SPI Block Device Driver.

This is a combination of a raw SPI flash driver and a minimal block device driver to use a SPI connected flash device for a MicroPython file system. The focus of that driver is small size and simplicity, not speed. Nevertheless, it works reasonably fast. It shall be used with a VFS file system, which takes care of only writing to erased areas. A more generic NV memory driver can be found at https://github.com/peterhinch/micropython_eeprom, which supports different types of memory, any write sizes and spanning the memory space over multiple chips.

Constructors:

flash = SPIflash(spi, cs, *, addr4b=False, size=None, pagesize=256, sectorsize=4096)

spi has to b a SPI object, cs must be a Pin object of the cs pin. If addr4b is True, a 4 byte addressing mode is used for the flash, otherwise 3 byte addresses are used, which are sufficient up to a flash size of 16 MByte.

The optional parameters size, pagesize and sectorsize allow using devices with non-standard or non-detectable values for these properties.

bdev = FlashBdev(flash )

flash is a SPIflash object created e.g. from spiflash.py.

The drivers were tested with LittleFS Version 1 and 2, and also with a FAT file system. The latter is NOT recommended. When using the driver with SoftSPI, select LFS1 as file system. That is less space efficient, but faster. The Lfs progsize parameter must not be less than 128.

SPIflash Methods:

flash.flash_read(addr, buffer)

Read data from addres into the buffer. The amount of data is defined by the buffer size.

flash.flash_write(addr, buffer)

Write data from the buffer at the address. The amount of data is defined by the buffer size. The data is written in multiples of up to a page size, such that a single write does not cross a page boundary.

flash.flash_erase(addr)

Erase the sector at addr.

flash.flash_size()

Return the total size of the flash as bytes. . This information is required by a file system block device driver.

flash.flash_sectorsize()

Return the size of a sector. This information is required by a file system block device driver.

Examples:

# Using HARD spi
import os
from flashbdev import FlashBdev
from spiflash import SPIflash
from machine import SPI, Pin

spi=SPI(0, sck=Pin("FLASH_SCK"), mosi=Pin("FLASH_MOSI"), miso=Pin("FLASH_MISO"), baudrate=12_000_000)
cs = Pin("FLASH_CS", Pin.OUT, value=1)

flash=FlashBdev(SPIflash(spi, cs))
try:
    vfs = os.VfsLfs1(flash, progsize=256)
except OSError as e:
    print("Mount failed with error", e)
    print("Recreate the file system")  # Previous content is lost!
    os.VfsLfs1.mkfs(flash, progsize=256)
    vfs = os.VfsLfs1(flash, progsize=256)

os.mount(vfs, "/flash")

# Example using SoftSPI with a QSPI device.
import os
from flashbdev import FlashBdev
from spiflash import SPIflash
from machine import SPI, Pin

wp = Pin("PA10", Pin.OUT, value=1)
hold = Pin("PA11", Pin.OUT, value=1)
cs = Pin("PB11", Pin.OUT, value=1)
spi = SoftSPI(sck="PB10", mosi="PA08", miso="PA09", baudrate=2_000_000)

flash=FlashBdev(SPIflash(spi, cs))
try:
    vfs = os.VfsLfs1(flash, progsize=256)
except OSError as e:
    print("Mount failed with error", e)
    print("Recreate the file system")  # Previous content is lost!
    os.VfsLfs1.mkfs(flash, progsize=256)
    vfs = os.VfsLfs1(flash, progsize=256)

os.mount(vfs, "/flash")

robert-hh / SPI_Flash