延时的呼吸灯，这个亮度更均匀一点

#include<reg52.h>

sbit P20 = P2^0;
sbit P21 = P2^1;
sbit P22 = P2^2;
sbit ENLED = P1^1;

void Delay(unsigned int t)
{
while(t--);
}

void main()
{
unsigned int T=1500;
unsigned int Toff=0;

ENLED = 0;
P20 = 0;
P21 = 1;
P22 = 1;

while(1)
{
  for(Toff=0;Toff<T;Toff++)
  {
   P0=0;
   Delay(Toff);
   P0=0xFF;
   Delay(T-Toff);
  }
  for(Toff=1500;Toff>0;Toff--)
  {
    P0=0;
   Delay(Toff);
   P0=0xFF;
   Delay(T-Toff);
  }
}
}