Merge pull request #349 from pennam/pdm_cut

Portenta: PDM: cut out unusable starting PDM samples.

Author: facchinm

Diff for: libraries/PDM/src/PDM.h

@@ -58,6 +58,8 @@ class PDMClass
   int _gain;
   int _init;
 
+  int _cutSamples;
+
   PDMDoubleBuffer _doubleBuffer;
 
   void (*_onReceive)(void);

Diff for: libraries/PDM/src/nrf52/PDM.cpp

@@ -43,7 +43,8 @@ PDMClass::PDMClass(int dinPin, int clkPin, int pwrPin) :
   _gain(-1),
   _channels(-1),
   _samplerate(-1),
-  _init(-1)
+  _init(-1),
+  _cutSamples(0)
 {
 }
 

Diff for: libraries/PDM/src/rp2040/PDM.cpp

@@ -53,7 +53,8 @@ PDMClass::PDMClass(int dinPin, int clkPin, int pwrPin) :
   _gain(-1),
   _channels(-1),
   _samplerate(-1),
-  _init(-1)
+  _init(-1),
+  _cutSamples(100)
 {
 }
 
@@ -138,6 +139,8 @@ int PDMClass::begin(int channels, int sampleRate)
     true                // Start immediately
   );
 
+  _cutSamples = 100;
+
   _init = 1;
 
   return 1;
@@ -190,8 +193,6 @@ void PDMClass::setBufferSize(int bufferSize)
 
 void PDMClass::IrqHandler(bool halftranfer)
 {
-  static int cutSamples = 100;
-
   // Clear the interrupt request.
   dma_hw->ints0 = 1u << dmaChannel; 
   // Restart dma pointing to the other buffer 
@@ -210,9 +211,9 @@ void PDMClass::IrqHandler(bool halftranfer)
     Open_PDM_Filter_64(rawBuffer[rawBufferIndex], finalBuffer, 1, &filter);
   }
 
-  if (cutSamples) {
-    memset(finalBuffer, 0, cutSamples);
-    cutSamples = 0;
+  if (_cutSamples) {
+    memset(finalBuffer, 0, _cutSamples);
+    _cutSamples = 0;
   }
 
   // swap final buffer and raw buffers' indexes

Diff for: libraries/PDM/src/stm32/PDM.cpp

@@ -39,7 +39,8 @@ PDMClass::PDMClass(int dinPin, int clkPin, int pwrPin) :
   _gain(-1),
   _channels(-1),
   _samplerate(-1),
-  _init(-1)
+  _init(-1),
+  _cutSamples(4)
 {
   _instance = this;
 }
@@ -80,6 +81,8 @@ int PDMClass::begin(int channels, int sampleRate) {
   g_pcmbuf = (uint16_t*)_doubleBuffer.data();
   _doubleBuffer.swap(0);
 
+  _cutSamples = 4 * channels;
+
   if(py_audio_init(channels, sampleRate, _gain, 0.9883f)) {
     py_audio_start_streaming();
     _init = 1;
@@ -146,8 +149,12 @@ void PDMClass::IrqHandler(bool halftranfer)
       _doubleBuffer.swap(g_pcmbuf_size);
       g_pcmbuf = (uint16_t*)_doubleBuffer.data();
       g_pcmbuf_size = 0;
-      if (_onReceive) {
-        _onReceive();
+      if(_cutSamples == 0) {
+        if (_onReceive) {
+          _onReceive();
+        }
+      } else {
+          _cutSamples--;
       }
     }
   }