ra8_io_xspi_demo Directory Reference

Directory dependency graph for ra8_io_xspi_demo:

Directories
	inc
	src

Detailed Description

The ra8_io fabric (#155, #156) over the on-board Octo-SPI NOR flash – a third storage tier alongside the RAM (ra8_io_demo) and SD (ra8_io_sd_demo) cases.

NOR is what makes this one different. It is an erase-before-write medium: a program operation can only clear bits, so a 4 KiB sector has to be erased back to all-ones before any byte in it is rewritten. Every 512-byte block write therefore drives a whole-sector erase-and-reprogram read-modify-write inside the backend. That exercises the block-device capability flags (must_erase_before_write, whole-sector RMW) that the RAM and SD backends never trigger, which is the reason this app exists.

Above the block device everything is the fabric as usual: bridge to ra8_fs, format and mount FAT12, register in the VFS, mkdir, write a payload, read it back through the VFS path and byte-compare. The controller comes up in 1S-1S-1S link mode via ra8_xspi_init. The window and payload are kept deliberately small because each write costs a full sector RMW.

The real part is an IS25LX512M. Its bus is the constraint to watch on this bench: the Octo-SPI pins are the PMOD1 pins, so anything else wired onto PMOD1 takes the flash away from this app and it cannot reach its storage. The carrier PCB (#318) is the way out.