usb_msc_mram_steps.h File Reference

Shared geometry constants + FAT16 sector-synthesis prototype. More...

#include <stdint.h>
#include "ux_api.h"

Include dependency graph for usb_msc_mram_steps.h:

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Enumerations
enum	demo_config_t : uint32_t {   k_demo_thread_stack = 4096U ,   k_demo_usbx_pool_bytes = 32768U ,   k_demo_block_size = 512U ,   k_demo_idle_ticks = 50U }
	Compile-time settings for the worker thread + USBX pool + RAM-disk geometry. More...
enum	demo_mram_t : uint32_t {   k_mram_base_addr = 0x02000000U ,   k_mram_bytes = 0x00100000U }
	The MRAM window this volume exposes (RA8D2 HUM memory map). More...
enum	demo_fat_geom_t : uint32_t {   k_fat_reserved_sectors = 1U ,   k_fat_num_fats = 1U ,   k_fat_fat_sectors = 17U ,   k_fat_root_entries = 512U ,   k_fat_root_sectors = 32U ,   k_fat_data_sectors = 4096U ,   k_fat_fat_lba = 1U ,   k_fat_root_lba = 18U ,   k_fat_data_lba = 50U ,   k_fat_total_sectors = 4146U ,   k_fat_first_cluster = 2U ,   k_fat_mram_clusters = 2048U ,   k_fat_last_mram_clus = 2049U ,   k_fat_entries_per_sec = 256U ,   k_fat_eoc = 0xFFFFU ,   k_fat_entry0 = 0xFFF8U }
	Synthesized FAT16 volume geometry (MS FAT spec 1.03). More...
enum	demo_fat_boot_t : uint32_t {   k_boot_jmp0 = 0xEBU ,   k_boot_jmp1 = 0x3CU ,   k_boot_jmp2 = 0x90U ,   k_boot_media = 0xF8U ,   k_boot_sec_per_trk = 32U ,   k_boot_num_heads = 16U ,   k_boot_drive_num = 0x80U ,   k_boot_ext_sig = 0x29U ,   k_boot_volume_id = 0x52A8D200U ,   k_boot_sig_lo = 0x55U ,   k_boot_sig_hi = 0xAAU ,   k_boot_sig_lo_off = 510U ,   k_boot_sig_hi_off = 511U }
	Boot-sector field values (MS FAT spec 1.03 sec 3.1). More...
enum	demo_fat_off_t : uint8_t {   k_bpb_off_jmp = 0U ,   k_bpb_off_oem = 3U ,   k_bpb_off_bps = 11U ,   k_bpb_off_spc = 13U ,   k_bpb_off_rsvd = 14U ,   k_bpb_off_nfats = 16U ,   k_bpb_off_rootent = 17U ,   k_bpb_off_totsec16 = 19U ,   k_bpb_off_media = 21U ,   k_bpb_off_fatsz16 = 22U ,   k_bpb_off_spt = 24U ,   k_bpb_off_heads = 26U ,   k_bpb_off_drvnum = 36U ,   k_bpb_off_bootsig = 38U ,   k_bpb_off_volid = 39U ,   k_bpb_off_label = 43U ,   k_bpb_off_fstype = 54U ,   k_dir_entry_bytes = 32U ,   k_dir_off_attr = 11U ,   k_dir_off_cluster_lo = 26U ,   k_dir_off_size = 28U ,   k_dir_attr_volume = 0x08U ,   k_dir_attr_read_only = 0x01U ,   k_dir_name_bytes = 11U ,   k_byte_shift = 8U ,   k_byte_mask = 0xFFU }
	Byte offsets inside the boot sector and directory entries. More...
enum	demo_word_pack_t : uint32_t {   k_word_shift = 16U ,   k_word_mask = 0xFFFFU }
	32-bit little-endian split constants. More...

Functions
void	demo_fat_fill_sector (uint32_t lba, UCHAR *out)
	Synthesize one 512-byte sector of the read-only volume.

Detailed Description

Shared geometry constants + FAT16 sector-synthesis prototype.

Tag

[Ring 6 / APP] {World: S}

Declares the compile-time FAT16 volume-geometry / boot-sector / offset enums plus the read-only sector-synthesizer that main.c and usb_msc_mram_steps.c share. The enums live here so the on-the-fly volume image stays a single source of truth: the worker thread in main.c reads geometry constants such as k_fat_total_sectors and k_demo_block_size to size the LUN, while the synthesis helpers in usb_msc_mram_steps.c consume the same byte-offset and field-value constants to build each 512-byte sector.

Author

Brighton Sikarskie

Date

2026-05-02

Copyright

Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since

0.1.0

Definition in file usb_msc_mram_steps.h.

Enumeration Type Documentation

demo_config_t

enum demo_config_t : uint32_t

Compile-time settings for the worker thread + USBX pool + RAM-disk geometry.

Enumerator
k_demo_thread_stack	Worker thread stack (bytes).
k_demo_usbx_pool_bytes	USBX memory pool (bytes).
k_demo_block_size	SCSI logical block size (bytes).
k_demo_idle_ticks	Heartbeat back-off (ThreadX ticks).

Definition at line 34 of file usb_msc_mram_steps.h.

demo_fat_boot_t

enum demo_fat_boot_t : uint32_t

Boot-sector field values (MS FAT spec 1.03 sec 3.1).

Enumerator
k_boot_jmp0	Short JMP opcode.
k_boot_jmp1	JMP displacement.
k_boot_jmp2	NOP.
k_boot_media	Fixed-disk media byte.
k_boot_sec_per_trk	Geometry filler.
k_boot_num_heads	Geometry filler.
k_boot_drive_num	BIOS drive number.
k_boot_ext_sig	Extended boot signature.
k_boot_volume_id	Arbitrary volume serial.
k_boot_sig_lo	Boot signature low byte.
k_boot_sig_hi	Boot signature high byte.
k_boot_sig_lo_off	Signature low-byte offset.
k_boot_sig_hi_off	Signature high-byte offset.

Definition at line 84 of file usb_msc_mram_steps.h.

demo_fat_geom_t

enum demo_fat_geom_t : uint32_t

Synthesized FAT16 volume geometry (MS FAT spec 1.03).

One 512-byte sector per cluster. The data region is padded to 4096 clusters so the cluster count crosses the 4085 FAT16 threshold; only the first 2048 clusters (1 MiB) are backed by MRAM, and nothing references the rest. FAT16 needs 2 bytes per entry for 4098 entries = 8196 bytes = 17 sectors. The root directory holds 512 entries = 32 sectors.

Enumerator
k_fat_reserved_sectors	Boot sector only.
k_fat_num_fats	Single FAT copy.
k_fat_fat_sectors	FAT16 size for 4098 entries.
k_fat_root_entries	Root directory entries.
k_fat_root_sectors	512 entries x 32 B / 512 B.
k_fat_data_sectors	Padded data region (>= 4085).
k_fat_fat_lba	First FAT sector.
k_fat_root_lba	First root-directory sector.
k_fat_data_lba	First data sector (cluster 2).
k_fat_total_sectors	1 + 17 + 32 + 4096.
k_fat_first_cluster	FAT data area starts at cluster 2.
k_fat_mram_clusters	Clusters backed by MRAM (1 MiB).
k_fat_last_mram_clus	Last cluster of MRAM.BIN.
k_fat_entries_per_sec	FAT16 entries per 512-byte sector.
k_fat_eoc	End-of-chain marker.
k_fat_entry0	FAT[0]: media F8 + filler.

Definition at line 61 of file usb_msc_mram_steps.h.

demo_fat_off_t

enum demo_fat_off_t : uint8_t

Byte offsets inside the boot sector and directory entries.

Enumerator
k_bpb_off_jmp	Jump instruction.
k_bpb_off_oem	OEM name (8 bytes).
k_bpb_off_bps	Bytes per sector.
k_bpb_off_spc	Sectors per cluster.
k_bpb_off_rsvd	Reserved sector count.
k_bpb_off_nfats	Number of FATs.
k_bpb_off_rootent	Root entry count.
k_bpb_off_totsec16	Total sectors (16-bit).
k_bpb_off_media	Media descriptor.
k_bpb_off_fatsz16	Sectors per FAT.
k_bpb_off_spt	Sectors per track.
k_bpb_off_heads	Head count.
k_bpb_off_drvnum	Drive number.
k_bpb_off_bootsig	Extended boot signature.
k_bpb_off_volid	Volume serial (4 bytes).
k_bpb_off_label	Volume label (11 bytes).
k_bpb_off_fstype	Filesystem type (8 bytes).
k_dir_entry_bytes	Directory entry size.
k_dir_off_attr	Attribute byte.
k_dir_off_cluster_lo	First cluster (low word).
k_dir_off_size	File size (32-bit LE).
k_dir_attr_volume	Volume-label attribute.
k_dir_attr_read_only	Read-only attribute.
k_dir_name_bytes	8.3 name field length.
k_byte_shift	Bits per byte for LE packing.
k_byte_mask	Low-byte mask.

Definition at line 104 of file usb_msc_mram_steps.h.

demo_mram_t

enum demo_mram_t : uint32_t

The MRAM window this volume exposes (RA8D2 HUM memory map).

Enumerator
k_mram_base_addr	MRAM code window base address.
k_mram_bytes	1 MiB window size.

Definition at line 45 of file usb_msc_mram_steps.h.

demo_word_pack_t

enum demo_word_pack_t : uint32_t

32-bit little-endian split constants.

Enumerator
k_word_shift	Bits per half-word.
k_word_mask	Low half-word mask.

Definition at line 137 of file usb_msc_mram_steps.h.

Function Documentation

demo_fat_fill_sector()

void demo_fat_fill_sector	(	uint32_t	lba,
		UCHAR *	out )

Synthesize one 512-byte sector of the read-only volume.

Dispatches on the LBA: boot sector, FAT, root directory, or data region. Data sectors inside the MRAM.BIN chain are copied straight out of the 1 MiB MRAM window; padding clusters past the chain read as zeros.

Parameters

[in]	lba	Logical block address inside the volume.
[out]	out	512-byte destination buffer.

Precondition

lba is below k_fat_total_sectors (caller-checked).

out has 512 writable bytes.

Postcondition

out holds the synthesized sector content.

No other state changes.

Note

Reads chip MRAM directly; no caching.

Since

0.1.0

Definition at line 199 of file usb_msc_mram_steps.c.

References demo_fat_fill_boot(), demo_fat_fill_fat(), demo_fat_fill_root(), k_demo_block_size, k_fat_data_lba, k_fat_fat_lba, k_fat_first_cluster, k_fat_last_mram_clus, k_fat_root_lba, k_mram_base_addr, memcpy(), and memset().

Referenced by demo_msc_read().