
-        """Avoid libusb_get_configuration — unimplemented on WinUSB.
+        """WinUSB: never call get_configuration / prefer skipping set_configuration.
 
-        Every pyusb read/write resolves endpoints via get_active_configuration(),
+        pyusb Device.read/write resolve endpoints via get_active_configuration(),
-        which calls backend.get_configuration() when the cache is empty and then
+        which calls libusb_get_configuration() — NOT_SUPPORTED on WinUSB.
-        raises 'Operation not supported or unimplemented on this platform'.
+        We seed caches and perform all bulk I/O through the backend directly.
-        Always seed _active_cfg_index after open.
         """
         assert self._dev is not None
+        # set_configuration is frequently NOT_SUPPORTED when the composite is
+        # already configured by Windows — skip rather than confuse WinUSB.
         try:
-            self._dev.set_configuration(1)
+            self._dev._ctx.managed_open()
-        except (usb.core.USBError, NotImplementedError):
+        except Exception:
             pass
         self._ensure_cfg_cache(force=True)
 
     def _ensure_cfg_cache(self, *, force: bool = False) -> None:
-        """Seed pyusb config index so I/O never calls get_configuration on WinUSB."""
+        """Seed pyusb config index so leftover Device.* paths skip get_configuration."""
         if self._dev is None:
             return
         try:
             ctx = self._dev._ctx
             if force or getattr(ctx, "_active_cfg_index", None) is None:
-                # Composite JUC500 exposes a single configuration at index 0.
                 ctx._active_cfg_index = 0
         except Exception:
             pass
 
+    def _ensure_backend_ready(self) -> None:
+        assert self._dev is not None
+        ctx = self._dev._ctx
+        with ctx.lock:
+            handle = ctx.managed_open()
+            if IF_VENDOR not in ctx._claimed_intf:
+                ctx.backend.claim_interface(handle, IF_VENDOR)
+                ctx._claimed_intf.add(IF_VENDOR)
+            if IF_VENDOR not in self._claimed:
+                self._claimed.append(IF_VENDOR)
+        self._ensure_cfg_cache(force=True)
+
     def _configure_posix(self) -> None:
         assert self._dev is not None
         try:
@@ -543,46 +582,36 @@ class Juc500Link:
         return self._bulk_read(EP_CTRL_IN, size, timeout_ms)
 
     def _bulk_write(self, ep: int, payload: bytes, timeout_ms: Optional[int]) -> int:
+        """Bulk OUT via libusb backend (skips pyusb get_configuration on WinUSB)."""
         assert self._dev is not None
-        if _IS_WIN:
-            self._ensure_cfg_cache()
         to = self.timeout_ms if timeout_ms is None else timeout_ms
         sent = 0
         view = memoryview(payload)
         while sent < len(payload):
-            chunk = view[sent : sent + MAX_PACKET]
+            chunk = bytes(view[sent : sent + MAX_PACKET])
             try:
-                n = self._dev.write(ep, chunk.tobytes(), timeout=to)
+                n = self._backend_bulk_write(ep, chunk, to)
+            except usb.core.USBTimeoutError:
+                raise
             except usb.core.USBError as exc:
-                if _IS_WIN and _is_not_supported(exc):
+                if _is_not_supported(exc):
-                    self._ensure_cfg_cache(force=True)
-                    try:
-                        n = self._dev.write(ep, chunk.tobytes(), timeout=to)
-                    except usb.core.USBError as exc2:
-                        raise RuntimeError(
-                            f"USB 쓰기 실패(EP 0x{ep:02x}): {exc2}\n"
-                            "Windows: Interface 5에 WinUSB가 잡혀 있는지 Zadig로 확인하세요."
-                        ) from exc2
-                elif _is_not_supported(exc):
                     raise RuntimeError(
                         f"USB 쓰기 실패(EP 0x{ep:02x}): {exc}\n"
-                        "Windows: Interface 5에 WinUSB가 잡혀 있는지 Zadig로 확인하세요."
+                        "Windows: Interface 5(MI_05)에 WinUSB가 잡혀 있는지 Zadig로 확인하세요.\n"
+                        "최신 dist-windows 빌드인지, 공식 Wormhole가 종료됐는지도 확인하세요."
                     ) from exc
-                else:
+                raise
-                    raise
+            sent += int(n)
-            sent += n
             if n == 0:
                 break
         return sent
 
     def _bulk_read(self, ep: int, size: int, timeout_ms: Optional[int]) -> bytes:
+        """Bulk IN via libusb backend (skips pyusb get_configuration on WinUSB)."""
         assert self._dev is not None
-        if _IS_WIN:
-            self._ensure_cfg_cache()
         to = self.timeout_ms if timeout_ms is None else timeout_ms
         try:
-            data = self._dev.read(ep, size, timeout=to)
+            return self._backend_bulk_read(ep, size, to)
-            return bytes(data)
         except usb.core.USBTimeoutError:
             return b""
         except usb.core.USBError as exc:
@@ -591,8 +620,7 @@ class Juc500Link:
                     if bigger <= size:
                         continue
                     try:
-                        data = self._dev.read(ep, bigger, timeout=to)
+                        return self._backend_bulk_read(ep, bigger, to)
-                        return bytes(data)
                     except usb.core.USBTimeoutError:
                         return b""
                     except usb.core.USBError as exc2:
@@ -600,28 +628,44 @@ class Juc500Link:
                             size = bigger
                             continue
                         if _is_not_supported(exc2):
-                            break
+                            raise RuntimeError(
+                                f"USB 읽기 실패(EP 0x{ep:02x}): {exc2}\n"
+                                "Windows: Interface 5에 WinUSB가 잡혀 있는지 Zadig로 확인하세요."
+                            ) from exc2
                         return b""
                 return b""
             if _is_not_supported(exc):
-                if _IS_WIN:
-                    self._ensure_cfg_cache(force=True)
-                    try:
-                        data = self._dev.read(ep, size, timeout=to)
-                        return bytes(data)
-                    except usb.core.USBTimeoutError:
-                        return b""
-                    except usb.core.USBError as exc2:
-                        raise RuntimeError(
-                            f"USB 읽기 실패(EP 0x{ep:02x}): {exc2}\n"
-                            "Windows: Interface 5에 WinUSB가 잡혀 있는지 Zadig로 확인하세요."
-                        ) from exc2
                 raise RuntimeError(
                     f"USB 읽기 실패(EP 0x{ep:02x}): {exc}\n"
                     "Windows: Interface 5에 WinUSB가 잡혀 있는지 Zadig로 확인하세요."
                 ) from exc
             return b""
 
+    def _backend_bulk_write(self, ep: int, data: bytes, timeout_ms: int) -> int:
+        assert self._dev is not None
+        ctx = self._dev._ctx
+        with ctx.lock:
+            handle = ctx.managed_open()
+            if IF_VENDOR not in ctx._claimed_intf:
+                ctx.backend.claim_interface(handle, IF_VENDOR)
+                ctx._claimed_intf.add(IF_VENDOR)
+            buff = array.array("B", data)
+            return int(ctx.backend.bulk_write(handle, ep, IF_VENDOR, buff, timeout_ms))
+
+    def _backend_bulk_read(self, ep: int, size: int, timeout_ms: int) -> bytes:
+        assert self._dev is not None
+        ctx = self._dev._ctx
+        with ctx.lock:
+            handle = ctx.managed_open()
+            if IF_VENDOR not in ctx._claimed_intf:
+                ctx.backend.claim_interface(handle, IF_VENDOR)
+                ctx._claimed_intf.add(IF_VENDOR)
+            buff = usb.util.create_buffer(size)
+            n = int(ctx.backend.bulk_read(handle, ep, IF_VENDOR, buff, timeout_ms))
+            if n <= 0:
+                return b""
+            return bytes(buff[:n])
+
     def drain(self, duration_s: float = 0.2) -> None:
         deadline = time.monotonic() + duration_s
         while time.monotonic() < deadline:

packaging/windows/README-WIN.txt

@@ -12,7 +12,9 @@ JUC500 — Windows 11 사용 안내
 5) Mac 쪽에서도 같은 프로그램을 실행한 뒤 연결합니다.
 
 오류 "Operation not supported or unimplemented on this platform"
-  → 구버전 버그이거나 Interface 5 WinUSB 미설치. 최신 Setup/portable 로 업데이트하고
+  → pyusb가 WinUSB에서 get_configuration 을 호출할 때 발생합니다.
-    Zadig에서 Interface 5 가 WinUSB 인지 다시 확인하세요.
+    2026-07-15 이후 빌드(backend 직접 전송)로 교체하세요.
+    그래도 같으면 Zadig에서 Interface 5(MI_05) = WinUSB 인지 확인하고
+    케이블을 뽑았다 다시 꽂은 뒤 JUC500 을 재실행하세요.
 
 포터블: JUC500-portable.exe 는 설치 없이 실행할 수 있습니다.