Unused space at the end of the SoftDevice region?

[Jeff Wiencrot]

Hello!  The S140 7.3.0 SoftDevice docs say it requires 0x27000 of flash, but the SoftDevice hex only occupies 0x26634 bytes.  This leaves 2508 bytes of hopefully unused flash.

Can I use some of that remaining space to store some permanent metadata I need in my image?  This would be data programmed into the device with the SoftDevice and not modified by the firmware at any point.  I have ~256-512 bytes of data and I'm hoping to stick it in this space.

Thanks!

[Einar Thorsrud]

Hi,

Due to the nature of flash. memory, we always specify full number of flash pages as the SoftDevice size. Any free space betwen the end of the data and the end of the page would be erased during a SoftDevice DFU update ofr instance (as the flash pages are erased), so it is not recomended to re-use that space. It may be possible though if you do not do DFU and are aware of the limitations and that it is not supported, but I would try to avoid it. Could another posibility be to store additional data in the UICR? Have quite a few registers there, and except for those that are reserved, you can use them for enything persistent data.

[Jeff Wiencrot]

Einar Thorsrud thank you for the quick answer!  I kind of figured this was just about page alignment due to flash erase sizes.   This fits exactly what we need.  The planned metadata is actually about the SD itself, so I want it to be written/erased along with the SD.  Thanks!