UART Bootloader - migrating from SD11 to SDK13

[PB]

Hello,

I've been using UART DFU feature quite extensively in one project which caused that I had to stick to SDK11 features (since bootloader relied on SD 132 2.0.0).

Recently, in SDK13 the UART DFU came back and after having experimenting with it it started working. Now I'd like to know what is Nordics suggested procedure to perform the switch from old to new bootloader+SD?

Neither the old bootloader and nrfutil 0.5.2 will accept the new FW package (BL+APP+SD) nor the nrfutil 3.2.0 will communicate properly with the old version of BL.

What is the Nordic suggested way to migrate if reflashing otherwise is not an option?

[bjorn-spockeli]

Hi PB,

the Secure Serial Bootloader is larger than the Legacy Serial Bootloader from SDK v11.0.0. If you're trying to update to the Secure Serial Bootloader then you're probably getting the REMOTE DFU DATA SIZE EXCEEDS LIMIT

This is because the new bootloader image must have the same start address as the old image, i.e. the new image cannot be larger than the old bootloader and if its smaller it must still have the same start address. This is because the bootloader start address is written to a UICR register, which the MBR jumps to during startup.

It is possible to workaround this using the approach described in this answer.

Best regards

Bjørn