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circuitpython/ports/stm32/mboot/README.md

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Mboot - MicroPython boot loader

Mboot is a custom bootloader for STM32 MCUs, and currently supports the STM32F4xx and STM32F7xx families. It can provide a standard USB DFU interface on either the FS or HS peripherals, as well as a sophisticated, custom I2C interface. It fits in 16k of flash space.

How to use

  1. Configure your board to use a boot loader by editing the mpconfigboard.mk and mpconfigboard.h files. For example, for an F767 be sure to have these lines in mpconfigboard.mk:

    LD_FILES = boards/stm32f767.ld boards/common_bl.ld TEXT0_ADDR = 0x08008000

    And this in mpconfigboard.h (recommended to put at the end of the file):

    // Bootloader configuration #define MBOOT_I2C_PERIPH_ID 1 #define MBOOT_I2C_SCL (pin_B8) #define MBOOT_I2C_SDA (pin_B9) #define MBOOT_I2C_ALTFUNC (4)

    To configure a pin to force entry into the boot loader the following options can be used (with example configuration):

    #define MBOOT_BOOTPIN_PIN (pin_A0) #define MBOOT_BOOTPIN_PULL (MP_HAL_PIN_PULL_UP) #define MBOOT_BOOTPIN_ACTIVE (0)

    Mboot supports programming external SPI flash via the DFU and I2C interfaces. SPI flash will be mapped to an address range. To configure it use the following options (edit as needed):

    #define MBOOT_SPIFLASH_ADDR (0x80000000) #define MBOOT_SPIFLASH_BYTE_SIZE (2 * 1024 * 1024) #define MBOOT_SPIFLASH_LAYOUT "/0x80000000/64*32Kg" #define MBOOT_SPIFLASH_ERASE_BLOCKS_PER_PAGE (32 / 4) #define MBOOT_SPIFLASH_SPIFLASH (&spi_bdev.spiflash) #define MBOOT_SPIFLASH_CONFIG (&spiflash_config)

    This assumes that the board declares and defines the relevant SPI flash configuration structs, eg in the board-specific bdev.c file. The MBOOT_SPIFLASH2_LAYOUT string will be seen by the USB DFU utility and must describe the SPI flash layout. Note that the number of pages in this layout description (the 64 above) cannot be larger than 99 (it must fit in two digits) so the reported page size (the 32Kg above) must be made large enough so the number of pages fits in two digits. Alternatively the layout can specify multiple sections like 32*16Kg,32*16Kg, in which case MBOOT_SPIFLASH_ERASE_BLOCKS_PER_PAGE must be changed to 16 / 4 to match tho 16Kg value.

    Mboot supports up to two external SPI flash devices. To configure the second one use the same configuration names as above but with SPIFLASH2, ie MBOOT_SPIFLASH2_ADDR etc.

  2. Build the board's main application firmware as usual.

  3. Build mboot via:

    $ cd mboot $ make BOARD=

    That should produce a DFU file for mboot. It can be deployed using USB DFU programming via (it will be placed at location 0x08000000):

    $ make BOARD= deploy

  4. Reset the board while holding USR until all 3 LEDs are lit (the 4th option in the cycle) and then release USR. LED0 will then blink once per second to indicate that it's in mboot

  5. Use either USB DFU or I2C to download firmware. The script mboot.py shows how to communicate with the I2C boot loader interface. It should be run on a pyboard connected via I2C to the target board.