status of SRAM during an over the air update

[weightwatcherphil]

The project I am working on stores information in SRAM while it waits for the radio to get in range and transmit data.

I want to know if I can put items in SRAM buffer that will remain there during an over the air firmware update.

I will not change the boot loader.  I am concerned there might be a reset during the over the air update that

will invalidate the contents of all SRAM.

[Vidar Berg]

Hi,

The DFU process involves system resets (soft), but this does not reset RAM (reset behavior). It is in other words possible to retain the data through DFU given that the data is kept in a non-initialized section of the RAM.  This will require changes in the linker configuration for both application and bootloader. I can provide instructions on how to declare a non-initialized  RAM section if needed, just need to know which toolchain you are using.  

[weightwatcherphil]

I am using the Segger Embedded Studio on the nRF52840 development board

thanks

[Vidar Berg]

You can use the __attribute__ keyword in your code to place a variable in the non_init section:

static uint8_t data[SIZE] __attribute__((section(".non_init")));

Then you need to edit the flash_placement.xml (located in same directory as project file) to ensure the .no_init section is placed in an area of RAM that is not already used by the bootloader or application:

<ProgramSection alignment="4" load="No" name=".non_init" start="START_ADDRESS" size="SIZE"/>

[weightwatcherphil]

thank you