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stm32/N657X0: fix signing for Rev.B silicon and document flashing pro…#19290

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stm32/N657X0: fix signing for Rev.B silicon and document flashing pro…#19290
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@Mrpli

@Mrpli Mrpli commented Jun 1, 2026 •
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Summary

This pull request fixes mboot boot failures on NUCLEO-N657X0-Q boards with Rev B silicon. The STM32N657X0 chip has two silicon revisions that require different FSBL signing header versions:

  • Rev code Z (Cut 1.1) requires STM32_N6_HEADER_VERSION = 2.1
  • Rev code B (Cut 2.0) requires STM32_N6_HEADER_VERSION = 2.3

Currently mpconfigboard.mk defaults to 2.1, causing Rev B boards to fail booting after deploy-trusted. The signing header version is updated to 2.3 in this PR.

Additionally, STM32CubeProgrammer v2.21.0 and later no longer auto-align the binary payload to a 0x400-byte boundary. The --align flag has been added to the STM32_SigningTool_CLI invocation in both stm32/Makefile and stm32/mboot/Makefile; otherwise, the signing step fails with an alignment error and firmware-trusted.bin will not be generated correctly.

The board documentation (board.md) has been extended to cover:

  • How to select the correct header version for each silicon revision.
  • The --align requirement for STM32CubeProgrammer v2.21.0+.
  • An alternative ST-LINK flashing procedure for cases where the mboot USB DFU device does not enumerate on the host PC.

Testing

Hardware tested:

  • NUCLEO-N657X0-Q board with Rev B silicon (chip marking "B")

Test steps:

  1. Build mboot with updated configuration:
   make -C ports/stm32/mboot BOARD=NUCLEO_N657X0
  1. Deploy trusted image via ST-LINK (bypassing DFU):
STM32_Programmer_CLI -c port=SWD mode=HOTPLUG ap=1 \
  -el /opt/STM32CubeProgrammer/bin/ExternalLoader/MX25UM51245G_STM32N6570-NUCLEO.stldr \
  -w ports/stm32/mboot/build-NUCLEO_N657X0/firmware-trusted.bin 0x70000000 \
  -w ports/stm32/build-NUCLEO_N657X0/firmware.bin 0x70080000 \
  -hardRst
  1. Verify mboot activates:
  • Set CN9 to 3-4, JP2 to 1-2.
  • Connect USB cable to CN8.
  • Red LED2 should blink at 1 Hz, indicating mboot is active.
  • Host PC should detect a DFU device.
  1. Verify the --align fix:
    Without --align the signing step fails with an alignment error; with the flag added, firmware-trusted.bin is generated correctly.

Documentation:

  • Verified that board.md renders correctly and all added information is accurate.

Trade-offs and Alternatives

Defaulting to header version 2.3 means Rev Z (Cut 1.1) users must manually override with STM32_N6_HEADER_VERSION=2.1.However, Rev Z boards are no longer manufactured; all currently shipping boards use Rev B, so this change matches real-world hardware.

Alternatives considered:

1.Runtime header version detection:
The chip revision cannot be easily read before the FSBL is loaded, so build‑time selection is the only practical approach.

2.Using the USB DFU method only:
The DFU method relies on mboot being active, which fails on Rev B without the correct header version. The documented ST‑LINK alternative provides a fallback that works regardless of the mboot DFU state.

Generative AI

I used generative AI tools when creating this PR, but a human has checked the
code and is responsible for the code and the description above.

@github-actions

github-actions Bot commented Jun 1, 2026 •
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Code size report:

Reference:  samd/mphalport: Run events at least once in mp_hal_delay_ms. [af38ee1]
Comparison: stm32/n657x0: Remove STM32CubeProgrammer documentation section. [merge of 2ece331]
  mpy-cross:    +0 +0.000% 
   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
      esp32:    +0 +0.000% ESP32_GENERIC
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO_W
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:    +0 +0.000% VIRT_RV32

@Mrpli Mrpli force-pushed the fix-nucleo-n657x0-revb-mboot branch from f4f148f to 4e89504 Compare June 1, 2026 13:18
@Mrpli
stm32/n657x0: FIX Rev.B signing and add flash procedure.
1114402 
Signed-off-by: Mrpli <woe2468@outlook.com>
@Mrpli Mrpli force-pushed the fix-nucleo-n657x0-revb-mboot branch from 4e89504 to 1114402 Compare June 1, 2026 13:29
@kwagyeman

kwagyeman commented Jun 6, 2026

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Yeah, this is required.

dpgeorge
dpgeorge reviewed Jun 9, 2026
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Comment thread ports/stm32/boards/NUCLEO_N657X0/board.md Outdated

make -C ports/stm32/mboot BOARD=NUCLEO_N657X0 STM32_N6_HEADER_VERSION=2.3

## STM32CubeProgrammer v2.21.0 and later

@dpgeorge dpgeorge Jun 9, 2026

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I don't think this section about --align is needed. The relevant changes have been made to the code (and the commits serve as the history/documentation).

@Mrpli Mrpli Jun 9, 2026

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Thank you for the feedback! You're absolutely right – the --align flag is already in the code, and the commit history documents it well. I've removed that documentation section and kept only the chip revision guidance and ST-LINK flashing procedure. Updated in commit 2ece331.

@Mrpli Mrpli force-pushed the fix-nucleo-n657x0-revb-mboot branch 3 times, most recently from d46c3c4 to c635f97 Compare June 9, 2026 09:44
@Mrpli
stm32/n657x0: Remove STM32CubeProgrammer documentation section.
2ece331 
As suggested by the reviewer, the --align flag implementation is already
documented in the commit history. Remove the documentation section about
STM32CubeProgrammer v2.21.0 and later, while keeping the chip revision
and ST-LINK flashing procedure sections.

Signed-off-by: Mrpli <woe2468@outlook.com>
@Mrpli Mrpli force-pushed the fix-nucleo-n657x0-revb-mboot branch from c635f97 to 2ece331 Compare June 9, 2026 09:51
@Mrpli Mrpli requested a review from dpgeorge June 9, 2026 10:07
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