f411_vr_dpcm.c

用c8051f410和FLASH（SPI接口）实现的数字录音机。

               {
                  dpcm_code = 57;
               }
               // fifth tier
               else
               {
                  dpcm_code = 56;
               }
            }
         }
      }
      // second tier
      else
      {
         // third tier
         if (sample_diff_us >= quant20)
         {
            // fourth tier
            if (sample_diff_us >= quant22)
            {
               // fifth tier
               if (sample_diff_us >= quant23)
               {
                  dpcm_code = 55;
               }
               // fifth tier
               else
               {
                  dpcm_code = 54;
               }
            }
            // fourth tier
            else
            {
               // fifth tier
               if (sample_diff_us >= quant21)
               {
                  dpcm_code = 53;
               }
               // fifth tier
               else
               {
                  dpcm_code = 52;
               }
            }
         }
         // third tier
         else
         {
            // fourth tier
            if (sample_diff_us >= quant18)
            {
               // fifth tier
               if (sample_diff_us >= quant19)
               {
                  dpcm_code = 51;
               }
               // fifth tier
               else
               {
                  dpcm_code = 50;
               }
            }
            // fourth tier
            else
            {
               // fifth tier
               if (sample_diff_us >= quant17)
               {
                  dpcm_code = 49;
               }
               // fifth tier
               else
               {
                  dpcm_code = 48;
               }
            }
         }
      }
   }
   // first tier
   else
   {
      // second tier
      if (sample_diff_us >= quant8)
      {
         // third tier
         if (sample_diff_us >= quant12)
         {
            // fourth tier
            if (sample_diff_us >= quant14)
            {
               // fifth tier
               if (sample_diff_us >= quant15)
               {
                  dpcm_code = 47;
               }
               // fifth tier
               else
               {
                  dpcm_code = 46;
               }
            }
            // fourth tier
            else
            {
               // fifth tier
               if (sample_diff_us >= quant13)
               {
                  dpcm_code = 45;
               }
               // fifth tier
               else
               {
                  dpcm_code = 44;
               }
            }
         }
         // third tier
         else
         {
            // fourth tier
            if (sample_diff_us >= quant10)
            {
               // fifth tier
               if (sample_diff_us >= quant11)
               {
                  dpcm_code = 43;
               }
               // fifth tier
               else
               {
                  dpcm_code = 42;
               }
            }
            // fourth tier
            else
            {
               // fifth tier
               if (sample_diff_us >= quant9)
               {
                  dpcm_code = 41;
               }
               // fifth tier
               else
               {
                  dpcm_code = 40;
               }
            }
         }
      }
      // second tier
      else
      {
         // third tier
         if (sample_diff_us >= quant4)
         {
            // fourth tier
            if (sample_diff_us >= quant6)
            {
               // fifth tier
               if (sample_diff_us >= quant7)
               {
                  dpcm_code = 39;
               }
               // fifth tier
               else
               {
                  dpcm_code = 38;
               }
            }
            // fourth tier
            else
            {
               // fifth tier
               if (sample_diff_us >= quant5)
               {
                  dpcm_code = 37;
               }
               // fifth tier
               else
               {
                  dpcm_code = 36;
               }
            }
         }
         // third tier
         else
         {
            // fourth tier
            if (sample_diff_us >= quant2)
            {
               // fifth tier
               if (sample_diff_us >= quant3)
               {
                  dpcm_code = 35;
               }
               // fifth tier
               else
               {
                  dpcm_code = 34;
               }
            }
            // fourth tier
            else
            {
               // fifth tier
               if (sample_diff_us >= quant1)
               {
                  dpcm_code = 33;
               }
               // fifth tier
               else
               {
                  dpcm_code = 32;
               }
            }
         }
      }
   }

   // convert the DPCM code to its 2's compliment if the original sample
   // difference was negative
   // For example, 41 (101001), which represents a difference of 60, 2's
   // complimented becomes 23 (010111), which represents a difference of -60
   if (sample_diff < 0)
   {
      dpcm_code = ~dpcm_code + 1;     // use the 2's compliment of the dpcm
                                      // code
      dpcm_code &= 0x3F;              // use only the 6 LSBs for the dpcm code
   }

   return dpcm_code;
}

//-----------------------------------------------------------------------------
// DPCM_Decode
//-----------------------------------------------------------------------------
//
// Return Value :
//   1)  short predicted_value - the signed and quantized difference between
//                      the predicted_value and the ADC sample, which is used
//                      create the predicted_value for the next DPCM cycle
//                      range is: -4096 to 4095 (difference of 12-bit values)
// Parameters   :
//   1)  char dpcm_code - the 6-bit code indicating the quantized difference
//                      between the old_prediction and the current sample value
//                      range is positive range of 6-bit value: 0 to 63
//
// Decode the DPCM code to a signed difference between the current predicted
// value and the next.
//
// NOTE: the calling function must have the same register context, so it must
// either have the keyword "using 2" or all "using 2" keywords need to be
// removed
short DPCM_Decode (unsigned char dpcm_code) using 2
{
   return Q_VALUES[dpcm_code];
}

//-----------------------------------------------------------------------------
// End Of File
//-----------------------------------------------------------------------------