51单片机软件产生PWM驱动直流电机，频率占空比可调

#include
#define uchar unsigned char
#define uint unsigned int

sbit cs1=P1^0;
sbit cs2=P1^1;
sbit cs3=P1^2;
sbit cs4=P1^3;

sbit start=P2^1;
sbit turn=P2^0;

uint s,n=500;
uint m=500;
bit val=0;
bit flag=0;

uchar code tab[]={
0xc0,0xf9,0xa4,0xb0,
0x99,0x92,0x82,0xf8,
0x80,0x90
};
uchar code tabpoint[]={
0x40,0x79,0x24,0x30,
0x19,0x12,0x02,0x78,
0x00,0x10
};

void delay(uint ms)
{
uint i,j;
for (i=ms;i>0;i--)
for (j=110;j>0;j--);
}

void delayus(uint us)
{
while(--us);
}

void displayday()
{

P0=tab[n/1000];
cs1=0;
delayus(20);
cs1=1;
P0=0xff;

P0=tabpoint[n%1000/100];
cs2=0;
delayus(20);
cs2=1;
P0=0xff;

P0=tab[n%100/10];
cs3=0;
delayus(20);
cs3=1;
P0=0xff;

P0=tab[n%10];
cs4=0;
delayus(20);
cs4=1;
P0=0xff;
}

void displaynight()
{

P0=tab[m/1000];
cs1=0;
delayus(20);
cs1=1;
P0=0xff;

P0=tabpoint[m%1000/100];
cs2=0;
delayus(20);
cs2=1;
P0=0xff;

P0=tab[m%100/10];
cs3=0;
delayus(20);
cs3=1;
P0=0xff;

P0=tab[m%10];
cs4=0;
delayus(20);
cs4=1;
P0=0xff;
}
void displayoff()
{
P0=0xff;
cs1=cs2=cs3=cs4=0;
}

void main()
{
TMOD=0x02;
TH0=(256-1)/256;
TL0=(256-1)%256;
EA=1;
ET0=1;
TR0=1;
EX0=1;
IT0=0;
while(1)
{
if (start==0&&flag==0)
{
displayday();
}
if (start==0&&flag==1)
{
displaynight();
}
if (start==1)
{
displayoff();
}
}
}

void jisuan() interrupt 0
{
s++;
delay(1);
if (val==1&&s==1000)
{
n=n+130;
m=m+200;
s=0;
if (n==9990)
{
n=0;
val=0;
}
if (m==9900)
{
m=0;
val=0;
}
}
if (s==3000)
{
val=1;
s=0;
}

}

void jiance() interrupt 1
{
if (turn==0)
{
delayus(20);
if (turn==0)
{
flag=!flag;
}

}
}