Invalid Application after SoftDevice DFU

Question

Hi, 
 
 I am using nRF52840, S140 V7.0.1. 
 I am using Secure Serial Bootloader and able to do DFU of Application. 
 
 Now I am trying to do the same for generating SoftDevice package. 
 Generate SoftDevice DFU package 
 nrfutil pkg generate --hw-version 52 --softdevice s140_nrf52_7.0.1_softdevice.hex --sd-req 0xCA --key-file private.key SoftDevice_V2_package.zip 
 
 I am trying to do SoftDevice DFU using below commands. 
 nrfutil dfu serial -pkg SoftDevice_V2_package.zip -p COM8 -b 115200 -fc 0 
 
 SoftDevice DFU is success. As per below link I am trying to understand the statement about Application invalidation. 
 
 “The application is retained during this process, but it might be invalid because of API changes in the SoftDevice, or because the new SoftDevice has a different size than the existing one. 
 https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsdk_nrf5_v16.0.0%2Flib_bootloader_dfu_banks.html&cp=6_1_3_5_1_2 
 
 1) Even after invalidating application, whether application will keep running. My application is running even after SoftDevice DFU. Does it mean application is not invalidated. 
 2) Whether we can't do application DFU after application getting invalidated. 
 3) How about version check. I did not give any version as part of command. 
 4) Whether the commands I used to generate package and doing SoftDevice DFU are fine. Please let me know if I miss anything. 
 
 Thanks & Regards 
 Vishnu Beema

Einar Thorsrud · Accepted Answer

Hi Vishnu, 
 1) Even after invalidating application, whether application will keep running. My application is running even after SoftDevice DFU. Does it mean application is not invalidated. 
 If the SoftDevice is of a different major version, then the SoftDevice and application will not be API compatible, and the application will be invalidated. If the API is compatible, the application will not be invalidated. In this case, it is not invalidated. 
 2) Whether we can't do application DFU after application getting invalidated. 
 If the application is invalidated the only way to get it running is to upgrade to a new application over DFU 
 3) How about version check. I did not give any version as part of command. 
 Version checking is used for application and bootloader, but not for SoftDevice. There is no option to add version number for the SoftDevice (though it has not been consistent for all SDK versions). This is not needed since the SoftDevice ID is always used. 
 4) Whether the commands I used to generate package and doing SoftDevice DFU are fine. Please let me know if I miss anything. 
 It should be fine. But just remember that if you update to a new major SoftDevice version you are forced to update the bootloader at the same time. For the application, it follows the earlier discussion. 
 Einar

Invalid Application after SoftDevice DFU

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