This is the documentation for the latest (main) development branch of mcuxpresso sdk. If you are looking for the documentation of previous releases, use the drop-down menu on the left and select the desired version.

ota_mcuboot_basic

Overview

This ota_mcuboot_basic example demonstrates a basic application that uses MCUBoot as a second stage bootloader.

Prepare the Demo

  1. The demo requires MCUBoot booloader to be present in the FLASH memory to function properly. It is recommended to build and program the bootloader first, then go on with the application. Please refer to respective readme of the mcuboot_opensource example and follow the steps there before you continue.

  2. Connect a USB cable between the PC and the Debug USB port on the target board.

  3. Open a serial terminal on PC for connected board with these settings:

    • 115200 baud rate

    • 8 data bits

    • No parity

    • One stop bit

    • No flow control

Transfering data to the flash memory

There are multiple ways how to transfer image updates to the flash memory:

  • This examples implements a simple XMODEM-CRC protocol, that can be used to transfer data to the board at slow speed (~10kB/s). This provides a convenient method for images that have relatively small size (under lower 100’s of kB). In the application shell the XMODEM receiving is initiated by xmodem command. Terminal emulators like Tera Term or ExtraPutty can be used as a transmitting side. Both 128B and 1024B packet sizes are supported.

  • An alternative way, more suitable for larger images, is to use the blhost utility (part of NXP’s SPSDK and MCUXpresso Secure Provisioning Tool). Blhost communicates with chip’s ROM and supports all basic flash operations. When used via onboard’s USB the transfer speed is more appropriate for larger files. See board’s user manual for details on ISP mode.

  • Another option is to use a debug adapter (e.g. JLink, CMSIS DAP…) and flash data using their tools.

Running the demo

To get the application properly executed by the bootloader, it is necessary to put signed application image to the primary application partition. There are multiple options how to achieve that, however in principle the are two main methods (both presuming the bootlaoder is already in place):

a) programing signed application image to the primary application partition using an external tool (direct method) b) jump-starting the application by debugger, performing an image update with the signed image, resetting the board and letting the bootloader to perform the update (indirect method)

The latter method is used in the following step-by-step description:

  1. Open the demo project and build it. Known issue: MDK linker issues warning about unused boot_hdr sections. This does not affect the functionality of the example.

  2. Prepare signed image of the application from raw binary as described in the readme of mcuboot_opensource SDK example.

    • In case of MCUXpresso raw binary may not be generated automatically. Use binary tools after right clicking Binaries/.axf file in the project tree to generate it manually.

  3. Launch the debugger in your IDE to jump-start the application.

    • In case of MCUXpresso IDE the execution stalls in an endless loop in the bootloader. Pause the debugging and use debugger console and issue command jump ResetISR.

  4. When the demo starts successfully, the terminal will display shell prompt as in the following example:

    *************************************
* Basic MCUBoot application example *
*************************************

Built Feb 22 2024 13:09:14

$

  5. Available commands can be printed with help command

  6. Current image state is printed with image command. The output will reflect settings of the used platform and may not be exactly the same as the following output:

    $ image
Image 0; name APP; state None:

  Slot 0 APP_PRIMARY; address 0x20000; size 0x30000 (196608):
    <No Image Found>

  Slot 1 APP_SECONDARY; address 0x50000; size 0x30000 (196608):
    <No Image Found>

  7. From the shown image command output it can be observed that there are currently no signed images present neither in the primary nor the secondary slot. Since the example was started by a debugger, it is not signed and hence not recognized as a valid signed image in the primary slot.

  8. Before an image update can be downloaded using the xmodem command, the secondary image slot needs to be erased:

    $ image erase

  9. XMODEM transfer is initiated using xmodem command. When executed, it starts waiting for the transmitting side. In this demonstration Tera Term is used to send the update file. The dialog File->Transfer->XMODEM is used to select a file to be send. In the same dialog a packet size can be extended to 1kB for faster transmittion.

    $ xmodem
Initiated XMODEM-CRC transfer. Receiving... (Press 'x' to cancel)
CCC
Received 31744 bytes
SHA256 of received data: 547251A815E1DFB074F9...
SHA256 of flashed data:  547251A815E1DFB074F9...

  10. After image downloaded finished the current image status can be checked with image command. The output now shows that there is an MCUBoot image file detected in the secondary slot. The SHA256 digest is different from the digest computed for the data downloaded via XMODEM. This is because XMODEM protocol pads data at the end to make their size multiple of the packet payload size (128/1024 bytes).

    $ image
Image 0; name APP; state None:

  Slot 0 APP_PRIMARY; address 0x20000; size 0x30000 (196608):
    <No Image Found>

  Slot 1 APP_SECONDARY; address 0x50000; size 0x30000 (196608):
    <IMAGE: size 30352; version 2.2.0+0>
    SHA256 of image payload: 918A708203EE4AD7C616...

  11. To let the bootloader install the new image it must be marked as ReadyForTest. This is done using image test command. After running this command the result can be checked by runnig the image command again.

    $ image
Image 0; name APP; state ReadyForTest:
...

  12. Running reboot command or resetting the board manually starts the bootloader and lets it handle the installation of new image. If everything went well the image from the secondary slot was moved to the primary slot and the bootloader started its execution. The image command output should reflect this change:

    $ image
Image 0; name APP; state None:

  Slot 0 APP_PRIMARY; address 0x20000; size 0x30000 (196608):
    <IMAGE: size 30352; version 2.2.0+0>
    SHA256 of image payload: 918A708203EE4AD7C616...

  Slot 1 APP_SECONDARY; address 0x50000; size 0x30000 (196608):
    <No Image Found>

  13. If the bootloader was configured to use the image swapping mode, another image can be now downloaded to test this. The process is exactly the same as in the previous steps. The only difference will be after the image is installed because this time the image state will be set as Testing. In this state the newly running image must confirm itself otherwise the booloader will revert back to previous image on the next reboot. The confirmation is done by image accept command after which the image state will be set as None.

Supported Boards