boot.py

import usb_hid

# This is only one example of a gamepad descriptor, and may not suit your needs.
GAMEPAD_REPORT_DESCRIPTOR = bytes((
    0x05, 0x01,  # Usage Page (Generic Desktop Ctrls)
    0x09, 0x05,  # Usage (Game Pad)
    0xA1, 0x01,  # Collection (Application)
    0x85, 0x01,  # Report ID (will be replaced at runtime)
    0x05, 0x09,  # Usage Page (Button)
    0x19, 0x01,  # Usage Minimum (Button 1)
    0x29, 0x10,  # Usage Maximum (Button 16)
    0x15, 0x00,  # Logical Minimum (0)
    0x25, 0x01,  # Logical Maximum (1)
    0x75, 0x01,  # Report Size (1)
    0x95, 0x10,  # Report Count (16)
    # Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
    0x81, 0x02,
    0x05, 0x01,  # Usage Page (Generic Desktop Ctrls)
    0x15, 0x81,  # Logical Minimum (-127)
    0x25, 0x7F,  # Logical Maximum (127)
    0x09, 0x30,  # Usage (X)
    0x09, 0x31,  # Usage (Y)
    0x09, 0x32,  # Usage (Z)
    0x09, 0x35,  # Usage (Rz)
    0x75, 0x08,  # Report Size (8)
    0x95, 0x04,  # Report Count (4)
    # Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
    0x81, 0x02,
    0xC0,        # End Collection
))

gamepad = usb_hid.Device(
    report_descriptor=GAMEPAD_REPORT_DESCRIPTOR,
    usage_page=0x01,           # Generic Desktop Control
    usage=0x05,                # Gamepad
    in_report_length=6,        # This gamepad sends 6 bytes in its report.
    out_report_length=0,       # It does not receive any reports.
    report_id_index=7,         # The report id is at byte 7 (counting from 0)
                               # in the report descriptor.
)

usb_hid.enable((gamepad,))
print("enabled HID with custom gamepad device")