1、能够理解清楚单片机IO口的结构。

2)t1相当于PnP三级管，t2相当于npn三极管

3） 强推挽io具有较强的驱动能力，电流输出能力很强。

2、能够看懂上下拉电阻的电路应用，并且熟练使用上下拉电阻。

3、理解28BYJ-48减速步进电机的工作原理。

4、能够熟练编写步进电机正反转任意角度的程序。

#include <REGX52.H>
sbit MC0 = P1^0;
sbit MC1 = P1^1;
sbit MC2 = P1^2;
sbit MC3 = P1^3;
sbit MC4 = P1^4;

sbit KeyIn1 = P2^4;
sbit KeyIn2 = P2^5;
sbit KeyIn3 = P2^6;
sbit KeyIn4 = P2^7;

sbit KeyOut1 = P2^3;
sbit KeyOut2 = P2^2;
sbit KeyOut3 = P2^1;
sbit KeyOut4 = P2^0;

static unsigned long a;
unsigned char KeySta[4][4] = { 
    {1, 1, 1, 1},  {1, 1, 1, 1},  {1, 1, 1, 1},  {1, 1, 1, 1}
};
unsigned char code KeyCodeMap[4][4] = { 
    { 0x31, 0x32, 0x33, 0x26 }, 
    { 0x34, 0x35, 0x36, 0x25 }, 
    { 0x37, 0x38, 0x39, 0x28 }, 
    { 0x30, 0x1B, 0x0D, 0x27 }  
};
void KeyDriver();
void main()
{
	  EA = 1;       
    TMOD = 0x01;  
    TH0  = 0xFC;  
    TL0  = 0x67;
    ET0  = 1;     
    TR0  = 1;     
   	while(1)KeyDriver();
}
void StartMotor(signed long angle)
{
	EA = 0;
  a = angle*4076/360;
	EA = 1;
}
void StopMotor()
{
    EA = 0;
    a = 0;
    EA = 1;

}
void KeyAction(unsigned char keycode)
{
  bit arr;
	if(keycode >= 0x30 && keycode <= 0x39)
	{
		if(arr == 0)	
		   StartMotor(360*(int)(keycode-0x30));
		else
		   StartMotor(-360*(int)(keycode-0x30));
	}
		else if(keycode == 0x26)
		{
		arr = 0;
		}
		else if(keycode == 0x28)
		{
		arr = 1;
		}
		else if (keycode == 0x25) 
    {
        StartMotor(90);
    }
    else if (keycode == 0x27)  
    {
        StartMotor(-90);
    }
    else if (keycode == 0x1B) 
    {
        StopMotor();
    }
	}
void KeyDriver()
{
    unsigned char i, j;
    static unsigned char backup[4][4] = {  
        {1, 1, 1, 1},  {1, 1, 1, 1},  {1, 1, 1, 1},  {1, 1, 1, 1}
    };
    
    for (i=0; i<4; i++)  
    {
        for (j=0; j<4; j++)
        {
            if (backup[i][j] != KeySta[i][j])  
            {
                if (backup[i][j] != 0)           
                {
                    KeyAction(KeyCodeMap[i][j]); 
                }
                backup[i][j] = KeySta[i][j];     
            }
        }
    }
}
	void KeyScan()
{
  static	unsigned char add = 0;
	 unsigned char j ;
  static unsigned char keybuf[4][4] = {  
        {0xFF, 0xFF, 0xFF, 0xFF},  {0xFF, 0xFF, 0xFF, 0xFF},
        {0xFF, 0xFF, 0xFF, 0xFF},  {0xFF, 0xFF, 0xFF, 0xFF}
    };
	    keybuf[add][0] = (keybuf[add][0] << 1) | KeyIn1;
			keybuf[add][1] = (keybuf[add][1] << 1) | KeyIn2;
			keybuf[add][2] = (keybuf[add][2] << 1) | KeyIn3;
			keybuf[add][3] = (keybuf[add][3] << 1) | KeyIn4;
		for(j = 0;j <4;j++)
		{
		if( (keybuf[add][j] & 0x0F) == 0x00 )
		{
		  KeySta[add][j] = 0;
		}
		else if((keybuf[add][j] & 0x0F) == 0x0f)
		{
			KeySta[add][j] = 1;
		}
		}
    add++;
		add = add & 0x03;
		switch(add)
		{
			case 0:KeyOut4 = 1;KeyOut1 = 0;break;
			case 1:KeyOut1 = 1;KeyOut2 = 0;break;
			case 2:KeyOut2 = 1;KeyOut3 = 0;break;
			case 3:KeyOut3 = 1;KeyOut4 = 0;break;
			default:break;
		}
}

void TurnMotor()
{
	    static unsigned char index = 0;  
    static unsigned char tmp = 0;  
	unsigned char code BeatCode[8] = {  
        0xE, 0xC, 0xD, 0x9, 0xB, 0x3, 0x7, 0x6
    };
	if(a != 0)
	{
	if(a > 0)
	{
	index++;
	index =  index & 0x07;
		a--;	
	}
	else
	{
	index--;
	index =  index & 0x07;
		a++;	
	}
	tmp = P1;
	tmp =  tmp & 0xF0;
	tmp = tmp | BeatCode[index];
	P1  = tmp;
	}
	else 
    {
        P1 = P1 | 0x0F;
    }
}
void InterruptTimer0() interrupt 1
{
   bit biv = 0;
    TH0 = 0xFC;  
    TL0 = 0x67;   
    KeyScan();  
	 biv = ~biv;
  if (biv == 1)
    {
        TurnMotor();
    }
}

5、学会蜂鸣器发声的方法。

#include <REGX52.H>
sbit BUZZ = P1^6;
void openbuzz(unsigned char arr);
void stopbuzz();
unsigned int TORH;
unsigned int TORL;
void main()
{
	unsigned int i;
	EA = 1;
	TMOD = 0x01;
	while(1)
	{
	openbuzz(4000);
	for(i = 0;i <= 40000;i++);
	stopbuzz();
	for(i = 0;i <= 20000;i++);
	openbuzz(1000);
	for(i = 0;i <= 40000;i++);
	stopbuzz();
	for(i = 0;i <= 20000;i++);
	}
}
void openbuzz(unsigned char arr)
{
	unsigned int reload;
	reload = (65536)- (11059200/12)/(arr*2);
	TORH = (unsigned int)(reload >> 8);
	TORL = (unsigned int)reload;
	TH0  = 0xFF;  
  TL0  = 0xFE;
	ET0 = 1;
	TR0 = 1;
}
void stopbuzz()
{
	ET0 = 0;
	TR0 = 0;
}
void InterruptTimer0() interrupt 1
{
    TH0 = TORH;  
    TL0 = TORL;
    BUZZ = ~BUZZ; 
}