NCS BLE Project using too much flash

[dlewis]

Hi All,

I am looking for assistance with trying to reduce flash usage of my project. 
I am using NCS v2.6 with an nRF52832.

Attached is my prj.conf file. The major SDK features being used are:
- BLE
- DIS and BAS services
- 1 custom BLE service
- Extended advertising
- PWM Leds
- SAADC for battery measuring
- MCUboot for OTA
- Crypto functionality

My prj.conf already includes many of the configuration suggestions from Memory Optimization with the nRF Connect SDK - Software - nRF Connect SDK guides - Nordic DevZone (nordicsemi.com) and the minimal prj.conf, but the flash usage exceeds the available size by a few kb. I've noticed that enabling extended advertising alone adds about 34kb of flash usage which seems excessive. I am currently running under the premise that I cannot remove any of the major features in order to reduce memory usage. Any tips or advice would be greatly appreciated, thanks! 
5078.prj.conf

[Amanda Hsieh]

Hi, 

You also can take a look at the Memory footprint optimization doc. If you already did all to optimize, but still get size overflow. You might consider using an external flash as the secondary slot for BLE DFU or another nRF Chips with larger internal memory. 

Regards,
Amanda H.

[dlewis]

Hi Amanda, I have referenced that document. It has a fair bit of overlap with the devzone guide I linked. Unfortunately, adding additional flash is not an option. The hardware is being supplied by the customer and has no option to use a different chip with more flash or add external flash. 

[Amanda Hsieh]

Then, you has to consider disable some features or reduce the overall number and the sizes of the Bluetooth buffers. 

[dlewis]

Hi, I've gone through and disabled as many features as I can as well as reducing the buffers to the minimum amounts allowable for the specific project. The amount of additional space saved was less than 50 bytes. Do you know why extended advertising uses an additional 34kb? Is there any ways to reduce this? I am only using about 40 bytes in my advertising data and don't need all 1650, but setting 

CONFIG_BT_CTLR_ADV_DATA_LEN_MAX=40
only reduced the flash usage by 1 byte. 

[Amanda Hsieh]

Hi, 

Extended Advertising allows for more flexible and robust advertising scenarios. This includes support for larger payloads, which can increase the amount of data that can be broadcasted in a single advertising event and could potentially explain the increased memory usage. 

Besides the Memory footprint optimization doc, I don't have extra suggestions for Extended Advertising.  

-Amanda H.