micropython/usb/device/mtp: Add USB MTP class driver.

This adds a new driver implementing the USB MTP (Media Transfer Protocol)
class, allowing host computers to access the MicroPython
filesystem.

Signed-off-by: Andrew Leech <andrew@alelec.net>

Author: andrewleech

micropython/usb/README.md

@@ -134,3 +134,13 @@ USB MIDI devices in MicroPython.
 
 The example [midi_example.py](examples/device/midi_example.py) demonstrates how
 to create a simple MIDI device to send MIDI data to and from the USB host.
+
+### Package usb-device-mtp
+
+This package provides the `usb.device.mtp` module. This allows implementing
+USB MTP (Media Transfer Protocol) devices in MicroPython, exposing the MicroPython
+filesystem to a host computer for file operations.
+
+The example [mtp_example.py](examples/device/mtp_example.py) demonstrates how
+to create an MTP device that allows a host computer to browse, upload, download,
+and manipulate files on the MicroPython device.

micropython/usb/examples/device/mtp_example.py

@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: MIT
+# Copyright (c) 2023 MicroPython Team
+
+"""
+Example showing how to implement a USB MTP device to expose the MicroPython filesystem.
+
+This example uses the MicroPython USB MTP driver to expose the filesystem
+to a host computer as a Media Transfer Protocol (MTP) device. This allows
+the host to browse, download, upload, and manipulate files on the MicroPython device.
+
+Usage:
+1. Connect to your MicroPython board's REPL
+2. Run this example
+3. Connect the device to a host computer via USB
+4. The device should appear as an MTP device (like a camera or media player)
+5. Files can be accessed through the host's file browser
+"""
+
+import os
+import time
+import usb.device
+from usb.device.mtp import MTPInterface
+
+def main():
+    """Main function to run the MTP example."""
+    # Print startup message
+    print("MicroPython USB MTP Example")
+    print("===========================")
+    
+    # Create MTP interface to expose the filesystem
+    # The root_dir parameter sets which directory to expose via MTP
+    # Here we use '/' to expose the entire filesystem
+    mtp = MTPInterface(root_dir="/")
+    
+    # Initialize the MTP interface
+    mtp.init()
+    
+    # Initialize the USB device with the MTP interface
+    # This registers the device with USB and starts accepting connections
+    usb.device.get().init(mtp, builtin_driver=True)
+    
+    # Wait for USB to be configured
+    print("Waiting for USB connection...")
+    while not mtp.is_open():
+        time.sleep(0.1)
+    
+    print("USB MTP device connected!")
+    print("You can now access files via the host computer")
+    print("Press Ctrl+C to exit")
+    
+    try:
+        # Keep the program running to maintain the USB connection
+        while True:
+            time.sleep(1)
+    except KeyboardInterrupt:
+        # Clean up on exit
+        print("Exiting MTP example")
+
+if __name__ == "__main__":
+    main()

micropython/usb/usb-device-mtp/manifest.py

@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: MIT
+# Copyright (c) 2023 MicroPython Team
+
+# This file is part of the MicroPython project, https://micropython.org/
+# The MIT License (MIT)
+# Note: this file is used by the MicroPython build system to determine module dependencies
+#
+requires = ["usb-device"]
+version = "0.1.0"