Bus Hound is a powerful software-based USB bus analyzer used to troubleshoot USB enumeration errors by capturing and analyzing the low-level communication between a USB host controller and a device. When a device fails enumeration—often appearing as an “Unknown USB Device (Device Descriptor Request Failed)” in Windows—Bus Hound helps determine if the issue is a failure in the initial handshake, a power issue, or incorrect device descriptor data. Here is how to use Bus Hound to troubleshoot these errors: 1. Preparation and Setup
Install Bus Hound: Install the software on the host computer.
Unplug Devices: To isolate the issue, start by unplugging all USB devices.
Launch Bus Hound: Open the program, which will display all connected USB controllers and hubs. 2. Capturing Enumeration Data
Select Device: In the Devices tab, identify the hub or port where the malfunctioning device will be plugged.
Capture Settings: Go to the Capture tab and ensure it is set to capture “USB” devices.
Plug in Device: Plug in the USB device that is failing enumeration. Run Capture: Click the Run button to begin logging data.
Analyze the Sequence: Look for the following sequence in the command log:
GET_DESCRIPTOR: Specifically, GET_DESCRIPTOR Request Device (asking for the device descriptor).
Failed Requests: A failed enumeration will often show a GET_DESCRIPTOR request followed by a STALL or an error code rather than the device data. 3. Interpreting Results
No Data Captured: If Bus Hound shows no traffic at all when the device is plugged in, it is likely a hardware failure, such as a broken connector or lack of power.
Request Failed (Descriptor Error): If the device responds with an error to GET_DESCRIPTOR, the device’s microcontroller or firmware is failing to properly identify itself, causing the “Device Descriptor Request Failed” error.
Incorrect Information: If data is returned, check if the Vendor ID (VID) and Product ID (PID) are correct, or if the data is scrambled. 4. Advanced Debugging (Firmware)
If you are developing the device, use the captured data to pinpoint which stage of the USB handshake failed:
Reset -> Set Address -> Get Descriptor -> Set Configuration.
A failure at “Set Address” usually indicates a failure in firmware handling, while a failure at “Get Descriptor” indicates incorrect descriptor structures.
By analyzing the specific point where the communication fails, Bus Hound allows you to differentiate between a physical connection failure and a firmware-level descriptor error.
If you can tell me the specific error code shown in Windows Device Manager (e.g., Code 43, Code 10), I can provide more specific troubleshooting steps for your situation. USB0 Enumeration error – Processors forum – TI E2E