S132 v5.1.0 for nRF52810 has excessive flash requirements

[thcooke77]

The flash requirements for both the S132 v5.0.0 and v5.1.0 are the same, however the size of the v5.1.0 softdevice is quite a bit smaller.

S132 v5.0.0 uses flash addresses 0x1000 to 0x224A8 with the application start address specified as 0x23000.  This makes perfect sense.

S132 v5.1.0 uses flash addresses 0x1000 to 0x1F084 but with the application start address still specified as 0x23000.  What happened to the extra 0x3000 of flash space?  This is a significant amount of wasted flash for an already flash constrained MCU.  Is there any way to recover this?  Is this space being utilized differently than the v5.0.0?

[Amanda Hsieh]

Hi,

  

    The flash setting will be different according to the SoftDevice version. Plesae refer to this page.

Best regards,

Amanda

[thcooke77]

Amanda, I appreciate the link, however, I am asking about the difference between 5.0.0 and 5.1.0.  S132 v5.1.0 is not listed on that page.  The flash settings I described are contained in the release notes of the respective softdevice.  The discrepancy is in the actual size of the softdevice.

I understand this sounds like a less experienced question, however, this is not the case.  This will likely need to be addressed by Nordic, or at least explained why I'm unable to use 0x3000 bytes of flash.  This is basically the difference between being able to update the application via DFU and not, which is a really big deal.

[Amanda Hsieh]

The difference in flash between 5.0 and 5.1 is due to code refactoring and optimization. 

The start address is the same, in order to keep them binary compatible i.e. all versions of the 5.x have the same start address

Usually it's the other way around, i.e. a new minor version uses slightly more flash. Therefore we reserve some space below the start address, so that we can release new minor versions that are binary compatible with the old version and keep the start address constant. This is also beneficial for softdevice only DFU.

-Amanda

[thcooke77]

That generally makes sense, however this softdevice was released specifically to work on the small flash nRF52810. Allocating a large amount of flash to blank space because that's what is generally done seems like a poor choice.

I hope that Nordic reconsiders their stance or at least offers a variant that deallocates that space for the softdevice and gives it back to the developer.

[Amanda Hsieh]

Thanks for the suggestion. I will report to the development team.