Softdevice 7 does not boot unless flash space gap is filled 0xFF

[hjz]

Recently tried to upgrade the NRF SDK from 14 to 16 on our project, and also upgrading Softdevice from 5.0.1 to 7.0.0.

While trying to bring up Softdevice 7.0.0, we noticed that the main FW will NOT get booted unless all the gaps in the flash space filled with 0xFF instead of 0x00.

We discovered this because in our flash script we merge the hex files of softdevice and main FW, and then convert them to a binary file using arm-objcopy, and by default arm-objcopy fills any gap space from the hex file with 0x00.

This process worked fine on Softdevice 5.0.1 with NRF SDK 14, but now fails with Softdevice 7.0.0 and NRF SDK 16. Only when arm-objcopy used with gap-fill 0xFF option did Softdevice and main FW boot up properly.

We just want to confirm this is the desired behaviour, and wondering what changed since SDK 14 and Softdevice 5.0.0 that caused this behviour?

[Amanda Hsieh]

Hi, 

From SDK v15.3 we changed the bootloader start address register (NRF_UICR_BOOTLOADER_START_ADDRESS) from NRF_UICR_BASE + 0x14 in the UICR to MBR_BOOTLOADER_ADDR (at 0xFF8) in the MBR. 

Please see this post and this. 

-Amanda H.

[hjz]

Thanks Amanda, this seems to be issue. Confirmed this by manually editing the MBR_BOOTLOADER_ADDR.