Compiling a native C module on ESP-WROOM-32

[IcedRooibos]

I'm trying to get started with compiling a native module on ESP32, I am using the ESP-WROOM-32 (DO1T ESP32 DEVKIT V1).

I have my architecture in the Makefile set to xtensawin and it compiles fine but when I load it onto the device and try and import it, I get an error ValueError: incompatible .mpy file

For now I'm just using the factorial.c code from https://docs.micropython.org/en/kookaberry/develop/natmod.html without any changes.

I've previously built micropython from source using the same setup and tested it and it works fine so I am thinking I have misconfigured something in the Makefile for the factorial module. Any thoughts on where I might have gone wrong?

In case there is any information I should be including here that I haven't please do let me know, I will add it in.

For the sake of completeness:

Makefile

# Location of top-level MicroPython directory
MPY_DIR = /home/IcedRooibos/micropython

# Name of module
MOD = factorial

# Source files (.c or .py)
SRC = factorial.c

# Architecture to build for (x86, x64, armv6m, armv7m, xtensa, xtensawin)
ARCH = xtensawin

# Include to get the rules for compiling and linking the module
include $(MPY_DIR)/py/dynruntime.mk

factorial.c

// Include the header file to get access to the MicroPython API
#include "py/dynruntime.h"

// Helper function to compute factorial
STATIC mp_int_t factorial_helper(mp_int_t x) {
    if (x == 0) {
        return 1;
    }
    return x * factorial_helper(x - 1);
}

// This is the function which will be called from Python, as factorial(x)
STATIC mp_obj_t factorial(mp_obj_t x_obj) {
    // Extract the integer from the MicroPython input object
    mp_int_t x = mp_obj_get_int(x_obj);
    // Calculate the factorial
    mp_int_t result = factorial_helper(x);
    // Convert the result to a MicroPython integer object and return it
    return mp_obj_new_int(result);
}
// Define a Python reference to the function above
STATIC MP_DEFINE_CONST_FUN_OBJ_1(factorial_obj, factorial);

// This is the entry point and is called when the module is imported
mp_obj_t mpy_init(mp_obj_fun_bc_t *self, size_t n_args, size_t n_kw, mp_obj_t *args) {
    // This must be first, it sets up the globals dict and other things
    MP_DYNRUNTIME_INIT_ENTRY

    // Make the function available in the module's namespace
    mp_store_global(MP_QSTR_factorial, MP_OBJ_FROM_PTR(&factorial_obj));

    // This must be last, it restores the globals dict
    MP_DYNRUNTIME_INIT_EXIT
}

[IcedRooibos]

I was initially uploading the file in factorial/factorial.mpy but instead maybe I should have uploaded the file in factorial/build/factorial.native.mpy. I renamed it to factorial.mpy before uploading (optional but just makes more sense to do it).

Now I can import factorial but I can't run factorial.factorial

>>> import factorial
>>> factorial.factorial(10)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'factorial'

Seems somewhere the name factorial hasn't registered correctly?

>>> dir(factorial)
['__class__', '__name__']
>>> factorial.__class__
<class 'module'>

I then also tried building micropython/examples/natmod/features0 https://github.com/micropython/micropython/tree/master/examples/natmod/features0 without any changes except architecture and similar issue

>>> features0.factorial(10)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'factorial'

Out of curiosity does anyone know what is the .mpy file in factorial/factorial.mpy and how is it different to factorial.native.mpy?

Edit: Quite weird, coming back to this now it seems to work. Not sure what to suggest except perhaps a restart after installing the idf and remember to source ./export.sh

[dpgeorge]

Out of curiosity does anyone know what is the .mpy file in factorial/factorial.mpy and how is it different to factorial.native.mpy?

They are both the same if you don't have any .py files that are merged into the native .mpy file. If you do have .py files (see the examples/natmod/features2 example) then the factorial/factorial.mpy file is the one that has all code merged together.

You should always use the factorial/factorial.mpy file (or whatever it's called for your module).

[damiencorpataux]

I had the exact same problem here and found a solution.

My mistake: I compiled the native C module factorial.mpy using micropython 1.20.0 (and esp-idf 5.0.2), but I was running it on an ESP-WROOM-32 with micropython 1.19.x.

Solution: I flashed micropython 1.20.0 on the ESP-WROOM-32 and it works.

Details:

Using micropython 1.20.0:

$ git --git-dir toolchain/micropython/.git log -1

commit 294baf52b346e400e2255c6c1e82af5b978b18f7 (HEAD -> master, tag: v1.20.0)
Author: Damien George <damien@micropython.org>
Date:   Wed Apr 26 15:42:28 2023 +1000

    all: Bump version to 1.20.0.

Using esp-idf 5.0.2:

$ git --git-dir toolchain/esp-idf/.git log -1

commit 5181de8ac5ec5e18f04f634da8ce173b7ef5ab73 (HEAD, tag: v5.0.2)
Author: Ivan Grokhotkov <ivan@espressif.com>
Date:   Wed May 10 09:59:18 2023 +0200

    versions: Update version to 5.0.2

Compiling native C module:

$ make -B

GEN build/factorial.config.h
CC factorial/factorial.c
LINK build/factorial/factorial.o
arch:         EM_XTENSA
text size:    101
rodata size:  8
bss size:     0
GOT entries:  3
GEN factorial.mpy

Executing on ESP-WROOM-32:

$ mpytool -p /dev/ttyUSB0 put factorial.mpy && mpytool -p /dev/ttyUSB0 repl

Entering REPL mode, to exit press CTRL + ]

$ mpytool -p /dev/ttyUSB0 put factorial.mpy && mpytool -p /dev/ttyUSB0 repl
Entering REPL mode, to exit press CTRL + ]

>>> import factorial
>>> factorial.factorial(4)
24
>>> 

HTH

[jonnor]

Mismatched versions of MicroPython for the firmware and what the module is build against by far the most likely cause of this.