Discovery Kit N6570

The mboot bootloader must first be built and deployed to this board. Once its USB DFU port can be seen, the firmware below can be programmed as usual with any DFU loader.

Flashing mboot with ST-LINK

Make sure that JP2 is in position 1-2 to select STLK as the 5V power source, that SW2 (BOOT0) is set to 0 (left position) and SW1 (BOOT1) is set to 1 (right position). Then plug in a USB cable into the ST-LINK port CN6. This will allow mboot firmware to be programmed to the external SPI flash via ST's tools, eg:

make -C ports/stm32/mboot BOARD=STM32N6570_DK deploy-trusted

Once mboot is installed, change JP2 to position 3-4 to select USB as the 5V power source, change SW1 (BOOT1) back to 0 (left position) and change the USB cable to CN18. mboot will present a USB DFU device on this USB port, and the red LED2 should be blinking at 1Hz to indicate that mboot is active. If it's not active then hold the USER1 button and press NRST, and wait until both LEDs are on, then release USER1. Now mboot will be active.

Flashing mboot without ST-LINK

mboot can also be installed using only the STM32N6's own USB port, CN18, using the DFU mode of the chip's built-in bootloader (the boot ROM). Do not plug anything into the ST-LINK port CN6. Make sure that JP2 is in position 3-4 to select USB as the 5V power source.

First build the signed (trusted) mboot image, which the boot ROM requires. This needs STM32CubeProgrammer installed for its signing tool:

make -C ports/stm32/mboot BOARD=STM32N6570_DK build-STM32N6570_DK/firmware-trusted.bin

Then:

1. Set SW2 (BOOT0) to 1 (right position) and SW1 (BOOT1) to 0 (left position), then plug a USB cable into CN18. The boot ROM will enumerate over USB in DFU mode. The boot ROM also does this with SW2 set to 0 if the external SPI flash is empty.

2. Load mboot into RAM. The boot ROM can't write to the external SPI flash, but it can load mboot into RAM and run it:

   dfu-util -a 0 -D ports/stm32/mboot/build-STM32N6570_DK/firmware-trusted.bin -R
   

   mboot will present a USB DFU device on this USB port, and the red LED2 should be blinking at 1Hz to indicate that mboot is active. If MicroPython firmware is already in the external SPI flash, mboot will run it instead, so hold the USER1 button while loading mboot, wait until both LEDs are on, then release USER1.

3. Program mboot into the external SPI flash, using mboot's own DFU device:

   dfu-util -a 0 -s 0x70000000 -D ports/stm32/mboot/build-STM32N6570_DK/firmware-trusted.bin
   

4. Set SW2 (BOOT0) back to 0 (left position), leaving SW1 (BOOT1) at 0, and press NRST. mboot should run again just like before. If it's not active then hold the USER1 button and press NRST, and wait until both LEDs are on, then release USER1. Now mboot will be active.

Chip revision and signing header version

The STM32N657X0 chip is available in two silicon revisions, which require different signing header versions when building the trusted firmware image. Check the revision code printed on the chip package:

• Rev code Z (Cut 1.1): use STM32_N6_HEADER_VERSION = 2.1
• Rev code B (Cut 2.0): use STM32_N6_HEADER_VERSION = 2.3 (default in mpconfigboard.mk)

To override the version without modifying mpconfigboard.mk, pass it on the make command line:

make -C ports/stm32/mboot BOARD=STM32N6570_DK STM32_N6_HEADER_VERSION=2.3

Flashing mboot and firmware together via ST-LINK

If the DFU device is not recognised by the host PC on CN18 after mboot is installed, a reliable alternative is to program both mboot and the main MicroPython firmware directly via the ST-LINK interface in a single step. This bypasses DFU mode entirely and writes both images to the external SPI flash using STM32_Programmer_CLI:

STM32_Programmer_CLI \
  -c port=SWD mode=HOTPLUG ap=1 \
  -el <path-to-cubeprogrammer>/bin/ExternalLoader/MX66UW1G45G_STM32N6570-DK.stldr \
  -w mboot/build-STM32N6570_DK/firmware-trusted.bin 0x70000000 \
  -w build-STM32N6570_DK/firmware.bin 0x70080000 \
  -hardRst

Adjust <path-to-cubeprogrammer> to match the STM32CubeProgrammer installation on your system. The first -w programs the trusted mboot image at the start of the external SPI flash (0x70000000), and the second -w programs the main MicroPython firmware at 0x70080000 (512KB into the flash, immediately after mboot).

This approach works regardless of whether the USB DFU device enumerates correctly, and is especially useful on Rev code B boards where the signing header version or alignment settings may need to be adjusted first.

Installation instructions

STM32 via ST-Link

Nucleo and Discovery boards typically include a built-in ST-Link programmer.

A .bin or .hex file can be flashed using st-flash.

# Optional erase to clear existing filesystem.
st-flash erase

# Flash .bin
st-flash write firmware.bin 0x08000000
# or, flash .hex
st-flash --format ihex write firmware.hex

A .hex file can be flashed using STM32 Cube Programmer.

STM32_Programmer.sh -c port=SWD -d firmware.hex -hardRst

STM32 via DFU

Boards with USB support can also be programmed via the ST DFU bootloader, using e.g. dfu-util or pydfu.py.

To enter the bootloader the BOOT0 pin can be connected to VCC during reset, or you can use machine.bootloader() from the MicroPython REPL.

dfu-util --alt 0 -D firmware.dfu

Firmware

Preview builds

These are automatic builds of the development branch for the next release.