class Flash – access to built-in flash storage¶

The Flash class allows direct access to the primary flash device on the STM32-based OpenMV Cams.

In most cases, to store persistent data on the device, you’ll want to use a higher-level abstraction, for example the filesystem via Python’s standard file API, but this interface is useful to customise the filesystem configuration or implement a low-level storage system for your application.

Note

The OpenMV Cam H7 Plus, Pure Thermal and N6 use an external SPI/QSPI/XSPI flash chip for primary storage; the other STM32-based OpenMV Cams use the internal flash inside the MCU. The Python interface is identical in both cases.

Constructors¶

class pyb.Flash¶

class pyb.Flash(*, start: int = -1, len: int = -1)

Construct a vfs.AbstractBlockDev-compatible block device for the on-board flash. Two forms exist:

Flash() (no arguments): returns the legacy singleton object that exposes the whole flash with a virtual partition table prepended. The actual flash data starts at block 0x100. This form is deprecated and will be removed in a future MicroPython release.
Flash(start=..., len=...): returns a fresh block device that accesses the flash starting at byte offset start (default 0) for len bytes (default: the remainder of the device). Both values must be a multiple of the underlying block size (typically 512 bytes for internal flash; the external SPI/QSPI/XSPI parts use a larger erase-sector size).

Methods¶

readblocks(block_num: int, buf: bytearray) → None¶

readblocks(block_num: int, buf: bytearray, offset: int) → None

Read bytes from the flash into buf. Two overloads expose the simple and extended interfaces:

Simple form (readblocks(block_num, buf)): reads whole blocks starting at block index block_num. len(buf) must be a multiple of the flash block size.

Extended form (readblocks(block_num, buf, offset)): reads len(buf) bytes – not necessarily a whole number of blocks – starting at byte offset within block block_num. len(buf) has no alignment constraint. Only supported on objects created with explicit start / len arguments, not on the deprecated singleton.

writeblocks(block_num: int, buf: bytes | bytearray) → None¶

writeblocks(block_num: int, buf: bytes | bytearray, offset: int) → None

Write bytes from buf to the flash. Two overloads expose the simple and extended interfaces:

Simple form (writeblocks(block_num, buf)): writes whole blocks starting at block index block_num. len(buf) must be a multiple of the flash block size. Each affected block is erased automatically before being written.

Extended form (writeblocks(block_num, buf, offset)): writes len(buf) bytes – not necessarily a whole number of blocks – starting at byte offset within block block_num. len(buf) has no alignment constraint, and no implicit erase is performed – the caller must ensure the affected blocks have been erased via a prior ioctl(6, block_num) call. Only supported on objects created with explicit start / len arguments.

ioctl(cmd: int, arg: int) → int | None¶: Standard vfs.AbstractBlockDev ioctl entry point. See vfs.AbstractBlockDev.ioctl() for the full list of cmd values. cmd=5 returns the flash block size in bytes; cmd=6 erases the block with index arg.