From 9950bf7232d80f9195a0ab910d99952f0d192c37 Mon Sep 17 00:00:00 2001
From: jim800121chen <jim800121.chen@gmail.com>
Date: Mon, 9 Mar 2026 21:31:35 +0800
Subject: [PATCH] fix: add retry logic for KL520 USB connect and better error
 hints

- Retry connect up to 3 times with 2s delay and re-scan between attempts
- Re-scan refreshes USB device handles which can resolve timing issues
- Add Windows-specific hint about Zadig/WinUSB driver in error message
- Firmware reload reconnect also gets retry + fallback to without_check

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../server/scripts/kneron_bridge.py           | 81 ++++++++++++++-----
 1 file changed, 63 insertions(+), 18 deletions(-)

diff --git a/edge-ai-platform/server/scripts/kneron_bridge.py b/edge-ai-platform/server/scripts/kneron_bridge.py
index 90de33d..5638b1b 100644
--- a/edge-ai-platform/server/scripts/kneron_bridge.py
+++ b/edge-ai-platform/server/scripts/kneron_bridge.py
@@ -698,18 +698,48 @@ def handle_connect(params):
         # In these cases, connect_devices_without_check() works and we can
         # still load firmware afterwards.
         use_without_check = (_device_chip == "KL720") or (not target_dev.is_connectable)
-        if use_without_check:
-            _log(f"{_device_chip}: Using connect_devices_without_check(usb_port_id={target_dev.usb_port_id}, connectable={target_dev.is_connectable})...")
-            _device_group = kp.core.connect_devices_without_check(
-                usb_port_ids=[target_dev.usb_port_id]
-            )
-            _log(f"connect_devices_without_check succeeded")
-        else:
-            _log(f"Calling kp.core.connect_devices(usb_port_id={target_dev.usb_port_id})...")
-            _device_group = kp.core.connect_devices(
-                usb_port_ids=[target_dev.usb_port_id]
-            )
-            _log(f"connect_devices succeeded")
+
+        max_retries = 3
+        last_err = None
+        for attempt in range(max_retries):
+            try:
+                if use_without_check:
+                    _log(f"{_device_chip}: connect_devices_without_check(usb_port_id={target_dev.usb_port_id}, connectable={target_dev.is_connectable}) attempt {attempt+1}/{max_retries}...")
+                    _device_group = kp.core.connect_devices_without_check(
+                        usb_port_ids=[target_dev.usb_port_id]
+                    )
+                else:
+                    _log(f"connect_devices(usb_port_id={target_dev.usb_port_id}) attempt {attempt+1}/{max_retries}...")
+                    _device_group = kp.core.connect_devices(
+                        usb_port_ids=[target_dev.usb_port_id]
+                    )
+                _log(f"connect succeeded on attempt {attempt+1}")
+                last_err = None
+                break
+            except Exception as conn_err:
+                last_err = conn_err
+                _log(f"connect attempt {attempt+1} failed: {conn_err}")
+                if attempt < max_retries - 1:
+                    time.sleep(2)
+                    # Re-scan to refresh device handle
+                    try:
+                        descs = kp.core.scan_devices()
+                        for i in range(descs.device_descriptor_number):
+                            dev = descs.device_descriptor_list[i]
+                            if port and str(dev.usb_port_id) == port:
+                                target_dev = dev
+                                break
+                            elif not port:
+                                target_dev = descs.device_descriptor_list[0]
+                                break
+                    except Exception:
+                        pass
+
+        if last_err is not None:
+            hint = ""
+            if sys.platform == "win32":
+                hint = " On Windows, ensure the WinUSB driver is installed for this device (use Zadig: https://zadig.akeo.ie)."
+            raise RuntimeError(f"Failed to connect after {max_retries} attempts: {last_err}.{hint}")
 
         # KL720 needs longer timeout for large NEF transfers (12MB+ over USB)
         _timeout_ms = 60000 if _device_chip == "KL720" else 10000
@@ -732,12 +762,27 @@ def handle_connect(params):
                 _log("Firmware loaded, waiting for reboot...")
                 time.sleep(5)
 
-                # Reconnect after firmware load
-                descs = kp.core.scan_devices()
-                target_dev = descs.device_descriptor_list[0]
-                _device_group = kp.core.connect_devices(
-                    usb_port_ids=[target_dev.usb_port_id]
-                )
+                # Reconnect after firmware load (with retry)
+                _device_group = None
+                for retry in range(3):
+                    try:
+                        descs = kp.core.scan_devices()
+                        target_dev = descs.device_descriptor_list[0]
+                        try:
+                            _device_group = kp.core.connect_devices(
+                                usb_port_ids=[target_dev.usb_port_id]
+                            )
+                        except Exception:
+                            _device_group = kp.core.connect_devices_without_check(
+                                usb_port_ids=[target_dev.usb_port_id]
+                            )
+                        break
+                    except Exception as re_err:
+                        _log(f"Reconnect attempt {retry+1} failed: {re_err}")
+                        if retry < 2:
+                            time.sleep(3)
+                if _device_group is None:
+                    return {"error": "Device not found after firmware load. Unplug and re-plug the device."}
                 kp.core.set_timeout(
                     device_group=_device_group, milliseconds=_timeout_ms
                 )