Bootloader reports "Image in the secondary slot is not valid" in MCXE31B

blessyvinolin — Thu, 12 Mar 2026 13:15:23 GMT

I am working on the NXP MCXE31B and using the MCUboot mcuboot_opensource example as the bootloader.

My goal is to implement OTA firmware updates by flashing the secondary slot via SPI using LPSPI in slave mode.

OTA Flow

The secondary firmware image is generated using the imgtool utility.
The image is transmitted from the SPI master in 256-byte chunks.
On the receiver side, the firmware receives the SPI data and writes it into the secondary slot using mflash_drv_page_program().
After the transfer is completed, the bootloader API boot_set_pending() is called to mark the image for swap.

Bootloader Behavior

After resetting the board, the bootloader prints the following log:

Bootloader Version 2.2.0

Image index: 0, Swap type: test

Image is invalid, erasing...

Image in the secondary slot is not valid!

Bootloader chainload address offset: 0x500000

Reset_Handler address offset: 0x500400

Jumping to the image

Image Header Verification

To verify the received image, I printed the MCUboot image header on the receiver side:

--- MCUboot Image Header Check ---

Magic: 0x96F3B83D (Expected: 0x96F3B83D)

Size: 20436 bytes

Version: 1.0.5+0

SPI Transfer Log

During SPI transfer, the firmware receives and writes the image successfully. The progress log shows the entire secondary slot being written:

Progress: 16384 / 786432 bytes

...

Progress: 786432 / 786432 bytes

Data transfer finished (786432 bytes).

After writing the data, the trailer is written and the image is marked as pending:

writing magic; fa_id=1 off=0xbfff0 (0x6bfff0)

writing swap_info; fa_id=1 off=0xbffd8 (0x6bffd8), swap_type=0x2 image_num=0x0

Success! Image marked. Resetting to trigger swap...

Flash Layout

Primary slot : 0x500000

Secondary slot : 0x600000

SPI Transfer Configuration

#define TRANSFER_SIZE 256

Issue

Even though:

The image header magic is correct
The image is generated using imgtool
The entire secondary slot is written successfully
The image is marked pending

The bootloader still reports that the secondary image is invalid.

Possible Causes Considered

I am currently investigating the following possibilities:

Incorrect image signing parameters
Mismatch between image size and slot size
Missing padding (--pad) during imgtool signing
Alignment issues with flash writes
Flash programming constraints when writing via mflash_drv_page_program()
Corruption of the MCUboot trailer area

Request

I would appreciate any suggestions or guidance on why MCUboot might reject the secondary image in this scenario and what additional checks I should perform to debug this issue.

Re: Bootloader reports "Image in the secondary slot is not valid" in MCXE31B

Alice_Yang — Tue, 17 Mar 2026 10:27:36 GMT

Hello @blessyvinolin

For using the mcuboot_opensource example, I highly recommend that you use MCUXpresso Secure Provisioning too.

https://www.nxp.com/design/design-center/software/development-software/mcuxpresso-software-and-tools-/mcuxpresso-secure-provisioning-tool:MCUXPRESSO-SECURE-PROVISIONING

Follow the steps described in

Secure Provisioning Tool User Guide 25.12 -> 7.5 MCUboot workflow .

Thank you.

Alice

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