Convert Kinetis Project to use newlib instead of EWL

You can convert the ewl hello world project created for Kinetis devices to use newlib by making several changes to the build settings and the startup code. The purpose of these changes is to help the build process search the right directories for the right library files, and provide the right instructions to the linker.

Perform these steps to convert Kinetis project to use newlibe instead of EWL.

1. Start the IDE.
2. In the CodeWarrior Projects view, select the project for which you want to modify the build properties.
3. Select Project > Properties .

   The Properties window appears. The left side of this window has a properties list. This list shows the build properties that apply to the current project.

4. Expand the C/C++ Build property.
5. Select Settings .

   The Properties window shows the corresponding build properties.

6. Select Librarian and clear the Enable automatic library configurations checkbox.
7. Select ARM Ltd Windows GCC C Compiler > Directories .
8. Select and remove the EWL C/C++/Runtime include directories paths.

   For example remove:

   "${MCUToolsBaseDir}/ARM_GCC_Support/ewl/EWL_C/include" and

   "${MCUToolsBaseDir}/ARM_GCC_Support/ewl/EWL_Runtime/ include"

   This ensures that the compiler does not search in these EWL directories.

   Figure 1. EWL C/C++/Runtime Include Directories Paths
   
   
9. Select ARM Ltd Windows GCC C Linker > Libraries .
10. Clear the EWL library search path (-L) .

    For example, remove:

    "${MCUToolsBaseDir}/ARM_GCC_Support/ewl/lib/armv6-m"

    The linker will not be searching for the ewl library.

    Figure 2. ARM Ltd Windows GCC C Linker Libraries
    
    
11. Select ARM Ltd Windows GCC C Linker > Miscellaneous .
12. Under Linker flags (-Xlinker [option]) add:

    -lc -lm -lgcc -lrdimon

    Figure 3. ARM Ltd Windows GCC C Linker Miscellaneous Settings
    
    
13. Scroll to the bottom of the settings panel and in the Other flags text box add -specs=rdimon.specs.
    Figure 4. ARM Ltd Windows GCC C Linker Miscellaneous Settings - Other flags
    
    
14. Remove ' __arm_start.c', '__arm_end.c' and 'runtime_configuration.h' from Project_Settings/Startup_Code.
    Figure 5. Remove __arm_start.c, __arm_end.c and runtime_configuration.h - Before
    
    
    Figure 6. Remove __arm_start.c, __arm_end.c and runtime_configuration.h - After
    
    
15. Click OK to apply the modified build settings for the project.

    The above changes to the build settings ensure that the build picks newlib instead of ewl. However to make the build complete, you need to provide a startup routine.

Newlib provides a startup routine called _start. However, you must write a wrapper startup function that will do the following tasks before calling newlib '_start'.

1. Initialize the sp register.
2. Call the __init_hardware function which is defined in kinetis_sysinit.c.
3. Copy ROM section to RAM sections. This function call is not required if you are using RAM programming.
4. Call the _start function.

The following code demonstrates how what the wrapper startup file looks like. This file includes a __rom_to_ram_copy function along with wrapper startup function __thumb_startup.

To write a startup file and add it to the project, perform these steps.

1. Right click on the Sources folder of the project and select New/Source File .
2. Provide a name to the source file. For example startup.S.

   Alternatively, you can also create a *. c file and port the following code to inline c code.

3. Click Finish .
4. Open the recently created .S file and copy the code in the following listing.
5. The startup function __thumb_startup is included as an entry point in the existing linker command file. Therefore, the __thumb_startup function will be called first as execution starts.
   Listing: Inline C Code

    .syntax unified
       .arch armv6-m
   
    .text 
       .thumb
       .thumb_func
   
   .align
    2
   
   .globl
      __rom_to_ram_copy
   
    .type 
      __rom_to_ram_copy, %function
   
   __rom_to_ram_copy: 
   
   ldr r1,=___ROM_AT
   ldr r2,=_sdata
   ldr r3,=_edata
   
       subs    r3, r2
       ble    rom_to_ram_loop_end
   
   movs r4,0
   
   rom_to_ram_loop_begin: 
   
      ldr    r0, [r1,r4]
      str    r0, [r2,r4]
   
       adds   r4, 4
       cmp    r4, r3
       blt    rom_to_ram_loop_begin
   
   rom_to_ram_loop_end: 
   
   mov pc,lr
   
       .pool
   
    .size
    __rom_to_ram_copy, . - __rom_to_ram_copy
       .thumb_func
   
    .align
    2
   
    .globl 
      __thumb_startup
   
    .type
       __thumb_startup, %function
   
   __thumb_startup: 
       ldr    r0, =_estack
       mov    sp,r0
       ldr    r0, =__init_hardware
       blx    r0
       ldr    r0, =__rom_to_ram_copy
       blx    r0
       ldr    r0, =_start
       bx     r0
       .pool
   
    .size
    __thumb_startup, . - __thumb_startup
       .end