RE: Bootloader and SoftDevice compatibility

Michael — Wed, 10 Apr 2019 16:13:56 GMT

All right, that's what we needed to know. Thanks!

RE: Bootloader and SoftDevice compatibility

Einar Thorsrud — Wed, 10 Apr 2019 06:45:30 GMT

Hi,

The BLE bootloader depends on the SoftDevice, and there is typically always API changes with new version numbers of the SoftDevice. Therefore, upgrading the SoftDevice without upgrading the bootloader will typically cause the bootloader to fail, effectively bricking the device. For that reason, the bootloader enforces that the bootloader itself must be upgraded simultaneously with a SoftDevice with different major version. A simultaneous upgrade of SD+BL is not enforced when only the minor version of the SoftDevice is upgraded, but you should make sure to test properly in this case as well, so that you are confident that there will be no problems, before shipping the DFU upgrade package to customers.

The SoftDevice independence is the same for the app and the bootloader. What this means is that they are not linked together, but instead the API is based on supervisor calls (SVC). However, the mapping between SVC numbers and parameters etc. must be up do date, as this typically changes between SoftDevice versions. This is what constitutes the SoftDevice API. See Application programming interface in the SoftDevice specification for details.