while()
            {
                test();             //测量转换一次
                  if(i==0)
                     for(;;)
                        {    j=CO;
                            if(j==0)
                             {
                                n++;
                              }
                             tongdao(n);
                                if(n>7)
                                  n=0;     
                                if(i==0) break;                           
                            }            
                  else
                  {
                    scan();       //显示八个通道值一次
                  }
             }
    }
//