NRF9160 increase mcuboot secondary slot

[haraujo]

Hi,

We are using a NRF9160 alongside an NRF52840 chip to perform firmware updates for both.

We are using the NRF9160 AT_CLIENT sample app to run on NRF9160. Up until now, the firmware update process was working just fine.

Things turned south when NRF52840 firmware image reached a size bigger than 425984 bytes. We noticed that the NRF9160 at_client sample app does not allow transfers bigger than 425984bytes. Understandable due to the default mcuboot secondary slot size limit.

We tried changing/editing out the nrf9160 partitions via pm_static.yml file and increase the size limit to something like 0x72000 and 0x78000 bytes, but still didn't work.

We have a feeling that editing the partitions on a nrf9160 mcu is not very safe due to hardware/trustzone configurations.

This post's intention is to to know if anyone could please share here if he's ever faced this issue. And if so, could you please give a hint on how to do this properly? Like increasing flash size (what are the limitations knowing that we have trustzone/sau modules running)? Or changing a project config I am not aware? 

Thanks!

[Hakon]

Hello,

you can try to reduce the application memory footprint, as explained here. This will hopefully free up some memory.

[haraujo]

Hi Hakon,

Thank you for the reply. What if we've already made all possible memory optimizations and want to make use of the maximum capacity of nrf52840 flash? Is there a way to safely partition NRF9160 in order to match nrf52840's max size partitions?

We tried partitioning NRF9160 secondary's slot to a maximum size of 0x78000 bytes (same as NRF52840). But still something didn't work. We believe that there may have been a fault due to SAU/TrustZone.

In other words, I shall ask: Is it possible to extend the secondary slot partition on NRF9160 without interfering with SAU/SPU/TrustZone?

Thanks!

[Hakon]

haraujo said:

Is it possible to extend the secondary slot partition on NRF9160 without interfering with SAU/SPU/TrustZone?

You can try, the worst thing I can think of that can happen is the partition manager will give an error. Also, you can check how to optimize partition size here.