Hi,
We have been running into issues with our FOTA over BLE using mcuboot. Our usual process has been to use the dfu_application.zip file in the build/ directory (ncs v2.9.1) with nRF Connect for Mobile. For some reason, after some successful updates, our devices are now no longer able to being updated over the air. When going through the DFU process, the download step is skipped and the screen goes immediately to the validating screen. However, upon checking the firmware revision number, I can see that it's not changed. No apparent reason why the DFU failed though (no error message visible).
After doing some research, I installed the nRF Device Manager app to try again. This time I could see that the app indicates "No free slot (9)". Upon switching to 'advanced' and reading the images, I see that the second slot is set to
Bootable: TRUE
Pending: TRUE
Confirmed: FALSE
Active: FALSE
Permanent: TRUE
Compressed: FALSE
After reading the images, I see the Test and Confirm button greyed out (disabled) and the Erase button in red. However, pressing the erase button also results in a 'No free slot (9)' message. Sending the Reset Command or Power cycling the device doesn't help either. This happens on multiple devices (2 so far), although not on all.
Just to be clear, the device itself is functional, albeit at an older (buggy) firmware version. And it seems there's no way to erase the slot except for fully erasing the board, which is not practical as they are encapsulated. This post seems to indicate that using build/app/zephyr/zephyr.signed.bin is preferred for a DFU, but step 4 in the academy course seems to indicate that it should be fine working with the build/dfu_application.zip file as well.
What I'm wondering is, is it already clear what causes a slot to be marked as permanent (and staying that way even with power cycle/reset)? Is this also the reason that we are not able to erase the slot through the nRF Device Manager? And should using the zephyr.signed.bin instead of the zip file help to prevent this?
Do you know of another way to try and erase the slot without us having to break open the device enclosures?
Best,
Wout
