Correct phase interpolation to correct very minor error

RadioIQMixer_F32.cpp

@@ -9,17 +9,19 @@
  * and cos of the same frequency.  The pair of mixer outputs are
  * referred to as i and q.  The conversion in frequency is either
  * up or down, and a pair of filters on i and q determine which is allow
- * to pass to the output. 
- * 
+ * to pass to the output.
+ *
  * April 2021 - Alternatively, there can be two inputs to 0 (left) and 1
  * (right) feeding the two mixers separately.  This covers all transmit
  * and receive situations.
- * 
+ *
  * The sin/cos LO is from synth_sin_cos_f32.cpp  See that for details.
- * 
+ *
  * Inputs are either real or I-Q per bool twoChannel.   Rev Apr 2021
- * 
+ *
  * MIT License,  Use at your own risk.
+ *
+ *  Rev 28 Mar 2022 Correctedslight interpolation error.  RSL
 */
 
 #include "RadioIQMixer_F32.h"
@@ -47,7 +49,7 @@ void RadioIQMixer_F32::update(void) {
 
   // Try to get a pair of blocks for the IQ output
   blockOut_i = AudioStream_F32::allocate_f32();
-  if (!blockOut_i){      // Didn't have any  
+  if (!blockOut_i){      // Didn't have any
     if(errorPrintIQM)  Serial.println("IQMIXER-ERR: No I output memory");
     AudioStream_F32::release(blockIn0);
     if(twoChannel)
@@ -78,8 +80,8 @@ void RadioIQMixer_F32::update(void) {
           a = sinTable512_f32[index];
           b = sinTable512_f32[index+1];
           // Linear interpolation and multiplying (DBMixer) with input
-          blockOut_i->data[i] = blockIn0->data[i] * (a + 0.001953125*(b-a)*deltaPhase);
- 
+          blockOut_i->data[i] = blockIn0->data[i] * (a + (b-a)*deltaPhase);
+
           /* Repeat for cosine by adding 90 degrees phase  */
           index = (index + 128) & 0x01ff;
           /* Read two nearest values of input value from the sin table */
@@ -87,9 +89,9 @@ void RadioIQMixer_F32::update(void) {
           b = sinTable512_f32[index+1];
           /* deltaPhase will be the same as used for sin  */
           if(twoChannel)
-             blockOut_q->data[i] = blockIn1->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
+             blockOut_q->data[i] = blockIn1->data[i]*(a + (b-a)*deltaPhase);
           else
-             blockOut_q->data[i] = blockIn0->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
+             blockOut_q->data[i] = blockIn0->data[i]*(a + (b-a)*deltaPhase);
        }
     }
     else {   // Do a more flexible update, i.e., not doSimple
@@ -103,8 +105,8 @@ void RadioIQMixer_F32::update(void) {
           b = sinTable512_f32[index+1];
           // We now have a sine value, so multiply with the input data and save
           // Linear interpolate sine and multiply with the input and amplitude (about 1.0)
-          blockOut_i->data[i] = amplitude_pk * blockIn0->data[i] * (a + 0.001953125*(b-a)*deltaPhase);
- 
+          blockOut_i->data[i] = amplitude_pk * blockIn0->data[i] * (a + (b-a)*deltaPhase);
+
           /* Shift forward phaseS_C  and get cos. First, the calculation of index of the table */
           phaseC = phaseS + phaseS_C;
           if (phaseC > 512.0f)  phaseC -= 512.0f;
@@ -115,9 +117,9 @@ void RadioIQMixer_F32::update(void) {
           b = sinTable512_f32[index+1];
           // Same as sin, but leave amplitude of LO at +/- 1.0
           if(twoChannel)
-             blockOut_q->data[i] = blockIn1->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
+             blockOut_q->data[i] = blockIn1->data[i]*(a + (b-a)*deltaPhase);
           else
-             blockOut_q->data[i] = blockIn0->data[i]*(a + 0.001953125*(b-a)*deltaPhase);
+             blockOut_q->data[i] = blockIn0->data[i]*(a + (b-a)*deltaPhase);
         }
     }
     AudioStream_F32::release(blockIn0);   // Done with this