移植 MicroPython

??MicroPython專案支持多個不同的MCU或平臺，他們在 MicroPython的port 目錄里面，當我們的專案能夠在port 目錄里面找到支持的單片機時，我們可以直接應用port 目錄里面的工程，但是當port 目錄里面沒有支持我們的單片機時，就需要我們自己移植MicroPython到相應的的單片機上，
??通常來說，向單片機移植MicroPython時需要的作業有：
??1、設定工具鏈（配置 Makefile 等）
??2、初始化CPU和撰寫bootloader
??3、初始化一切開發和除錯所需的基本驅動程式（例如 GPIO、UART），
??4、撰寫特定的配置
??5、實作單片機的modules，
??下面以一個最小的MicroPython 韌體為演示案例：
??在port 目錄下創建一個example_port檔案夾，該檔案夾就是放置工程檔案的地方，該檔案夾最少要包含5個檔案，分別為main.c、 Makefile、mpconfigport.h、 mphalport.c、 mphalport.h，結構如下：

ports/example_port/
├── main.c
├── Makefile
├── mpconfigport.h
├── mphalport.c
└── mphalport.h

??其中main.c檔案是工程的主檔案，Makefile是編譯檔案，mpconfigport.h檔案的作用是MicroPython 組態檔，mphalport.c是單片機特有的一些其他配置，mphalport.c檔案的作用是實作標準輸入/輸出，

一、各檔案代碼內容

1.1、main.c檔案

#include "py/compile.h"
#include "py/gc.h"
#include "py/mperrno.h"
#include "py/stackctrl.h"
#include "lib/utils/gchelper.h"
#include "lib/utils/pyexec.h"

// Allocate memory for the MicroPython GC heap.
static char heap[4096];

int main(int argc, char **argv) {
    // Initialise the MicroPython runtime.
    mp_stack_ctrl_init();
    gc_init(heap, heap + sizeof(heap));
    mp_init();
    mp_obj_list_init(MP_OBJ_TO_PTR(mp_sys_path), 0);
    mp_obj_list_init(MP_OBJ_TO_PTR(mp_sys_argv), 0);

    // Start a normal REPL; will exit when ctrl-D is entered on a blank line.
    pyexec_friendly_repl();

    // Deinitialise the runtime.
    gc_sweep_all();
    mp_deinit();
    return 0;
}

// Handle uncaught exceptions (should never be reached in a correct C implementation).
void nlr_jump_fail(void *val) {
    for (;;) {
    }
}

// Do a garbage collection cycle.
void gc_collect(void) {
    gc_collect_start();
    gc_helper_collect_regs_and_stack();
    gc_collect_end();
}

// There is no filesystem so stat'ing returns nothing.
mp_import_stat_t mp_import_stat(const char *path) {
    return MP_IMPORT_STAT_NO_EXIST;
}

// There is no filesystem so opening a file raises an exception.
mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
    mp_raise_OSError(MP_ENOENT);
}

1.2、Makefile檔案

# Include the core environment definitions; this will set $(TOP).
include ../../py/mkenv.mk

# Include py core make definitions.
include $(TOP)/py/py.mk

# Set CFLAGS and libraries.
CFLAGS = -I. -I$(BUILD) -I$(TOP)
LIBS = -lm

# Define the required source files.
SRC_C = \
    main.c \
    mphalport.c \
    lib/mp-readline/readline.c \
    lib/utils/gchelper_generic.c \
    lib/utils/pyexec.c \
    lib/utils/stdout_helpers.c \

# Define the required object files.
OBJ = $(PY_CORE_O) $(addprefix $(BUILD)/, $(SRC_C:.c=.o))

# Define the top-level target, the main firmware.
all: $(BUILD)/firmware.elf

# Define how to build the firmware.
$(BUILD)/firmware.elf: $(OBJ)
    $(ECHO) "LINK $@"
    $(Q)$(CC) $(LDFLAGS) -o $@ $^ $(LIBS)
    $(Q)$(SIZE) $@

# Include remaining core make rules.
include $(TOP)/py/mkrules.mk

1.3、mpconfigport.h檔案

#include <stdint.h>

// Python internal features.
#define MICROPY_ENABLE_GC                       (1)
#define MICROPY_HELPER_REPL                     (1)
#define MICROPY_ERROR_REPORTING                 (MICROPY_ERROR_REPORTING_TERSE)
#define MICROPY_FLOAT_IMPL                      (MICROPY_FLOAT_IMPL_FLOAT)

// Fine control over Python builtins, classes, modules, etc.
#define MICROPY_PY_ASYNC_AWAIT                  (0)
#define MICROPY_PY_BUILTINS_SET                 (0)
#define MICROPY_PY_ATTRTUPLE                    (0)
#define MICROPY_PY_COLLECTIONS                  (0)
#define MICROPY_PY_MATH                         (0)
#define MICROPY_PY_IO                           (0)
#define MICROPY_PY_STRUCT                       (0)

// Type definitions for the specific machine.

typedef intptr_t mp_int_t; // must be pointer size
typedef uintptr_t mp_uint_t; // must be pointer size
typedef long mp_off_t;

// We need to provide a declaration/definition of alloca().
#include <alloca.h>

// Define the port's name and hardware.
#define MICROPY_HW_BOARD_NAME "example-board"
#define MICROPY_HW_MCU_NAME   "unknown-cpu"

#define MP_STATE_PORT MP_STATE_VM

#define MICROPY_PORT_ROOT_POINTERS \
    const char *readline_hist[8];

1.4、mphalport.h檔案

static inline void mp_hal_set_interrupt_char(char c) {}

1.5、mphalport.c檔案

#include <unistd.h>
#include "py/mpconfig.h"

// Receive single character, blocking until one is available.
int mp_hal_stdin_rx_chr(void) {
    unsigned char c = 0;
    int r = read(STDIN_FILENO, &c, 1);
    (void)r;
    return c;
}

// Send the string of given length.
void mp_hal_stdout_tx_strn(const char *str, mp_uint_t len) {
    int r = write(STDOUT_FILENO, str, len);
    (void)r;
}

二、添加module

??要添加一個自定義module名字為myport，首先在檔案夾中添加module定義的檔案名字為modmyport.c

#include "py/runtime.h"

STATIC mp_obj_t myport_info(void) {
    mp_printf(&mp_plat_print, "info about my port\n");
    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_0(myport_info_obj, myport_info);

STATIC const mp_rom_map_elem_t myport_module_globals_table[] = {
    { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_myport) },
    { MP_ROM_QSTR(MP_QSTR_info), MP_ROM_PTR(&myport_info_obj) },
};
STATIC MP_DEFINE_CONST_DICT(myport_module_globals, myport_module_globals_table);

const mp_obj_module_t myport_module = {
    .base = { &mp_type_module },
    .globals = (mp_obj_dict_t *)&myport_module_globals,
};

MP_REGISTER_MODULE(MP_QSTR_myport, myport_module, 1);

??撰寫完modmyport.c檔案后，還需要再次編輯 Makefile ，作用是添加modmyport.c到SRC_C串列中，如下所示：

SRC_C = \
    main.c \
    modmyport.c \
    mphalport.c \
    ...

SRC_QSTR += modport.c