usb_selftest_wlun Directory Reference

Directory dependency graph for usb_selftest_wlun:

Directories
	inc
	src

Detailed Description

The write-path counterpart to the read-only MSC self-loops: it exercises the host-to-device bulk-OUT data phase (SCSI WRITE(10)). The two USB ports are cabled to each other and one firmware image runs both stacks.

USBFS on J11 is the device: a ThreadX + USBX Mass-Storage class exposing a single writable logical unit backed by a small RAM disk, whose media_write copies host data in and whose media_read serves it back. USBHS on J7 is the polled first-party host: it enumerates the device, WRITE(10)s a deterministic per-LBA pattern across the whole disk in bursts, then READ(10)s it back and byte-checks every sector against the same pattern.

Because the host writes the data and reads it back, the loop proves the device bulk-OUT WRITE data phase round-trips intact over USB on chip – the capability that gates writable OSPI, CDC and HID. s_dbg_mismatch holds the first differing sector, or an all-ones sentinel when every sector matched.

The four things a bulk-OUT data phase needs

All four have to be right together; any one missing stalls or corrupts the transfer, and this app is what proves them on hardware.

1. Host MPS. Chunk the data-out at the device's enumerated endpoint wMaxPacketSize (64 at full speed), not at the host controller's speed ceiling (512 at high speed). ra8_usb_host_bulk_out ships one packet per call.
2. Device DBLB. Double-buffer the device bulk-OUT pipe so the host's next packet lands in bank B while the ISR drains bank A.
3. Loop-drain. The DCD drains every ready OUT bank per interrupt, not just one.
4. Single-chunk buffer. UX_SLAVE_REQUEST_DATA_MAX_LENGTH = 4096 keeps a typical WRITE inside one device transfer, avoiding an inter-chunk gap.

Pinout

FS device: P4_07 VBUS sense, P5_00 VBUSEN GPIO low, P8_14/P8_15 data (PSEL usb_fs). HS host: SW4-8 to Host via the U15 expander, PD07 high so U18 powers J7, P4_08 VBUS sense (PSEL usb_hs). Console on PD_02/PD_03, SCI8.

The device side advertises VID 0x1209, PID 0x0014. Bench use only.