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Zephyr project on STM32

   Zephyr Workbench, a VSCode extension to manage Zephyr on STM32.
It enables users to easily create, develop, and debug Zephyr applications.
Main features:
  • Install host dependencies.
  • Import toolchain and SDK.
  • Create, configure, build and manage apps.
  • Debug STM32.
You can directly download it from the VSCode marketplace
For more details, visit the Zephyr Workbench

System Workbench for STM32

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stack pointer initialization

Posted by erwin78 on 2019-05-08 11:50

Hi,

I’m pretty new to ARM processor and STM32 microcontroller, so my question is very basic.
In the startup file for a SW4STM32 project (eg startup_stm32f446xx.s) the stack pointer is set in Reset_Handler with the line

ldr sp, =_estack /* set stack pointer */

Why is this needed? I mean as far as I know the ARM Cortex-M is fetching automatically the value of the stack pointer as first step during the booting sequence. Why has it to be done a second time via software? It looks like it is initialized twice to the same value (_estack) since the vector table has the form:

.word _estack
.word Reset_Handler
.
.
.

Reads: 8007
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Posted by pramod on 2020-03-02 16:57
Sometimes SP may not be pointing to the end of the stack on bootup. So the instruction “ldr sp, =_estack” /* set stack pointer */ will forcefully set the SP to end of the stack. I found this behavior in STM32F103VEt MCU whose code was generated by using CubeMx. The expected stack pointer register value on startup was “0x20005000” but the value found in the SP was “0x200001FC”.
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