C module in micropython

[micropyt]

Hello, I have a problem with creating the mpy file of cmodule.
Is it possible to call another C function inside like this?

STATIC mp_obj_t Timers_PWM_OFF(void)
{
  turn_PWM_OFF(); 

  return mp_obj_new_bool (true);

}

[git-n-pissed]

The only experience I have adding C functions is in modsys.c so they are available in the sys module. Adding functions like that requires three changes to modsys.c

First, create the function itself. I'm not sure how picky MicroPython is about the name of the function, but mine have always followed this naming format with the "my_function_name" being what you would change:

STATIC mp_obj_t mp_micropython_my_funcion_name(void) {
    return mp_obj_new_bool(true);  // Whatever you need to return
}

Second, define a constant function object. I do this right below the function that was just created:

STATIC MP_DEFINE_CONST_FUN_OBJ_0(mp_micropython_my_function_name_obj, mp_micropython_my_function_name);

Third, the function needs to be mapped in mp_module_sys_globals_table:

STATIC const mp_rom_map_elem_t mp_module_sys_globals_table[] = {
    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_sys) },  //  I believe this line needs to be first in the map.  Put your function mappings below it.
    { MP_ROM_QSTR( MP_QSTR_my_function_name), MP_ROM_PTR(&mp_micropython_my_function_name_obj) },
    ...

The process for adding C functions to other modules (i.e. not sys) should be similar.

[jimmo]

Is it possible to call another C function inside like this?

@micropyt You might need to provide more context. In particular, what do you mean by "creating the mpy file of cmodule" -- is this https://docs.micropython.org/en/latest/develop/natmod.html ?

Yes you can call any C function, but it will need to be statically linked into your module.

[dlech]

How can I write makefile to search for all header files?

You can use CFLAGS_MOD=... to add any addition compiler flags like -I for additional header file locations. (There is also CXXFLAGS_MOD and LDFLAGS_MOD for C++ flags and linker flags.)

[stinos]

Wait wasn't CFLAGS_MOD largely or even completely removed? See d6d8722.

[dlech]

Thanks, I must have been looking at an older version.

[jimmo]

Yes, they are now replaced with

CFLAGS_USERMOD, CXXFLAGS_USERMOD, LDFLAGS_USERMOD

[jimmo]

What do you mean by statically linked? Do you mean linked by header file?

@micropyt The dynamic native module must not have any dependencies -- i.e. any code that it depends on must be statically linked into it. This is unrelated to header files.