interface to handle callback from C code

[ajie_dirgantara]

I've understand about creating an interface in C to be called from python. What I need now is how if I wanted to set callback from python, and then call those callback is from C. or maybe create some kind like software interrupt from C. how can I achieve this?

[dhylands]

The c_sample code mentioned in this thread: viewtopic.php?f=16&t=2861&p=19206#p19206 shows calling C code from python and having the C code call a callback written in python.

In particular, this line: https://github.com/dhylands/micropython ... c46acdfR24

[ajie_dirgantara]

The c_sample code mentioned in this thread: viewtopic.php?f=16&t=2861&p=19206#p19206 shows calling C code from python and having the C code call a callback written in python.

In particular, this line: https://github.com/dhylands/micropython ... c46acdfR24

Ok, is it safe to do this?

Code: Select all

mp_obj_t cb1_obj;
mp_obj_t cb2_obj;

STATIC mp_obj_t c_sample_set_callback1(mp_obj_t callback_obj) {
    cb1_obj = callback_obj;
    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(c_sample_set_callback1_obj, c_sample_set_callback1);

STATIC mp_obj_t c_sample_set_callback2(mp_obj_t callback_obj) {
    cb2_obj = callback_obj;
    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(c_sample_set_callback2_obj, c_sample_set_callback2);

then in an ISR to do :

Code: Select all

extern mp_obj_t cb1_obj;
extern mp_obj_t cb2_obj;

mp_call_function_0(cb1_obj);
mp_call_function_0(cb2_obj);

[dhylands]

That looks reasonable. Note, that when calling code from within an ISR you should wrap the call in a try/except. In C code this would look something like this:
https://github.com/micropython/micropyt ... 1376-L1396
That also disables memory allocations (since ISRs aren't allowed to perform memory allocations).

The nlr_push returns 0 if the code runs with no exception and returns non-zero if an exception was raised.

[ajie_dirgantara]

That looks reasonable. Note, that when calling code from within an ISR you should wrap the call in a try/except. In C code this would look something like this:
https://github.com/micropython/micropyt ... 1376-L1396
That also disables memory allocations (since ISRs aren't allowed to perform memory allocations).

The nlr_push returns 0 if the code runs with no exception and returns non-zero if an exception was raised.

I've try your sample code, but it fails to run the callback (no exception is raised but it just reset and back to repl), do you think below mp_obj_t should be initialized into callback object before called?

Code: Select all

mp_obj_t cb1_obj;
mp_obj_t cb2_obj;

and what is MP_STATE_PORT() macros do? in the very first example of yours, how can I create two different callbacks?

[dhylands]

I've try your sample code, but it fails to run the callback (no exception is raised but it just reset and back to repl), do you think below mp_obj_t should be initialized into callback object before called?

Code: Select all

mp_obj_t cb1_obj;
mp_obj_t cb2_obj;

Yes. If you don't call set_callback and then try to call call_callback you'll get a crash. You should probably initialize them to the none object (mp_obj_t)&mp_const_none_obj; and then you can test if they're set before trying to call them.