Search code examples
stm32platformiostm32f0

Where are the files defining NVIC for STM32 in PlatformIO when using CubeMX?

I've recently switched to using PlatformIO for developing for STM32 using the following workflow:

  • Create a .ioc file using the CubeMX utility
  • Generate source code and the PlatformIO configuration from that .ioc file from the stm32pio command line utility
  • Edit, build, and debug using the PlatformIO plug-in for VSCode (Mac)

Overall, this works very well. However, I was previously using the CubeMX code generation in ST's CubeMX IDE, which placed a .s file in the source directory that (as I understand it) defined the NVIC, as well as the default function that was used for exceptions/interrupts that are not explicitly defined (i.e., those handled by their default weak implementations.) I don't see where this is defined in the new workflow. Is this generated dynamically as part of the build process?

The reason I'm asking is (beside wanting a better understanding of the process overall), I'd like to write an interrupt handler for EXTI0, but trigger it as a software interrupt, and not assign a pin to it. If that is not possible, then perhaps the entire point is moot.

Solution

  • I was able to find the answer. These steps might be useful to somebody else who comes across this question. This was done on MacOS, but should be similar to the process for other operating systems.

    During the build process, the filename can be seen. It will be prefaced with startup_, followed by the name of the particular chip you're developing for. In my case, the line is

    Compiling .pio/build/disco_f072rb/FrameworkCMSISDevice/gcc/startup_stm32f072xb.o

    Searching in the .platformio folder of my user directory, I found the matching .s file, which in my case was .platformio/packages/framework-stm32cube/f0/Drivers/CMSIS/Device/ST/STM32F0xx/Source/Templates/gcc/startup_stm32f072xb.s

    The structure of the path leading to the file indicates the particulars of the hardware and frameworks I'm using: STM32Cube framework, a F0 series chip, and the GCC compiler. The easiest way to find this file, and how I was able to find it, is using the find command from the terminal to search the PlatformIO directory.

    Reading this file gives the lines I was looking for, defining the names of the functions to be used for exception and interrupt handling, such as the following:

    .weak      EXTI0_1_IRQHandler
.thumb_set EXTI0_1_IRQHandler,Default_Handler

    It seems like, while I am using the CubeMX HAL for some drivers, the basic startup code is done using CMSIS, so it should be the same for HAL, LL, or CMSIS based builds.