keyboard.c

通过调节一个可变电阻得到变化的电压来模拟一个湿度度传感器

#include <reg51.h>

#define CHECK_KEY_DOWN 	0
#define CHECK_KEY_UP   	1
#define KEY_UP			0
#define KEY_DOWN		1

sbit _p33 = P3^3;
sbit _p34 = P3^4;
sbit _p35 = P3^5;
sbit _p36 = P3^6;

char _key_status = CHECK_KEY_DOWN;
char _key_idx = 0;
char _key_led = 0;

void _delay_1ns() {
}

void _p34_plus() {
    _p34 = 0;
    _delay_1ns();
    _p34 = 1;
    _delay_1ns();
    _p34 = 0;
}

void _p35_plus() {
    _p35 = 0;
    _delay_1ns();
    _p35 = 1;
    _delay_1ns();
    _p35 = 0;
}

void serial_output(unsigned char out) {
    char i = 0;
    for (i = 7; i >= 0 ; i--) {
        _p33 = (out >> i)& 0x01;
        _p34_plus();
    }
    _p35_plus();
}

char _check_key(unsigned char _key_idx) {
	serial_output(_key_led | (~(0x01<<_key_idx)) & 0x0f );
	if (_p36 == 0) {
		return KEY_DOWN;
	} else {
		return KEY_UP;
	}
}

char get_key(void) {
	char result = -1;
	if (_key_status == CHECK_KEY_DOWN) {
		if (_check_key(_key_idx) == KEY_DOWN) {
			_key_status = CHECK_KEY_UP;
		} else {
			_key_status = CHECK_KEY_DOWN;
			if (++_key_idx == 4) {
				_key_idx = 0;
			}
		}
	} else if (_key_status == CHECK_KEY_UP) {
		if (_check_key(_key_idx) == KEY_UP) {
			result = _key_idx;
			_key_status = CHECK_KEY_DOWN;
			if (++_key_idx == 4) {
				_key_idx = 0;
			}
		} else {
			_key_status = CHECK_KEY_UP;
		}
	}
	return result;
}