How to boot from bank 1 or 2 / Dual Bank Flash / STM32L082

[JeroenIoT]

Hello,

I am trying to create code which is able to run from flash bank1 or from flash bank2 (using the dual bank STM32L0 architecture)

For this I am using platformio (stm32duino):

• In platformio.ini I created 2 environments (bank 1 and bank 2)

[env:STM32L082_bank1]
; no special options

[env:STM32L082_bank2]
extra_scripts = set_bank2.py
build_flags = -Wl,--defsym=LD_MAX_DATA_SIZE=0x5000 -Wl,--defsym=LD_MAX_SIZE=0x30000 -Wl,--defsym=LD_FLASH_OFFSET=0x18000

• For bank2 "set_bank2.py" script in order to change VECT_TAB_OFFSET:

Import("env")
offset = 0x18000 # offset from 0x8000000
env.Append(
    CPPDEFINES=[("VECT_TAB_OFFSET", "%s" % hex(offset))],
)
# remove old 0-offset, inject new one
linkflags = env["LINKFLAGS"]
linkflags = [x for x in linkflags if not str(x).startswith("-Wl,--defsym=LD_FLASH_OFFSET=")]
linkflags.append("-Wl,--defsym=LD_FLASH_OFFSET=%s" % hex(offset))
env["LINKFLAGS"] = linkflags 

• The generated BIN files are uploaded (bank1 to to 0x0800 0000 and bank2 to 0x0801 8000).
• Bank1 is running fine
• To run the code on bank2 I alter the OB BFB2 (using CUBEProgrammer)

However I do not get bank2 code running. Does anybody have suggestions or a code example for platformio (stm32duino based).

[fpistm]

Hi,
I never used DUAL bank. And don't know PIO.
you will probably have better support on PIO or stm32duino.com forums.
Maybe this AP can help: https://www.st.com/resource/en/application_note/an4767-onthefly-firmware-update-for-dual-bank-stm32-microcontrollers-stmicroelectronics.pdf

[ABOSTM]

@JeroenIoT,
Looking at Reference Manual:
RM0376 Rev 7 , paragraph 3.3.2 Dual-bank boot capability

• When the BFB2 bit is set and the boot pins are configured to boot from Flash memory
(BOOT0 = 0 and BOOT1 = x), the device maps the System memory at address 0. It
boots from the System memory after reset and Standby and executes (during
approximately 440 μs) the embedded bootloader code which implements the dualbank
boot mechanism:
a) The System memory code first checks Bank 2. If it contains a valid code (see note
below), it sets the UFB bit in SYSCFG_CFGR1 register to map Bank 2 at address
0x0800 0000, ...
...

Thus you binary for bank2 must be compiled and linked as if it is executed @0x08000000, so without offset 0x18000

[JeroenIoT]

Hi Alexandre,

Thanks for the feedback. Using VECT_TAB_OFFSET=0x18000 worked in the end for me, however it makes it a bit more complex as I have 2 different binary files (one for each bank).

So I started to test your suggestion. Unfortunately I could not get it working (yet) - below my results:

• Assumed BANK2 binary is identical to BANK1 binary
• Set LD_FLASH_OFFSET to 0x18000 (flash of BANK2 binary starts at 0x08018000)
• Checked banks after flashing: start (msp and pc) of bank1 and bank2 looks good
• However when swapping to BANK2 the code does not run (tried swap bank via app code and via CUBE Programmer - both had the same result).
• Below elf file of bank2 (which is identical to bank1 elf)

.pio\build\STM32L082_bank2\firmware.elf:     file format elf32-littlearm

Disassembly of section .isr_vector:

08000000 <g_pfnVectors>:
 8000000:       20005000        andcs   r5, r0, r0
 8000004:       080031f1        stmdaeq r0, {r0, r4, r5, r6, r7, r8, ip, sp}

Suggestions are appreciated :-)

[ABOSTM]

Hi @JeroenIoT ,
I made the following test which is working fine (which confirm the description from my previous post):

• I build a binary for bank1 (a blinky example)
• I program bank1 with this binary (using cube programmer), and it work fine
• I erase the whole flash (bank1 and bank2)
• without recompilation I program flash bank2 with the exact same binary (not the elf) using cube programmer
  This is the only step where I used a 0x18000 offset
  Of course it didn't work yet but ...
• .. I set BFB2 to 1 (cubeProgrammer) and then blinks worked again

I don't know about platformio.
I wonder whether it is a good thing in your setup to have LD_FLASH_OFFSET = 0x18000
as it impacts linker script (and thus linker stage),
For test purpose you can try to keep LD_FLASH_OFFSET =0 and to flash with cubeprogrammer.
Note: with Cube programmer bank2 is presented @0x18000 whatever BFB2 value

[JeroenIoT]

Hi Alexandre,

That is really interesting - I did the following

• Basic code to serialprint couple of lines
• LD_FLASH_OFFSET =0x0
• Generate BIN file
• Upload via CubeProgrammer to 0x08000000 (BFB2 = 0 )
• Serial prints are shown in serial monitor - ALL GOOD
• Now erase full flash
• Upload via CubeProgrammer to 0x08018000 and set BFB2 = 1 (see below)
• ... and there it ends. The code does not start to run from bank2

Do anybody have a sample bin with serial output? Would like to test it and understand why mine is not working with single BIN for both banks

[JeroenIoT]

I just found out that when I change the SystemInit(void) I can get it starting from bank2 (from system_stm32l0xx.c)

  /* Configure the Vector Table location add offset address ------------------*/
#if defined (USER_VECT_TAB_ADDRESS)
  //SCB->VTOR = VECT_TAB_BASE_ADDRESS | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal SRAM */
  //SCB->VTOR = 0x08018000UL;
#endif /* USER_VECT_TAB_ADDRESS */
  SCB->VTOR = 0x08018000UL;
  //SCB->VTOR = 0x08000000UL;
}

[ABOSTM]

I just remember,
there maybe a hardware bug depending on your hardware revision:
https://www.stm32duino.com/viewtopic.php?p=9512&sid=c7afedbe3211db4b141e89db1586af30#p9512

Can you check you hardware revision ?

[JeroenIoT]

I think my hardware version is revision Z.

Photo below and reading out register I get following information

• devID : 447
• revID : 2008

When reading the errata document I do not think it is my hardware version (afai can see)

Following from ST doc:

The following limitations are fixed in device revision Z:
• BFB2 bit does not select boot from Bank 2 system memory

[JeroenIoT]

Quick update

• I removed offsets and created 1 environment.
• When I add the SCB->VTOR = 0x08000000UL; to the end of the void SystemInit (void) the dual bank works
• In this case I generate a single BIN, flash it in both BANKs and it works good

So where is the SCB->VTOR normally set? In the original SystemInit(void) file it is not set and it works when using bank1 only.

@ABOSTM - how does the SystemInit() looks like for the stm32 processor you used in the test above? Was SCB->VTOR set?

[ABOSTM]

Yes it is done in at the end of void SystemInit (void)
but it is already done in latest version:

Arduino_Core_STM32/system/STM32L0xx/system_stm32l0xx.c

Line 174 in 75b051e

SCB->VTOR = VECT_TAB_BASE_ADDRESS | VECT_TAB_OFFSET;

So maybe you are not on latest version.
You you check with version 2.3.0 of Arduino_Core_STM32, or later ?

[JeroenIoT]

Great - that means my problem was tackled.:-)

• Yes I am using öld version - PIO is only at version STM32duino v2.2.0
• In this old v2.2.0 version the #if statements were not good when activating the dual bank.
• Tested the new conditions and it all works now
• So using the 2.3.0 version or alternatively one can add to the platformio.ini the following: build_flags = -D VECT_TAB_OFFSET=0x00000000U

Thanks a lot!