MSC Dual LUN

A USB Mass Storage device that presents two logical units (LUNs), each a small in-RAM FAT12 disk.

What it does

Exposes two LUNs, each a 8 KB FAT12 RAM disk containing a README.TXT file (TinyUSB 0 and TinyUSB 1 volumes).
Both disks are read/write by default, so host changes are written back to RAM (unless built read-only).
Pressing the board button marks LUN1 as "not ready" to simulate removable media being absent (e.g. SD card removed).
Reports a custom SCSI inquiry: vendor TinyUSB, product Mass Storage, revision 1.0.
Runs under no-OS, FreeRTOS or ThreadX (USB device and LED blink as separate tasks under an RTOS).
LED blink rate indicates bus state (not mounted / mounted / suspended).

USB Descriptors

Interface	Class driver
0	MSC (mass storage)

Configuration

Notable tusb_config.h settings:

#define CFG_TUD_MSC               1
#define CFG_TUD_MSC_EP_BUFSIZE    512

Building

CMake:

mkdir build && cd build
cmake -DBOARD=raspberry_pi_pico ..
cmake --build .

Make:

make BOARD=raspberry_pi_pico all

Try it

After plugging in, two removable drives appear on the host, each containing a README.TXT. Open or modify the files to exercise reads and writes. Press the board button to make the second drive report "not ready" (medium not present).