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sdfile.md

File metadata and controls

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SDFILE / SYDFS

This is a simple "filesystem" that can contain a number of named files, in a flat structure.

Format

Flash header

struct sydfs_hdr {
  uint16_t  hdr_crc;    /* Header CRC */
  uint16_t  list_crc;   /* File list CRC */
  uint32_t  info1;
  uint32_t  info2;
  uint32_t  count;      /* File count */
  uint32_t  version1;
  uint32_t  version2;
  uint8_t   chiptype[8];
};
  • u16: CRC16 of the header
    • Excluding this field
  • u16: CRC16 of the file list
    • If the file entries are encrypted, then this means the CRC16 of them encrypted, i.e. as they're stored in flash.
  • u32: Info 1
    • Usually this is set to the filesystem size
  • u32: Info 2
    • 0xFFFFFFFD
  • u32: File count
  • u32: Version 1
  • u32: Version 2
  • u8[8]: Chip type

File header

struct sydfs_ent {
  uint8_t   type;       /* File type */
  uint8_t   resvd;      /* (reserved) */
  uint16_t  data_crc;   /* Data CRC */
  uint32_t  offset;     /* Data offset */
  uint32_t  size;       /* File size */
  uint32_t  index;      /* Index */
  char      name[16];   /* File name */
};
  • u8: File type
    • (as per AC69xx or AC5xxx:)
    • 0 = Undefined
    • 1 = uboot.boot ~ Bootloader
    • 2 = user.app ~ Application
    • 3 = cmd_zone, __zone2.zon, _____.____2 ~ Zones
    • 4 = sdram.apu ~ Compressed app
    • 5 = ver.bin ~ Version file
    • 6 = sys.cfg ~ System config
    • 7 = spc.aer ~ Special area
    • 8 = chip_key.bin ~ Chip key
  • u8: (reserved)
  • u16: CRC16 of data
    • Sometimes this is not just the raw CRC16 (e.g. for encrypted firmware regions)
  • u32: Data offset
  • u32: Data length
  • u32: Index
  • u8[16]: File name
    • Null-terminated, unless the name is exactly 16 bytes long.