Extend Circuitpython with C modules

Question

I'm trying to follow this article but it's very outdated https://learn.adafruit.com/extending-circuitpython/inside-the-virtual-machine

The last part of how to hook the example mymodule. The files content and structure is very different. Does anyone know how to hook it? I don't know where to place the references and how.

Milliways · Accepted Answer · 2023-12-28T00:45:27.977

CircuitPython is a weird Adafruit invention so I can't comment on their code, but if you want to include c code I suggest you explore Ctypes in normal python to learn the ropes.

There are a few different ways of calling c from python but I use Ctypes in my code (which is what Adafruit appear to use).

It took me a while to get my head around calling c from python and I have used other methods but found this the simplest (at least for simple code). I use this to call my shared GPIO library from python.

I have included a simple example I used to test lists.
The link in the c code has other examples.

#! /usr/bin/env python3
# import os
# import subprocess
# 2022-12-08
List test
import ctypes
clibrary = ctypes.CDLL('/home/ian/PyTest/ctype1/clibrary.so')
L = ['A', 'B', 'C']
lB = [97, 98, 99]
BA = bytes(lB)
print(BA)
B2 = bytes([97, 98, 0, 99])
pr_list = clibrary.pr_list
pr_list.argtypes = [ctypes.c_char_p, ctypes.c_int]
pr_list(BA, len(BA))
pr_list(B2, len(B2))
case_list = clibrary.case_list
case_list.argtypes = [ctypes.c_char_p, ctypes.c_int]
BC = bytes([0]*len(BA))
print("BA = ", BA)
print("B2 = ", B2)
print("BC = ", BC)
copy_list = clibrary.copy_list
copy_list.argtypes = [ctypes.c_char_p, ctypes.c_char_p, ctypes.c_int]
copy_list(BA, BC, len(BA))
print("BC = ", BC)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

// https://coderslegacy.com/python/ctypes-tutorial/
// gcc -fPIC -shared -o clibrary.so clibrary.c

void prompt(int num) { printf("The number %d was entered", num); }

int add(int num1, int num2) { return num1 + num2; }

void display(char *str) { printf("%s", str); }

void increment(char *str) {
  for (int i = 0; str[i] != 0; i++) {
    str[i] = str[i] + 1;
  }
}

char *alloc_memory(void) {
  char *str = strdup("Hello World");
  printf("Memory allocated...\n");
  return str;
}

void free_memory(char *ptr) {
  printf("Freeing memory...\n");
  free(ptr);
}

//  ______________
struct Point {
  int x;
  int y;
};

void printPoint(struct Point p) { printf("%d %d\n", p.x, p.y); }

struct Point getPoint() {
  struct Point temp;
  temp.x = 50;
  temp.y = 100;
  return temp;
}

//  ______________

void floatest(float num) {
  printf("The number %f was entered\n", num);
  printf("The number %x was entered\n", num);
}

//  ______________

char *GetStr(void)
//  { return "TestString"; }
//  { return "{'A':13, 'B':14, 'C':'pi'}"; }
{
  return "{'p1_revision':3, 'type':'Pi 3 Model B+', 'ram':'1G', "
         "'processor':'BCM2837', 'manufacturer':'Sony', 'revision':'a020d3'}";
}

// 2022-12-04
void pr_pointer(char *str) { printf("%s", str); }

// 2022-12-07
void pr_list(const unsigned char *lst, unsigned count) {
  printf("%s %d\n", lst, count);
  for (int i = 0; i < count; i++) {
    printf("%d ", lst[i]);
  }
  printf("\n");
}

// 2022-12-07
void case_list(unsigned char *lst, unsigned count) {
  printf("%s %d\n", lst, count);
  for (int i = 0; i < count; i++) {
    lst[i] = toupper(lst[i]);
    printf("%d ", lst[i]);
  }
  printf("\n");
}

void copy_list(unsigned char *lst1,  char *lst2, unsigned count) {
  for (int i = 0; i < count; i++) {
    lst2[i] = toupper(lst1[i]);
  }
}

Extend Circuitpython with C modules

1 Answers1

List test