Compiling baremetal C program for Arm Cortex-M0+

arm-cortexm0plus-compilation.md

Compiling baremetal C program for Arm Cortex-M0+

1. Install Arm GNU GCC compiler. Download the tar.xv archive from: https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads Define the environmet variable $ARM_GCC_ROOT to point to the location where you extract this archive. This guide was tested with arm-gnu-toolchain-11.3.rel1-x86_64-arm-none-eabi

2. Update your $PATH and $LD_LIBRARY_PATH as follows:

   setenv PATH $ARM_GCC_ROOT/bin:$PATH
   setenv LD_LIBRARY_PATH $ARM_GCC_ROOT/lib:$LD_LIBRARY_PATH
   

3. Clone Arm CMSIS 5 as follows:

   git clone https://github.com/ARM-software/CMSIS_5
   cd CMSIS_5
   setenv CMSIS_ROOT `pwd`
   

4. Create a makefile named Makefile with the following content:

   SYSROOT    = $(ARM_GCC_ROOT)/arm-none-eabi
   TEST      ?= hello
   # See: https://interrupt.memfault.com/blog/arm-semihosting
   ARM_FLAGS  = --specs=rdimon.specs -mcpu=cortex-m0plus
   CC         = arm-none-eabi-gcc --sysroot=$(SYSROOT) $(ARM_FLAGS)
   CFLAGS     = -std=c99 -O2
   CPPFLAGS   = -I$(CMSIS_ROOT)/Device/ARM/ARMCM0plus/Include
   CPPFLAGS  += -I$(CMSIS_ROOT)/CMSIS/Core/Include
   CPPFLAGS  += -DARMCM0P
   LDFLAGS    = -T$(CMSIS_ROOT)/Device/ARM/ARMCM0plus/Source/GCC/gcc_arm.ld
   SRCS       = hello.c
   SRCS      += $(wildcard $(CMSIS_ROOT)/Device/ARM/ARMCM0plus/Source/*.c)
   BINS       = $(TEST).elf
   .PHONY: all clean
   all: $(BINS)
   $(TEST).elf: $(SRCS)
       $(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS) $^ -o $@
   
   clean:
       $(RM) $(BINS)
   

5. Create a test program called hello.c as follows:

    #include <stdio.h>
    #include <stdint.h>
   
    #include <ARMCM0plus.h>
   
    uint32_t volatile msTicks = 0;
   
    void SysTick_Handler (void) { }
   
    void WaitForInterrupt (void)  {
      uint32_t curTicks;
   
      curTicks = msTicks;
      while (msTicks == curTicks) {
        __WFI();
      }
    }
   
    void Device_Initialization (void) {
      SystemInit();
      SysTick_Config (SystemCoreClock / 1000);
      NVIC_SetPriority (1, 1);
      NVIC_EnableIRQ (1);
    }
   
   
    int main (void) {
      int sum = 0, i = 0;
      Device_Initialization ();
      printf("Hello World!\n");
      for (i = 0; i < 10; i++)  {
        WaitForInterrupt();
        printf("Interrupt received!\n");
      }
      for (int i = 0; i < 1000; i++) {
        sum += i + (i & 1);
      }
      printf("sum = %d\n", sum);
      return 0;
    }
   

6. Compile as follows:

    make clean all