移植 MicroPython

MicroPython项目支持多个不同的MCU或平台，他们在 MicroPython的port 目录里面。当我们的项目能够在port 目录里面找到支持的单片机时，我们可以直接应用port 目录里面的工程，但是当port 目录里面没有支持我们的单片机时，就需要我们自己移植MicroPython到相应的的单片机上。
通常来说，向单片机移植MicroPython时需要的工作有：
1、设置工具链（配置 Makefile 等）
2、初始化CPU和编写bootloader
3、初始化一切开发和调试所需的基本驱动程序（例如 GPIO、UART）。
4、编写特定的配置
5、实现单片机的modules。
下面以一个最小的MicroPython 固件为演示案例：
在port 目录下创建一个example_port文件夹，该文件夹就是放置工程文件的地方。该文件夹最少要包含5个文件，分别为main.c、 Makefile、mpconfigport.h、 mphalport.c、 mphalport.h。结构如下：

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

其中main.c文件是工程的主文件，Makefile是编译文件，mpconfigport.h文件的作用是MicroPython 配置文件，mphalport.c是单片机特有的一些其他配置，mphalport.c文件的作用是实现标准输入/输出。

一、各文件代码内容

1.1、main.c文件

#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文件

# 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文件

#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文件

static inline void mp_hal_set_interrupt_char(char c) {}

1.5、mphalport.c文件

#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

要添加一个自定义module名字为myport，首先在文件夹中添加module定义的文件名字为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);

编写完modmyport.c文件后，还需要再次编辑 Makefile ，作用是添加modmyport.c到SRC_C列表中。如下所示：

SRC_C = \main.c \modmyport.c \mphalport.c \...SRC_QSTR += modport.c