pm_static optimize

[iibull]

Development environment:  ncs 2.6.0.  

my application need BLE-DFU, so i added multi-image support to my project. 

the pm_static.yml is the typical default system configuration

mcuboot:
  address: 0x0
  size: 0xc000
  region: flash_primary
mcuboot_pad:
  address: 0xc000
  size: 0x200
app:
  address: 0xc200
  size: 0x38e00
mcuboot_primary:
  orig_span: &id001
  - mcuboot_pad
  - app
  span: *id001
  address: 0xc000
  size: 0x39000
  region: flash_primary
mcuboot_primary_app:
  orig_span: &id002
  - app
  span: *id002
  address: 0xc200
  size: 0x38e00
mcuboot_secondary:
  address: 0x45000
  size: 0x39000
  region: flash_primary
settings_storage:
  address: 0x7e000
  size: 0x2000
  region: flash_primary

The results of my project compilation (-Os) are as follows

[240/248] Linking C executable zephyr\zephyr.elf
Memory region Used Size Region Size %age Used
FLASH: 208164 B 208384 B 99.89%
RAM: 59724 B 64 KB 91.13%
IDT_LIST: 0 GB 32 KB 0.00%

DFU work perfectly. 

BUT. as you see, the flash is full. <FLASH:      208164 B     208384 B     99.89%>, when I add some little source-code, the compile will prmot overflow-mistake. 

I found MCUBOOT just has 32K-size, 8KB settings-storage, and <mcuboot_primary> has 24KB nvs-storage.

I changed MCUBOOT-size to 40KB, or settings-storage to 4KB, compile will OK, but DFU failed.

my Question:

1. MCUBOOT-size changed to smaller feasible? Or the size can only be 0xC000=48KB?

2. i need settings-storage area, but the size can be smaller ?

3. nvs-storage=24KB Is it necessary? how to make it smaller ?

[iibull]

4.  <CONFIG_PM_PARTITION_SIZE_NVS_STORAGE couldn't be set. Missing dependencies:
!SETTINGS_NVS>, how to fixed this ?

[iibull]

i found the solution. CONFIG_PM_PARTITION_SIZE_NVS_STORAGE should be defined in mcu-boot.conf. then nvs-storage area size could be reduced to your defined size.

[AHaug]

Hi,

Starting with a couple of useful links w.r.t flash and RAM optimization:

1. https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/test_and_optimize.html
2.  Debunking misconceptions: A technical analysis of nRF5 SDK and nRF Connect SDK  

1. MCUBOOT-size changed to smaller feasible? Or the size can only be 0xC000=48KB?

Yes, smaller sizes are feasible. The default size is 48kB, while for instance all Matter samples in NCS uses MCUboot minimal configuration resulting in a MCUboot size of 24kB. In a general application it shouldn't be an issue to follow the steps to use a minimal MCUboot configuration.

2. i need settings-storage area, but the size can be smaller ?

Yes, you can define the size in your pm_static.yml and/or through https://docs.nordicsemi.com/bundle/ncs-latest/page/kconfig/index.html#CONFIG_PM_PARTITION_SIZE_SETTINGS_STORAGE as explained in https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/scripts/partition_manager/partition_manager.html#configuring_dynamic_partitions. Just be careful that you have a partition that is sufficiently large enough w.r.t how many connections you intend to have and other things you need/intend to store w.r.t settings

3. nvs-storage=24KB Is it necessary? how to make it smaller ?

The way you describe is correct in your replies is the correct way to do this. Same steps needs to be done for 2.

PS: Do also note that currently an application can't be larger than 95% of the MCUboot primary image, as this will violate the DFU procedure.

Kind regards,
Andreas