dualbank – Dualbank Module

The dualbank module adds ability to update and switch between the two identical app partitions, which can contain different firmware versions.

Having two partitions enables rollback functionality.

The two partitions are defined as the boot partition and the next-update partition. Calling dualbank.flash() writes the next-update partition.

After the next-update partition is written a validation check is performed and on a successful validation this partition is set as the boot partition. On next reset, firmware will be loaded from this partition.

Use cases:

  • Can be used for OTA Over-The-Air updates.

  • Can be used for dual-boot of different firmware versions or platforms.

Note

Boards with flash =2MB:

This module is unavailable as the flash is only large enough for one app partition.

Boards with flash >2MB:

This module is enabled/disabled at runtime based on whether the CIRCUITPY drive is extended or not. See storage.erase_filesystem() for more information.

import dualbank

dualbank.flash(buffer, offset)
dualbank.switch()
dualbank.flash(buffer: circuitpython_typing.ReadableBuffer, offset: int = 0) → None

Writes one of the two app partitions at the given offset.

This can be called multiple times when flashing the firmware in smaller chunks.

Parameters:

  • buffer (ReadableBuffer) – The entire firmware or a partial chunk.

  • offset (int) – Start writing at this offset in the app partition.

dualbank.switch() → None

Switches to the next-update partition.

On next reset, firmware will be loaded from the partition just switched over to.