Execute Python code from C

General discussions and questions abound development of code with MicroPython that is not hardware specific.
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stegomon
Posts: 1
Joined: Sun May 13, 2018 2:34 pm

Execute Python code from C

Post by stegomon » Sun May 13, 2018 2:49 pm

I'm working on a way to execute Python code from a FreeRTOS callback handler. The way I tried to do this is by using the parse_compile_execute function from "lib/utils/pyexec.c" and feeding it a qstr with content like "print(123)".

This does work when the function is called from the main thread in the file "main.c". However, my program gets locked up with a "LoadProhibited" error when I'm calling this function from another source, in my case from a Bluetooth callback handler. Specifically, it panics when executing mp_globals_get() in "runtime.h":130.

Does anyone know why it is not working as if it were called from the "main.c" file? Is there a workaround?

Thanks in advance,

stegomon

jickster
Posts: 284
Joined: Thu Sep 07, 2017 8:57 pm

Re: Execute Python code from C

Post by jickster » Tue May 15, 2018 10:59 pm

stegomon wrote:
Sun May 13, 2018 2:49 pm
I'm working on a way to execute Python code from a FreeRTOS callback handler. The way I tried to do this is by using the parse_compile_execute function from "lib/utils/pyexec.c" and feeding it a qstr with content like "print(123)".

This does work when the function is called from the main thread in the file "main.c". However, my program gets locked up with a "LoadProhibited" error when I'm calling this function from another source, in my case from a Bluetooth callback handler. Specifically, it panics when executing mp_globals_get() in "runtime.h":130.

Does anyone know why it is not working as if it were called from the "main.c" file? Is there a workaround?

Thanks in advance,

stegomon
To compile and execute code, you need to call these functions.

You need to populate first 3 vars with your own values.

Code: Select all

const char* ptr_code;
unsigned int code_length;
bool repl;

bool ret_val = false;

mp_parse_input_kind_t parse_type = MP_PARSE_SINGLE_INPUT;
if (repl == true)
{
	parse_type = MP_PARSE_SINGLE_INPUT;
}
else
{
	parse_type = MP_PARSE_FILE_INPUT;
}

mp_lexer_t * lex = mp_lexer_new_from_str_len(0, ptr_code, (size_t)code_length, (size_t)0);
mp_parse_tree_t parse_tree = mp_parse(lex, parse_type);
mp_obj_t module_func = mp_compile(&parse_tree, lex->source_name, MP_EMIT_OPT_NONE, repl);
mp_call_function_0(module_func);
Try that and reply with what happens.

stijn
Posts: 257
Joined: Thu Apr 24, 2014 9:13 am

Re: Execute Python code from C

Post by stijn » Wed May 16, 2018 8:22 am

jickster wrote:
Tue May 15, 2018 10:59 pm
To compile and execute code, you need to call these functions.
mp_parse_compile_execute already does that for the OP so it's unlikely the problem is there.
Rather has something to do with doing this from within a callback.

I don't know anything about FreeRTOS nor how it's threads/callbacks are implemented in MicroPython but if that callback actually runs on a seperate thread or as an interrupt without MicroPython knowing about it, hence without synchronization, there's a data race which needs to be resolved. Possible solutions include: using synchronisation, if available, and/or doing something like setting a flag in the callback and polling that from a loop in the same thread which initialized MicroPython.

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