Hardware requirements

  • Micro USB cable

  • FRDM-MCXN947 board

  • Personal Computer

Board settings

MCUBoot layout for the internal flash

Region

From

To

Size

MCUboot code

0x01008000

0x0100FFFF

32kB

Primary slot

0x00000000

0x000FFFFF

1024kB

Secondary slot

0x00100000

0x001FFFFF

1024kB

  • MCUBoot resides in the Bank_1 IFR_0 region

  • MCUBoot header size is set to 1024 bytes

  • Signing algorithm is ECDSA-P256

  • Write alignment is 16 bytes

  • MCUBoot is configured to use its DIRECT_XIP image handling strategy

  • Flash swapping HW feature is used for zero-overhead image swapping

Image signing example:

imgtool sign --key sign-ecdsa-p256-priv.pem
             --align 16
             --version 1.1
             --slot-size 0x100000
             --header-size 0x400
             --pad-header
             ota_mcuboot_basic.bin
             ota_mcuboot_basic.SIGNED.bin

Note that for the first image flashed manually together with the bootloader additional imgtool options --pad and --confirm must be used. Otherwise the bootloader would reject the image for missing data in the trailer area.

If the toolchain used for build has problems with writing the bootloader to the IFR flash region, an alternative can be to use NXP blhost utility or MCUXpresso Secure Provisioning Tool.

IMPORTANT: The CMPA region must be configured so that ROM loader boots from the IFR region. This is done by setting the BOOT_CFG.BOOT_SRC field to 0b10. This value directs the ROM loader to start execution from the IFR region where MCUboot is located. Default CMPA setup with this particular field set is attached to this example in cmpa.bin binary file. To flash this configuration together with MCUboot binary the following blhost commands can be used. Note that the board must be in the ISP mode to use the following commands:

#Erase IFR0 Bank 1 region
blhost -u 0x1FC9,0x014F -- flash-erase-region 0x01008000 32768 0

#Flash MCUboot
blhost -u 0x1FC9,0x014F -- write-memory 0x01008000 mcuboot_opensource.bin

#Flash CMPA
blhost -u 0x1FC9,0x014F -- write-memory 0x01004000 cmpa.bin