Unknown bytes at several unused addresses after flashing firmware

[mbozic]

Hi!

Can't continue here:

https://devzone.nordicsemi.com/f/nordic-q-a/56211/bootloader-difference-and-implementation-from-sdk-14-to-sdk-16

So I've made a new question.

Thanks Einar for answering!

Using SDK16 and S132 with Segger Embedded Studio.

Managed to "ravage" the secure bootloader and create my own, so called "background bootloader". Still in development phase but according to my knowledge the thing should work.

I've managed to merge Softdevice, Application and Bootloader to a single hex file which we use for initial programming. And I have no problem starting the Bootloader and then switching to application, at least so far.

After flashing the file to nRF52832 I get 6  new locations in flash at which same 8 bytes of data can be found.

Address 0x7E000 (MBR PARAMS PAGE) is the only one which should be populated to some degree since I've removed bootloader settings section. My bootloader stores it's data in EEPROM.

I've attached 2 images with more explanation.

I've checked everything I could think of including Section Placement Macros and Memory Segments in SES but just can't find why are addresses 0x75000, 0x76000, 0x77000, 0x7D000 and 0x7F000 are populated with same pattern: DE C0 AD DE FE 01 1E F1.

Would like to know what they are, why are they there and how to remove them, if possible.

Thanks!

[Jørgen Holmefjord]

Hi,

What you are seeing is the Page tag of FDS. FDS is by default set to use 3 pages in most examples. These pages are initialized at run-time and are not included in the application HEX-file. If a bootloader is present, the FDS pages should be placed at the 3 pages right below the bootloader, otherwise at the top of the flash. If you do not explicitly use FDS in your application, it is also used by peer_manager library to store bonding data in flash. You did not say anything about how you flashed the chip, and if you erased it first, but I'm suspecting that you have previously run a non-bootloader application that utilizes FDS, and not preformed an "erase all" operation before flashing the application with bootloader merged? By default, only pages that contain data in the hex-file will be erased (section erase).

Best regards,
Jørgen

[mbozic]

Ah, great!

Example on which I built my application is using FDS. I'm not using it directly but it's included in the project.

Which is great because I though I have an error somewhere or doing something wrong. 

Thank you very much!

Br,

Mladen