上一篇已经创建了一个machine的模块并实现了函数,按照这个方式可以将引脚、串口、定时器等所有外设的功能都添加到这个模块里面。但是,这么多的外设,每个外设还有不少的操作函数,全部一起加到模块里,使用起来非常的不方便。MicroPython支持将一个class添加到模块里,因此我们可以将每个外设设计成一个单独的class,外设的操作作为class的method,这样添加到模块里,调用时就比较便捷了。本文以LED为例进行说明。
classes
跟模块类似,类也是一个c结构体,只是跟模块的字段不完全一样而已。
STATIC const mp_rom_map_elem_t led_locals_dict_table[] = {
};
STATIC MP_DEFINE_CONST_DICT(led_locals_dict, led_locals_dict_table);
const mp_obj_type_t pyb_led_type = {
{&mp_type_type},
.name = MP_QSTR_LED,
.print = led_obj_print,
.make_new = led_obj_make_new,
.locals_dict = (mp_obj_dict_t *)&led_locals_dict,
};
可以看到,一个类需要两个函数:make_new
用于构造类并分配类需要的所有内存空间,print
用于打印该类的对象。
// this is the actual C-structure for our new object
typedef struct _pyb_led_obj_t
{
// base represents some basic information, like type
mp_obj_base_t base;
// a member created by us
mp_uint_t led_id;
} pyb_led_obj_t;
STATIC const pyb_led_obj_t pyb_led_obj[] = {
{{&pyb_led_type}, PYB_LED_TOP_LEFT_1},
{{&pyb_led_type}, PYB_LED_TOP_RIGHT_1},
{{&pyb_led_type}, PYB_LED_TOP_RIGHT_2},
{{&pyb_led_type}, PYB_LED_TOP_LEFT_2},
};
首先定义一个LED的对象结构,里面包含了类的数据和一个额外的字段。然后定义了4个静态的LED对象。接下来创建print
函数用于打印这些对象:
void led_obj_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind)
{
pyb_led_obj_t *self = MP_OBJ_TO_PTR(self_in);
mp_printf(print, "LED(%u)", self->led_id);
}
还有构造函数
STATIC mp_obj_t led_obj_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args)
{
// check arguments
mp_arg_check_num(n_args, n_kw, 1, 1, false);
// get led number
mp_int_t led_id = mp_obj_get_int(args[0]);
// check led number
if (!(1 <= led_id && led_id <= NUM_LEDS))
{
nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "LED(%d) doesn't exist", led_id));
}
// return static led object
return MP_OBJ_FROM_PTR(&pyb_led_obj[led_id - 1]);
}
到这里一个类所需的基本元素就都具备了,紧接着实现类的方法。
methods
这里实现了LED的3个方法,on、off和toggle。
/// Turn the LED on.
mp_obj_t led_obj_on(mp_obj_t self_in)
{
pyb_led_obj_t *self = MP_OBJ_TO_PTR(self_in);
Board_LED_Set(self->led_id, true);
return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(led_obj_on_obj, led_obj_on);
/// \method off()
/// Turn the LED off.
mp_obj_t led_obj_off(mp_obj_t self_in)
{
pyb_led_obj_t *self = MP_OBJ_TO_PTR(self_in);
Board_LED_Set(self->led_id, false);
return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(led_obj_off_obj, led_obj_off);
/// \method toggle()
/// Toggle the LED between on and off.
mp_obj_t led_obj_toggle(mp_obj_t self_in)
{
pyb_led_obj_t *self = MP_OBJ_TO_PTR(self_in);
Board_LED_Toggle(self->led_id);
return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(led_obj_toggle_obj, led_obj_toggle);
将实现好的方法添加到类字典里,同时添加的还有一些类常量。
STATIC const mp_rom_map_elem_t led_locals_dict_table[] = {
// instance methods
{MP_ROM_QSTR(MP_QSTR_on), MP_ROM_PTR(&led_obj_on_obj)},
{MP_ROM_QSTR(MP_QSTR_off), MP_ROM_PTR(&led_obj_off_obj)},
{MP_ROM_QSTR(MP_QSTR_toggle), MP_ROM_PTR(&led_obj_toggle_obj)},
// class constants
{MP_ROM_QSTR(MP_QSTR_TOP_LEFT_1), MP_ROM_INT(PYB_LED_TOP_LEFT_1)},
{MP_ROM_QSTR(MP_QSTR_TOP_RIGHT_1), MP_ROM_INT(PYB_LED_TOP_RIGHT_1)},
{MP_ROM_QSTR(MP_QSTR_TOP_RIGHT_2), MP_ROM_INT(PYB_LED_TOP_RIGHT_2)},
{MP_ROM_QSTR(MP_QSTR_TOP_LEFT_2), MP_ROM_INT(PYB_LED_TOP_LEFT_2)},
};
将类添加到模块
上面已经完成了一个完整的类,想要能够访问,还需要将这个类添加到模块中。注意:不要忘了在qstrdefsport.h中定义所有的QSTR名字,不然编译报错!!!
STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
{MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_machine)},
{MP_ROM_QSTR(MP_QSTR_reset), MP_ROM_PTR(&machine_reset_obj)},
{MP_ROM_QSTR(MP_QSTR_freq), MP_ROM_PTR(&machine_freq_obj)},
{MP_ROM_QSTR(MP_QSTR_LED), MP_ROM_PTR(&pyb_led_type)},
};
使用已添加的method
import machine
led = machine.LED(machine.LED.TOP_LEFT_1)
led.on()
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