MCUXpresso SDK Documentation
Open on Repo Open an Issue
Source (.md/.rst) Page PDF (.pdf)

Hardware requirements

Hardware requirements#

  • Micro USB cable

  • FRDM-MCXN236 board

  • Personal Computer

Board settings#

Default MCUBoot memory layout - bootloader located in IFR region#

Region

From

To

Size

Primary slot

0x00000000

0x0007FFFF

512kB

Secondary slot

0x00080000

0x000FFFFF

512kB

—————-

————

————

——-

MCUboot code

0x01008000

0x0100FFFF

32kB

  • MCUBoot resides in the Bank_1 IFR_0 region to utilize flash remap feature

  • MCUBoot header size is set to 1024 bytes

  • Signing algorithm is ECDSA-P256 (TinyCrypt)

  • 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

  • To manually enter serial recovery mode, keep the SW2 button pressed during reset, then release it

Image signing example:

imgtool sign --key sign-ecdsa-p256-priv.pem
             --align 16
             --version 1.1
             --slot-size 0x80000
             --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 0x1FC9,0x0158 -- flash-erase-region 0x01008000 32768 0

#Flash MCUboot
blhost -u 0x1FC9,0x0158 -- write-memory 0x01008000 mcuboot_opensource.bin

#Flash CMPA
blhost -u 0x1FC9,0x0158 -- write-memory 0x01004000 cmpa.bin

To flash signed application using blhost you can use the following:

#Erase first application slot
blhost -u 0x1fc9,0x0158 -- flash-erase-region 0 0x80000 0

#Flash signed application (must be signed with --pad --confirm flags)
blhost -u 0x1FC9,0x0158 -- write-memory 0 ota_mcuboot_basic.N236.SIGNED.PADDED.bin

Alternative MCUBoot memory layout - bootloader located in the main memory#

It is also possible to have the bootloader occupy the main memory. This allows for larger memory footprint compared to IFR region (32kB). However the flash remapping (swapping) feature becomes difficult to use in this configuration. For more details about this mode see MCUboot example for MCXN947 board where both the default IFR scheme and this alternative one are implemented.

Contents