Reduce nRF7002dk image size

[esisk]

Hello, I'm in the development stage of a product and currently evaluating the nRF5340 as our main processor and nRF7002 as a companion IC for WiFi. Our application can be used in a wide variety of connectivity environments, so we require a WiFi interface, Ethernet interface, a cellular/GPS modem, and BLE. Also, we want to make MQTTS/HTTPS connections to our cloud provider. I've gotten a lot of these individual components to work individually by building our app to run on a nRF7002dk; however, I'm running into issues with the size of the image being too big when I try to include all of the necessary config variables in my build. Is what I'm attempting to do infeasible? My current build is overflowing RAM by 71,272 bytes and Flash is overflowed by 10,160 bytes. I can share my board overlays and configuration files. To be clear, I'm using NCS version 2.8.0, and building an application with nrf/7002dk/nrf5340/cpuapp/ns board as the target.

4336.prj.conf sysbuild.conf 3731.nrf7002dk_nrf5340_cpuapp_ns.conf nrf7002dk_nrf5340_cpuapp_ns.overlay

[BrianW]

Elfving said:

different memory requirements of some of the features

Thanks for these links. in fact its this one that is most relevant to my product case:

https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/protocols/wifi/station_mode/mem_requirements_sta.html

And it dfoes indeed show that for a wifi application in STA mode with WPA2 using MQTT, the most basic ROM size is 702kB (out of the 960kB available when using mcuboot)! (not to mention the 320kB of RAM from the 440kB available!)

Now, this is the sample which makes no effort to limit the memory usage, and by disabling bits I don't need I can trim it - but this is where the difficulty with the doc comes in. An example:

CONFIG_MBEDTLS_ECP_C=n

should avoid using the EC crypto code which I don't need : but somehow the base nrf-security config always overwrites this to y and enables all that stuff! Any ideas on how to disable this?

I also note it needs 73kB for the wifi patches (in fact 128kb if you want to do DFU on them), and these can be placed in an external XIP flash. Do you have a known good config (prj.conf and partition setup/init) example for this?

[Elfving]

BrianW said:

should avoid using the EC crypto code which I don't need : but somehow the base nrf-security config always overwrites this to y and enables all that stuff! Any ideas on how to disable this?

Hmm, this seems to be selected by a few other configs that it is worth checking if you have enabled. It might be that this config is needed, and it might rather pay of disable some other features that are selected by it.  Do you get any sort of error message or anything regarding it not being disabled?

BrianW said:

I also note it needs 73kB for the wifi patches (in fact 128kb if you want to do DFU on them), and these can be placed in an external XIP flash. Do you have a known good config (prj.conf and partition setup/init) example for this?

This page goes a bit into that. 

Regards,

Elfving

[BrianW]

Elfving said:

Hmm, this seems to be selected by a few other configs that it is worth checking if you have enabled. It might be that this config is needed, and it might rather pay of disable some other features that are selected by it.  Do you get any sort of error message or anything regarding it not being disabled?

No error messages, it just doesn't get disabled. Shouldn't the build system flag that I have selected a build option explicitly in my config that was not taken into account?

As for the other configs, the one that is selected is about WPA supplicant:

• CONFIG_WIFI_NM_WPA_SUPPLICANT_CRYPTO
• CONFIG_WIFI_NM_WPA_SUPPLICANT_CRYPTO_ALT

Is is not possible to select what crypto I want for the WPA supp operation? I think I have managed to already cut does the size of this blob by deselecting things I can do without (WEP, WPA-Enterprise etc)... and I don't think that EC crypto is required for WPA2-PSK at all.... 

[BrianW]

not an error message, but it does say:

warning: MBEDTLS_ECP_C (defined at C:/ncs/v2.8.0/nrf\modules/trusted-
firmware-m/Kconfig.mbedtls_minimal.defconfig:41,
C:/ncs/v2.8.0/nrf\subsys\nrf_security\Kconfig.legacy:557,
C:/ncs/v2.8.0/zephyr/modules/mbedtls\Kconfig.tls-generic:157, modules\mbedtls\Kconfig.tls-
generic:157) was assigned the value 'n' but got the value 'y'. See
docs.zephyrproject.org/.../kconfig.html and/or look up MBEDTLS_ECP_C
in the menuconfig/guiconfig interface. The Application Development Primer, Setting Configuration
Values, and Kconfig - Tips and Best Practices sections of the manual might be helpful too.

which is a lot of blah for not much actual help.

I tried setting 

CONFIG_WIFI_NM_WPA_SUPPLICANT_CRYPTO=n

but this seems to have no effect (no warning, no error, wpa-supp still works for WPA2, code size is not reduced, ECP is still compiled in...

[Elfving]

Hi Brian, and sorry about the wait. 

BrianW said:

CONFIG_WIFI_NM_WPA_SUPPLICANT_CRYPTO=n

but this seems to have no effect (no warning, no error, wpa-supp still works for WPA2, code size is not reduced, ECP is still compiled in...

The configuration system can be a bit confusing at times, some configs might select certain others, making it difficult to deselect them if you don't know what is selecting what. We can look into this, but as this issue is progressing a bit beyond OPs original issue, it might be best if you could open a new case with this problem. We prefer to get the tickets focused on one issue.

Regards,

Elfving