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How to build an application for dual core(M4+M0) MCU?

Hello

I'm using Cortex-M3, and because of speed and peripherals, I want to use a dual core MCU.

I realized I have to write two separate code and make two separate executable file.

But I don't know how to merge these executable files.

I have to write down the executable files in separate specific region of flash?

Can anyone help me? I'm a little confused

Thank you

Parents
  • As allenwillson already mentioned, you can build two different executables:

    1. A Cortex-M0 executable
    2. A Cortex-M4 executable

    You convert the Cortex-M0 executable to a hex-file and from your Cortex-M4 code, you load the image and start the Cortex-M0 core.

    But there is a different way, which has not been covered in any documentation I know of.

    I write all the code in assembly language; sometimes I write some files in C for the Cortex-M4, though.

    But I write the Cortex-M0 code in assembly language, and I use GCC and GAS for building my project.

    I recommend that the first line of your assembly file is...

                             .syntax               unified

    Somewhere you want to tell the assembler, that you're about to write Cortex-M0 code, so before your Cortex-M0 code, write the following line:

                             .cpu                    cortex-m0

    ... If you at some point want to write cortex-m4 code in the same source file, just switch ...

                             .cpu                    cortex-m4

    Then you do not need to convert the code to a hex-file, you still need to start up the Cortex-M0 core from your Cortex-M4 code, but I find it a lot easier this way myself.

    Remember: You can share your Cortex-M0 code with the Cortex-M4. The Cortex-M4 can run the Cortex-M0 code, but the Cortex-M0 cannot run the Cortex-M4 code. But you should be careful. If the Cortex-M4 is running the Cortex-M0 code, then the Cortex-M4 is stalling the Cortex-M0, because they're suddenly accessing the same memory space.

    -So it's a good idea to keep the Cortex-M0 code in one Flash bank, and the Cortex-M4 code in the other Flash-bank.

    (Or: You may want to run some of the code from SRAM, if it needs to run extra fast)

    -See "Using GNU Assembler" for more information about what it can do.

Reply
  • As allenwillson already mentioned, you can build two different executables:

    1. A Cortex-M0 executable
    2. A Cortex-M4 executable

    You convert the Cortex-M0 executable to a hex-file and from your Cortex-M4 code, you load the image and start the Cortex-M0 core.

    But there is a different way, which has not been covered in any documentation I know of.

    I write all the code in assembly language; sometimes I write some files in C for the Cortex-M4, though.

    But I write the Cortex-M0 code in assembly language, and I use GCC and GAS for building my project.

    I recommend that the first line of your assembly file is...

                             .syntax               unified

    Somewhere you want to tell the assembler, that you're about to write Cortex-M0 code, so before your Cortex-M0 code, write the following line:

                             .cpu                    cortex-m0

    ... If you at some point want to write cortex-m4 code in the same source file, just switch ...

                             .cpu                    cortex-m4

    Then you do not need to convert the code to a hex-file, you still need to start up the Cortex-M0 core from your Cortex-M4 code, but I find it a lot easier this way myself.

    Remember: You can share your Cortex-M0 code with the Cortex-M4. The Cortex-M4 can run the Cortex-M0 code, but the Cortex-M0 cannot run the Cortex-M4 code. But you should be careful. If the Cortex-M4 is running the Cortex-M0 code, then the Cortex-M4 is stalling the Cortex-M0, because they're suddenly accessing the same memory space.

    -So it's a good idea to keep the Cortex-M0 code in one Flash bank, and the Cortex-M4 code in the other Flash-bank.

    (Or: You may want to run some of the code from SRAM, if it needs to run extra fast)

    -See "Using GNU Assembler" for more information about what it can do.

Children
  • Hi jensbauer

    Sorry for the latency

    How can I add M0 image(Hex file) to M4 project?

    Can you please explain how to do that in assembly?

    Thank you

  • You write a text file ending in .s (or .S), and add it to your Cortex-M4 project like you would add a .c file there.

    This file will now be built using the assembler instead of the compiler (.s files are built using the assembler, .c and .cpp files by the compiler).

    A short example file showing most of the assembler-directives you would be using:

    ;/* File: example.s */

            .syntax unified             /* this makes the assembler automatically generate IT instructions for you */

            .cpu    cortex-m0           /* this selects the cortex-m0 architecture and helps you avoid using cortex-m3/cortex-m4 instructions */

            .text                       /* this makes sure the code goes into the .text section */

            .global m0vectors

            .word   0x20004000          /* this defines the initial stack pointer for the Cortex-M0 */

            .word   m0reset             /* the reset exception vector */

    /* here you should place your other exception vectors. There are too many to include in this example */


            .global m0test              /* this exports the symbol m0test, so you can reference it from for instance C */

            .func   m0test,m0test       /* this names the symbol m0test as a function (for the debug-info) */

            .type   m0test,%function    /* this tells the assembler (and linker) what kind of symbol we're generating */

            .thumb_func                 /* this is necessary if pointers use the symbol */

            .align                      /* this makes sure the code is positioned on a 16-bit boundary */

    m0test:                             /* this defines the actual symbol */

            ldr     r0,=0x01234567      /* example code, load a value into r0 */

            bx      lr                  /* return to the calling function */


    m0reset:

            bl      m0test              /* this is the startup-code, call our function */

    lockup: wfi                         /* sleep the CPU; it'll wake up if an interrupt occurs */

             b       lockup              /* go back to sleep */


            .size   m0test, . - m0test  /* this tells the linker how big this function is, so it can correctly exclude it if it's unused */

            .endfunc                    /* this marks the end of the function (for the debug-info) */

    You can then refer to the code from your C file...

    /* File: main.c */

    #include <ipc_queue.h>

    /* Note: you don't need argc and argv on a microcontroller. */

    int main(int argc, const char *argv[])

    {

         IPC_haltSlave();

         SET_SLAVE_SHADOWREG(m0vectors);

         IPC_startSlave();

         while(1)

         {

              asm volatile("wfi");

         }

         return(0);

    }

    I'm not completely sure about the .c file; I haven't tested the code, so expect a lot of errors. It would be something in that direction, though.