10.2.1: Extra but unusable disk drive with QT Py ESP32-S3

[wireddown]

CircuitPython version and board name

Adafruit CircuitPython 10.2.1 on 2026-05-13; Adafruit QT Py ESP32-S3 4MB Flash 2MB PSRAM with ESP32S3
Board ID:adafruit_qtpy_esp32s3_4mbflash_2mbpsram
UID:4F21AFA56341
MAC:54:64:CB:3F:40:4F

Code/REPL

"""Windows demo

pip install pyserial wmi
"""

from pprint import pprint

from serial.tools.list_ports_windows import comports

discovered_comports = {
    comport.device: {
        "com_port": comport.device,
        "com_id": comport.hwid,
        "serial_number": comport.serial_number,
    }
    for comport in sorted(comports()) if comport.device != "COM1"
}
pprint(discovered_comports)
print()

from wmi import WMI

disks_and_serial_numbers = {}
host_pc = WMI()
for disk in list(host_pc.Win32_PhysicalMedia()):
    # Full value has format '\\\\.\\PHYSICALDRIVE0'
    disk_id = disk.wmi_property("Tag").value.split("\\")[-1]
    serial_number = disk.wmi_property("SerialNumber").value
    disks_and_serial_numbers.update(
        {
            disk_id: {
                "serial_number": serial_number,
            }
        }
    )
pprint(disks_and_serial_numbers)
print()

partitions_and_disks = {}
for entry in list(host_pc.Win32_DiskDriveToDiskPartition()):
    # Full value has format '\\\\HOSTNAME\\root\\cimv2:Win32_DiskPartition.DeviceID="Disk #0, Partition #0"'
    partition = entry.wmi_property("Dependent").value.split("=")[-1].replace('"', "")
    # Full value has format '\\\\HOSTNAME\\root\\cimv2:Win32_DiskDrive.DeviceID="\\\\\\\\.\\\\PHYSICALDRIVE0"'
    disk_id = entry.wmi_property("Antecedent").value.split("=")[-1].replace('"', "").split("\\")[-1]
    partitions_and_disks.update(
        {
            disk_id: {
                "drive_partition": partition,
            }
        }
    )
pprint(partitions_and_disks)
print()

drive_letters_and_partitions = {}
for entry in list(host_pc.Win32_LogicalDiskToPartition()):
    # Full value has format '\\\\HOSTNAME\\root\\cimv2:Win32_LogicalDisk.DeviceID="C:"'
    drive_letter = entry.wmi_property("Dependent").value.split("=")[-1].replace('"', "")
    # Full value has format '\\\\HOSTNAME\\root\\cimv2:Win32_DiskPartition.DeviceID="Disk #0, Partition #2"'
    drive_partition = entry.wmi_property("Antecedent").value.split("=")[-1].replace('"', "")
    drive_letters_and_partitions.update(
        {
            drive_partition: {
                "drive_root": drive_letter,
            }
        }
    )
pprint(drive_letters_and_partitions)
print()

drive_letters_and_labels = {}
for volume in list(host_pc.Win32_Volume()):
    drive_letter = volume.wmi_property("DriveLetter").value
    if drive_letter:
        drive_label = volume.wmi_property("Label").value
        drive_letters_and_labels.update(
            {
                drive_letter: {
                    "drive_label": drive_label,
                }
            }
        )
pprint(drive_letters_and_labels)

Behavior

Running the Python code above on my Windows PC results in this output.

The code searches for serial ports and collects storage information from WMI.

Note that I used diff syntax so that I can highlight specific lines.

python demo.py

  {'COM4': {'com_id': 'USB VID:PID=239A:8144 SER=4F21AFA56341 LOCATION=1-7:x.0',
            'com_port': 'COM4',
+           'serial_number': '4F21AFA56341'}}

  {'PHYSICALDRIVE0': {'serial_number': '6479_A750_C0D0_13BD.'},
   'PHYSICALDRIVE1': {'serial_number': 'E823_8FA6_BF53_0001_001B_448B_47AF_9EF8.'},
+  'PHYSICALDRIVE2': {'serial_number': '4F21AFA56340'},
+  'PHYSICALDRIVE3': {'serial_number': '4F21AFA56341'}}

  {'PHYSICALDRIVE0': {'drive_partition': 'Disk #0, Partition #2'},
   'PHYSICALDRIVE1': {'drive_partition': 'Disk #1, Partition #0'},
   'PHYSICALDRIVE2': {'drive_partition': 'Disk #2, Partition #0'}}

  {'Disk #0, Partition #1': {'drive_root': 'C:'},
   'Disk #1, Partition #0': {'drive_root': 'X:'},
   'Disk #2, Partition #0': {'drive_root': 'E:'}}

  {'C:': {'drive_label': 'Windows'},
-  'D:': {'drive_label': None},
+  'E:': {'drive_label': 'CIRCUITPY'},
   'X:': {'drive_label': 'xtra'}}

Observations

• The serial number for the QT Py's serial port matches the serial number for PHYSICALDRIVE3
• PHYSICALDRIVE3 has no partitions and it presents as D:
• Instead, the QT Py's disk drive is E: and belongs to PHYSICALDRIVE2
• The serial number for the QT Py's drive is off-by-one from its serial port

The extra disk drive also presents in Explorer.

Description

This behavior seems similar to this report for CircuitPython 10.0.0-alpha.2 on Raspberry Pi Pico W with rp2040

https://forums.adafruit.com/viewtopic.php?p=1052262

but instead the device is Adafruit QT Py ESP32-S3 4MB Flash.

For Adafruit QT Py ESP32-S3 devices, is this a bug or expected behavior?

If this is expected for CircuitPython 10, would it be possible to declare the same serial number for the UART and disk drive, and use the off-by-one serial number for the extra drive?

Additional information

In my projects, I use a matching serial number between COM ports and physical drives to detect CircuitPython devices and separate them from other COM ports and disk drives.

When I upgraded one of my QT Py devices from CircuitPython 9 to CircuitPython 10, I noticed this new disk drive and off-by-one serial number because my CircuitPython detection code started returning empty results.

[dhalbert]

The MSC device has two LUN's, because one is optionally for presenting an SD card when it is mounted. The other is regular CIRCUITPY. See https://docs.circuitpython.org/en/latest/docs/workflows.html#sd-card-drive.

[wireddown]

Thank you!~

So it sounds like even though there isn't an SD card slot on the module itself -- Adafruit QT Py S3 -- because it does have the bus capability to interface with an SD reader, then the CircuitPython image for it has this compiled in.

If so, then I would like to ask:

Would it be possible to swap serial numbers on the LUNs so that the serial number for CIRCUITPY drive matches the serial number for the UART?

[dhalbert]

I think Windows is assigning those serial numbers, not us, and is making them distinguishable by incrementing the base serial number. On Linux, if I do

ls -al /dev/disk/by-id

then I get this kind of result for a CircuitPython board. On Linux, the partitions are disambiguated by adding a suffix, not by incrementing the serial number. sda and sdb are the two LUNs, and sda1 is the actual CIRCUITPY partition

rwxrwxrwx  1 root root   9 Jun 27 08:18 usb-Adafruit_Metro_ESP32-S3_435881D847CC-0:0 -> ../../sda
lrwxrwxrwx  1 root root  10 Jun 27 08:18 usb-Adafruit_Metro_ESP32-S3_435881D847CC-0:0-part1 -> ../../sda1
lrwxrwxrwx  1 root root   9 Jun 27 08:17 usb-Adafruit_Metro_ESP32-S3_435881D847CC-0:1 -> ../../sdb

The 435881D847CC is the unique serial for the whole device. From boot_out.txt:

Adafruit CircuitPython 10.3.0-alpha.3-4-g17196f7eed-dirty on 2026-06-26; Adafruit Metro ESP32S3 with ESP32S3
Board ID:adafruit_metro_esp32s3
UID:435881D847CC
MAC:34:85:18:8D:74:CC

So if you're trying to match the numbers, you could try nearby numbers.