ke7c2mi
ke7c2mi
PostsComments
DIIDevHeads IoT Integration Server
Created by Sterling on 9/11/2024 in #firmware-and-baremetal
How to Manually Program an Interrupt Service Routine (ISR) for STM32F4 MCU Without Using Libraries?
But how do we define that table? Well we can see how ST do it here: https://github.com/STMicroelectronics/cmsis_device_f4/blob/master/Source/Templates/arm/startup_stm32f401xc.s 
; Vector Table Mapped to Address 0 at Reset
                AREA    RESET, DATA, READONLY
                EXPORT  __Vectors
                EXPORT  __Vectors_End
                EXPORT  __Vectors_Size

__Vectors       DCD     __initial_sp               ; Top of Stack
                DCD     Reset_Handler              ; Reset Handler
                DCD     NMI_Handler                ; NMI Handler
....
; Vector Table Mapped to Address 0 at Reset
                AREA    RESET, DATA, READONLY
                EXPORT  __Vectors
                EXPORT  __Vectors_End
                EXPORT  __Vectors_Size

__Vectors       DCD     __initial_sp               ; Top of Stack
                DCD     Reset_Handler              ; Reset Handler
                DCD     NMI_Handler                ; NMI Handler
....
This is startup code, we see the table of vectors being declared at line 60, but that's only half the story, we should also look at the linker file: https://github.com/STMicroelectronics/STM32CubeF4/blob/master/Projects/STM32446E-Nucleo/Templates/STM32CubeIDE/STM32F446RETX_FLASH.ld This is where the table actually gets placed at a specific location: 
  /* The startup code into "ROM" Rom type memory */
  .isr_vector :
  {
    . = ALIGN(4);
    KEEP(*(.isr_vector)) /* Startup code */
    . = ALIGN(4);
  } >ROM
  /* The startup code into "ROM" Rom type memory */
  .isr_vector :
  {
    . = ALIGN(4);
    KEEP(*(.isr_vector)) /* Startup code */
    . = ALIGN(4);
  } >ROM
In English - put the symbol ".isr_vector" at the start of the ROM section - which is flash - which is where our table should be on startup ... we're still not done yet...
9 replies