The tinySA ULTRA now enumerates as a composite device: the CDC serial
port plus a mass storage interface (Bulk-Only Transport, SCSI). The SD
card is only presented to the PC in USB DISK mode (STORAGE menu or shell
command 'usbdisk on|off'), which stops sweeping and screen updates so the
mass storage thread owns SPI1 and spi_buffer. Outside the mode the PC
sees an empty card reader, so the serial port never re-enumerates. The
mode ends on touch, jog button, eject from the PC, card removal or
'usbdisk off'.
- usb_msc.c/h: mass storage thread, BOT state machine, SCSI commands
- usbcfg.c: composite descriptors (IAD, bcdDevice 0x0201), bulk EP3,
requests hook, packet memory reuse on a repeated SET_CONFIGURATION and
data toggle reset on CLEAR_FEATURE (both specific to this ChibiOS fork)
- ui.c: USB DISK menu item and mode screen
- main.c: 'usbdisk' command; shell commands that could use SPI1 are
refused while the mode is active
F072 builds are unchanged. Tested on HW V0.5.4 with Windows 11: about
620 KB/s read and 370 KB/s write, data verified against FatFs reads.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
erikkaashoek