Entering a bootloader (ST system bootloader, or custom mboot) from software
by directly branching to it is not reliable, and the reliability of it
working can depend on the peripherals that were enabled by the application
code. It's also not possible to branch to a bootloader if the WDT is
enabled (unless the bootloader has specific provisions to feed the WDT).
This patch changes the way a bootloader is entered from software by first
doing a complete system reset, then branching to the desired bootloader
early on in the start-up process. The top two words of RAM (of the stack)
are reserved to store flags indicating that the bootloader should be
entered after a reset.
Previously the end of the heap was the start (lowest address) of the stack.
With the changes in this commit these addresses are now independent,
allowing a board to place the heap and stack in separate locations.
If the board-pin name is left empty then only the cpu-pin name is used, eg
",PA0". If the board-pin name starts with a hyphen then it's available as
a C definition but not in the firmware, eg "-X1,PA0".
The alternate function pin allocations are different to other NUCLEO-144
boards. This is because the STM32F413 has a very high peripheral count:
10x UART, 5x SPI, 3x I2C, 3x CAN. The pinout was chosen to expose all
these devices on separate pins except CAN3 which shares a pin with UART1
and SPI1 which shares pins with DAC.
Includes:
- Support for CAN3.
- Support for UART9 and UART10.
- stm32f413xg.ld and stm32f413xh.ld linker scripts.
- stm32f413_af.csv alternate function mapping.
- startup_stm32f413xx.s because F413 has different interrupt vector table.
- Memory configuration with: 240K filesystem, 240K heap, 16K stack.
This patch makes pllvalues.py generate two tables: one for when HSI is used
and one for when HSE is used. The correct table is then selected at
compile time via the existing MICROPY_HW_CLK_USE_HSI.
To use HSI instead of HSE define MICROPY_HW_CLK_USE_HSI as 1 in the board
configuration file. The default is to use HSE.
HSI has been made the default for the NUCLEO_F401RE board to serve as an
example, and because early revisions of this board need a hardware
modification to get HSE working.
This demonstrates how to use external QSPI flash in XIP (execute in place)
mode. The default configuration has all extmod/ code placed into external
QSPI flash, but other code can easily be put there by modifying the custom
f769_qspi.ld script.
This is a good board to demonstrate the use of Mboot because it only has a
USB HS port exposed so the native ST DFU mode cannot be used. With Mboot
this port can be used.
The pin alternate function information is derived from ST's datasheet
https://www.st.com/resource/en/datasheet/stm32l432kc.pdf
In the datasheet, the line 2 of AF4 includes I2C2 but actually the chip
does not have I2C2 so it is removed.
The macros are MICROPY_HEAP_START and MICROPY_HEAP_END, and if not defined
by a board then the default values will be used (maximum heap from SRAM as
defined by linker symbols).
As part of this commit the SDRAM initialisation is moved to much earlier in
main() to potentially make it available to other peripherals and avoid
re-initialisation on soft-reboot. On boards with SDRAM enabled the heap
has been set to use that.
