Of course! Working with USB devices in Python on Windows is a common task, but it requires the right tools and understanding. Here’s a comprehensive guide covering the concepts, libraries, and a step-by-step example.

Core Concepts on Windows

On Windows, USB devices are managed by the Windows Driver Framework (WDF). Directly communicating with a USB device from a user-mode application (like a Python script) requires going through the operating system's USB stack. This is different from Linux, where you often have direct access to device files like /dev/ttyACM0.

The key components are:

1. VID (Vendor ID) and PID (Product ID): Every USB device has a unique 16-bit Vendor ID and 16-bit Product ID. These are the primary ways to identify which device you want to talk to.
2. Device Interface: When a USB driver is installed for a device, it creates a "device interface" in the Windows Registry. Your application finds this interface to get a handle for communication.
3. Handle: Once you have a handle to the device interface, you can use Windows API functions (like CreateFile, DeviceIoControl, WriteFile, ReadFile) to send and receive data.

Recommended Python Libraries

You don't need to write raw C-style API calls. Several excellent Python libraries wrap this complexity for you.

pyusb (The Standard Choice)

pyusb is a pure Python wrapper around the libusb library. It's powerful, cross-platform (works on Windows, Linux, macOS), and gives you low-level control. This is often the best place to start.

How it works on Windows: pyusb needs a way to talk to the USB stack on Windows. It does this by using a userspace driver library, most commonly libusb-win32 (which provides a backend called libusb1). You need to install this driver for your specific device or for all USB devices.

Installation:

pip install pyusb

Prerequisite (The Crucial Step on Windows): You need to install the libusb-win32 filter driver. The easiest way is to use Zadig.

1. Download Zadig: Get it from the official GitHub releases page.
2. Run Zadig: Plug in your USB device.
3. Select your Device: In Zadig, from the "List all devices" dropdown, select your USB device.
4. Install the Driver: In the "Driver" dropdown, select libusb-win32 (v1.2.6.0). Click "Install Driver".
5. Done! Zadig will install the necessary driver, allowing pyusb to access the device.

pywinusb (Windows-Only, Easier Setup)

pywinusb is a library specifically for Windows. It uses the native Windows USB API, which means you do not need to install any external drivers like Zadig. This is a major advantage for beginners.

Installation:

pip install pywinusb

Step-by-Step Example with pywinusb

Let's walk through a complete example using pywinusb because it's simpler to set up on Windows. We will:

1. List all connected USB devices.
2. Find a specific device by its VID and PID.
3. Send data to it and receive data from it.

Scenario: Let's pretend we have a custom USB device with:

• VID: 0x0483 (STMicroelectronics, a common VID for dev boards)
• PID: 0x5740 (A fictional PID for our example device)
• Endpoint for sending data (OUT): 0x01
• Endpoint for receiving data (IN): 0x81

Step 1: Find Your Device's VID and PID

1. Plug in your USB device.
2. Open Device Manager (right-click the Start button and select "Device Manager").
3. Expand the "Universal Serial Bus controllers" section.
4. Find your device. It might be listed under "USB devices," "Ports (COM & LPT)," or with a specific driver name.
5. Right-click on it and select Properties.
6. Go to the Details tab.
7. From the "Property" dropdown, select Hardware Ids.
8. You will see a value like USB\VID_0483&PID_5740\.... The VID_0483 is the Vendor ID and PID_5740 is the Product ID.

Step 2: The Python Script

Create a Python file (e.g., usb_device_test.py) and use the following code.

import pywinusb.usb as usb
import time
# --- Configuration ---
# Replace with your device's actual VID and PID
TARGET_VID = 0x0483
TARGET_PID = 0x5740
# Endpoint addresses (1 for OUT, 81 for IN are common, check your device docs)
OUT_ENDPOINT_INDEX = 0  # Index of the OUT endpoint in the interface descriptor
IN_ENDPOINT_INDEX = 0    # Index of the IN endpoint
def device_found(dev):
    """Callback function called when a matching device is found."""
    print(f"Found device: {dev}")
    print(f"  - Vendor ID: 0x{dev.vendor_id:04X}")
    print(f"  - Product ID: 0x{dev.product_id:04X}")
    # We found our device, let's use it
    dev.set_configuration() # Must be called before claiming the interface
    print("Device configured. Claiming interface...")
    # Find the interface with the correct VID/PID
    # We assume the first interface is the one we want
    interface = dev.get_active_configuration()[0]
    # Find the IN and OUT endpoints
    out_ep = None
    in_ep = None
    for endpoint in interface:
        if endpoint.endpoint_address == 0x01: # OUT endpoint
            out_ep = endpoint
            print(f"  - Found OUT endpoint: {endpoint.endpoint_address}")
        elif endpoint.endpoint_address == 0x81: # IN endpoint
            in_ep = endpoint
            print(f"  - Found IN endpoint: {endpoint.endpoint_address}")
    if out_ep and in_ep:
        print("\n--- Communicating with device ---")
        try:
            # Send data to the device
            data_to_send = b"GET_STATUS\n" # Example command
            print(f"Sending: {data_to_send}")
            out_ep.write(data_to_send)
            # Read data from the device
            # read() is a blocking call, use a timeout or a separate thread
            # for non-blocking operation. Here we wait for 1 second.
            print("Waiting for response...")
            time.sleep(1) # Give the device time to process
            # We use a lambda to read data in a non-blocking way with a timeout
            # The actual read might need to be in a loop for continuous data
            data_read = in_ep.read(read_buffer_size=64, timeout=1000) # Read up to 64 bytes, 1s timeout
            print(f"Received: {data_read}")
        except usb.USBError as e:
            print(f"USB Error: {e}")
        finally:
            print("Releasing interface...")
            # Release the interface
            dev.release_interface()
    else:
        print("Could not find required IN/OUT endpoints.")
    print("--- Communication finished ---")
    # Stop the USB thread
    usb.core.find(find_all=True) # This will signal the backend to stop
def main():
    """Main function to find and connect to the USB device."""
    print("Searching for USB device...")
    # Find all devices matching our VID/PID
    devices = usb.core.find(find_all=True, idVendor=TARGET_VID, idProduct=TARGET_PID)
    if devices:
        # pywinusb returns a list, we'll just use the first one
        # The `find` function with a callback is more robust
        usb.core.find(custom_match=lambda d: d.vendor_id == TARGET_VID and d.product_id == TARGET_PID, callback=device_found)
    else:
        print(f"No device found with VID=0x{TARGET_VID:04X} and PID=0x{TARGET_PID:04X}")
if __name__ == '__main__':
    main()

Step 3: Run the Script

1. Make sure your USB device is plugged in.
2. Open Command Prompt or PowerShell.
3. Navigate to the directory where you saved your script.
4. Run the script: python usb_device_test.py

Expected Output:

Searching for USB device...
Found device: UsbDevice(Vendor: 0x0483, Product: 0x5740, Serial: None, Interface: (0, 0))
  - Vendor ID: 0x0483
  - Product ID: 0x5740
Device configured. Claiming interface...
  - Found OUT endpoint: 1
  - Found IN endpoint: 81
--- Communicating with device ---
Sending: b'GET_STATUS\n'
Waiting for response...
Received: b'Device OK: Temp=25C\n'
--- Communication finished ---

Troubleshooting Common Issues

• USBError: [Errno 13] Access is denied

  • Cause: This is the most common error. It means your script doesn't have permission to access the device.
  • Solution (for pyusb): You didn't install the libusb-win32 driver with Zadig.
  • Solution (for pywinusb): This is less common but can happen. Try running your script as an Administrator. Right-click your terminal or Python IDE and select "Run as administrator".

• No device found with VID=... and PID=...

  • Cause: The device isn't plugged in, the VID/PID is incorrect, or the driver isn't installed correctly.
  • Solution: Double-check the VID and PID in the Device Manager. If using pyusb, make sure you used Zadig to install the libusb-win32 driver.

• The script hangs on in_ep.read()

  • Cause: The read() function is blocking. If the device never sends data, it will wait forever.
  • Solution: Always use the timeout parameter in the read() method (as shown in the example). If you expect continuous data, you should put the read() call inside a while loop in a separate thread.

Summary: Which Library to Choose?