原创 RC6格式遥控码的另外一种解码方法

考虑了另外一种解码方法，解码程序在定时中断中执行，定时中断设置成200us中断，在中断程序中扫描I/O，测量遥控信号低电平和高电平的时间。有几个关键变量：ir_ltime-低电平时间，ir_htime-高电平时间，bit_over-位变量，指示一位数据是否处理完。

RC6格式的0，1波形如下：

1位数据“<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />0”“1”的周期是888us，高低电平分别是444us，奇偶位的周期是2*888us，高低电平分别是2*444us。

分析RC6格式，可以得到下面的规律，就是解码原理：

1、  如果低电平是窄的，且bit_over=1,那么bit_over=0,当前位为1，ir_bit++。

2、  如果低电平是窄的，且bit_over=0，那么bit_over=1，其它不做处理。

3、  如果低电平是宽的，且bit_over=1，是错误码。

4、  如果低电平是宽的，且bit_over=0，那么bit_over=0，当前位为1，ir_bit++。

5、  如果高电平是窄的，且bit_over=1,那么bit_over=0,当前位为0，ir_bit++。

6、  如果高电平是窄的，且bit_over=0，那么bit_over=1，其它不做处理。

7、  如果高电平是宽的，且bit_over=1，是错误码。

8、  如果高电平是宽的，且bit_over=0，那么bit_over=0，当前位为0，ir_bit++。

9、  奇偶校验位的电平宽度是其他位电平宽度的2倍，在程序中单独处理。

解码程序如下：

/*

定时器0中断函数

中断间隔：200us

*/

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

void Isr_Timer0()

{

shift_ir:

       if(ir_shift_flag)

       {

              ir_shift_flag = 0;   

           _rlc(&ir_data0);

           _rlc(&ir_data1);

           _rlc(&ir_data2);

         if(ir_bit >= 21)

         { 

             if((ir_usercode == ir_data1) && (ir_value == ir_data0))

                    {

                           ir_ok = 1;

                    }

                    else

                    {    

                    ir_usercode = ir_data1;

                    ir_value = ir_data0;

                }

err_ir:

           ir_head = 0;

           ir_bit = 0;

           ir_data0 = 0;

           ir_data1 = 0;

           ir_data2 = 0;

           bit_over = 0;

           ir_shift_flag = 0; 

         } 

           return;

        }  

       ir_ltime++;

       ir_htime++;

       if(IR_IN)

       {

              if(!ir_pin_level)

              {

                     ir_pin_level = 1;   //ir电平从低变高

                     ir_ltime_temp = ir_ltime;

                     ir_htime = 0;

                     if(ir_head)

                     {

                            if(ir_ltime > 3)

                            {

                                   if(bit_over)

                                          goto err_ir;

                                   else

                                   {

                                          if(ir_bit == 5)

                                          {

                                                 if(ir_ltime > 5)     //判断奇偶位为0时的低电平

                                                 {

                                             _c = 1;

                                             ir_bit++;

                                             ir_shift_flag = 1;

                                             goto shift_ir;

                                       }

                                       else

                                       {

                                              bit_over = 1;

                                       }

                                      }

                                      else

                                      {

                                        _c = 1;

                                             ir_bit++;

                                             ir_shift_flag = 1;

                                             goto shift_ir;

                                           }   

                                   }

                            }

                            else

                            {

                                   if(bit_over)

                                   {

                                          bit_over = 0;

                                          _c = 1;

                                          ir_bit++;

                                          ir_shift_flag = 1;

                                          goto shift_ir;

                                   }

                                   else

                                          bit_over = 1;

                            }                                                                   

                     }

              }

       }

       else

       {

              if(ir_pin_level)

              {

                     ir_pin_level = 0; //ir电平从高变低

                     ir_htime_temp = ir_htime;

                     ir_ltime = 0;   

                     if(ir_head)

                     {

                            if(ir_htime > 3)

                            {

                                   if(bit_over)

                                   {

                                          if(ir_bit == 4)

                                          {

                                                 bit_over = 0;         //判断奇偶位是0时的高电平

                                                        _c = 0;

                                              ir_bit++;

                                              ir_shift_flag = 1;

                                              goto shift_ir;

                                            }

                                           else

                                                goto err_ir;

                                          }

                                   else

                                   {

                                          if(ir_bit == 5)

                                          {

                                                 if(ir_htime < 5)       //判断奇偶校验位是1时的高电平

                                                 {

                                                        bit_over = 1;

                                                 }

                                                 else

                                           {

                                                       _c = 0;

                                              ir_bit++;

                                              ir_shift_flag = 1;

                                              goto shift_ir;

                                            }

                                          }

                                          else

                                          {

                                                 _c = 0;

                                              ir_bit++;

                                              ir_shift_flag = 1;

                                              goto shift_ir;

                                            }

                                   }

                            }

                            else

                            {

                                   if(bit_over)

                                   {

                                          bit_over = 0;

                                          _c = 0;

                                          ir_bit++;

                                          ir_shift_flag = 1;

                                          goto shift_ir;

                                   }

                                   else

                                          bit_over = 1;                                     

                            }           

                     }

                     else

                     {

                            if((ir_ltime_temp > 11) && (ir_ltime_temp < 16))             

                            {

                                   ir_head = 1;   //检测到头码

                                   bit_over = 1;

                            }

                            else

                                   goto err_ir;

                     }                         

             }    

      }           

}

这种解码方式占用单片机资源少，而且灵敏度高，不会因为遥控波形的高低电平时间的少量偏差检测到误码。