diff --git a/libraries/PDM/src/PDM.h b/libraries/PDM/src/PDM.h
index c73082250..77c99d8ca 100644
--- a/libraries/PDM/src/PDM.h
+++ b/libraries/PDM/src/PDM.h
@@ -42,6 +42,7 @@ class PDMClass
   //NANO 33 BLE SENSe min 0 max 80
   void setGain(int gain);
   void setBufferSize(int bufferSize);
+  size_t getBufferSize();
 
 // private:
   void IrqHandler(bool halftranfer);
@@ -58,7 +59,7 @@ class PDMClass
   int _init;
 
   PDMDoubleBuffer _doubleBuffer;
-  
+
   void (*_onReceive)(void);
 };
 
diff --git a/libraries/PDM/src/stm32/PDM.cpp b/libraries/PDM/src/stm32/PDM.cpp
index 69ce30b6b..241da2840 100644
--- a/libraries/PDM/src/stm32/PDM.cpp
+++ b/libraries/PDM/src/stm32/PDM.cpp
@@ -29,6 +29,7 @@ extern "C" {
 }
 
 extern "C" uint16_t *g_pcmbuf;
+static PDMClass *_instance = NULL;
 
 PDMClass::PDMClass(int dinPin, int clkPin, int pwrPin) :
   _dinPin(dinPin),
@@ -40,10 +41,12 @@ PDMClass::PDMClass(int dinPin, int clkPin, int pwrPin) :
   _samplerate(-1),
   _init(-1)
 {
+  _instance = this;
 }
 
 PDMClass::~PDMClass()
 {
+  _instance = NULL;
 }
 
 int PDMClass::begin(int channels, int sampleRate) {
@@ -63,6 +66,10 @@ int PDMClass::begin(int channels, int sampleRate) {
     i2c.write(8 << 1, data, sizeof(data));
   }
 
+  if(_instance != this) {
+    return 0;
+  }
+
   _channels = channels;
   _samplerate = sampleRate;
 
@@ -70,7 +77,10 @@ int PDMClass::begin(int channels, int sampleRate) {
     _gain = 24;
   }
 
-  if(py_audio_init(channels, sampleRate, _gain, 0.9883f)) {
+  g_pcmbuf = (uint16_t*)_doubleBuffer.data();
+  _doubleBuffer.swap(0);
+
+  if(py_audio_init(channels, sampleRate, gain_db, 0.9883f)) {
     py_audio_start_streaming();
     _init = 1;
     return 1;
@@ -99,6 +109,9 @@ int PDMClass::read(void* buffer, size_t size)
 void PDMClass::onReceive(void(*function)(void))
 {
   _onReceive = function;
+  if(_instance != this) {
+    _instance = this;
+  }
 }
 
 void PDMClass::setGain(int gain)
@@ -114,27 +127,44 @@ void PDMClass::setBufferSize(int bufferSize)
   _doubleBuffer.setSize(bufferSize);
 }
 
+size_t PDMClass::getBufferSize()
+{
+  return _doubleBuffer.getSize();
+}
+
+#define HALF_TRANSFER_SIZE  (64*_channels)
+static int g_pcmbuf_size=0;
+
 void PDMClass::IrqHandler(bool halftranfer)
 {
-  if (_doubleBuffer.available() == 0) {
-    g_pcmbuf = (uint16_t*)_doubleBuffer.data();
+  if (g_pcmbuf_size < _doubleBuffer.getSize()) {
     audio_pendsv_callback();
-    _doubleBuffer.swap(_doubleBuffer.availableForWrite());
-  }
-
-  if (_onReceive) {
-      _onReceive();
+    g_pcmbuf += (HALF_TRANSFER_SIZE/2);
+    g_pcmbuf_size += HALF_TRANSFER_SIZE;
+
+    if(g_pcmbuf_size == _doubleBuffer.getSize()) {
+      _doubleBuffer.swap(g_pcmbuf_size);
+      g_pcmbuf = (uint16_t*)_doubleBuffer.data();
+      g_pcmbuf_size = 0;
+      if (_onReceive) {
+        _onReceive();
+      }
+    }
   }
 }
 
 extern "C" {
 void PDMIrqHandler(bool halftranfer)
 {
-  PDM.IrqHandler(halftranfer);
+  _instance->IrqHandler(halftranfer);
 }
 
 void PDMsetBufferSize(int size) {
-  PDM.setBufferSize(size);
+  _instance->setBufferSize(size);
+}
+
+size_t PDMgetBufferSize() {
+  return _instance.getBufferSize();
 }
 }
 
diff --git a/libraries/PDM/src/stm32/audio.c b/libraries/PDM/src/stm32/audio.c
index 8d8d037ce..3d585c289 100644
--- a/libraries/PDM/src/stm32/audio.c
+++ b/libraries/PDM/src/stm32/audio.c
@@ -303,8 +303,11 @@ int py_audio_init(size_t channels, uint32_t frequency, int gain_db, float highpa
         PDM_Filter_setConfig(&PDM_FilterHandler[i], &PDM_FilterConfig[i]);
     }
 
-    PDMsetBufferSize(samples_per_channel * g_o_channels * sizeof(int16_t));
-    //g_pcmbuf = malloc(samples_per_channel * g_channels * sizeof(int16_t));
+    uint32_t min_buff_size = samples_per_channel * g_o_channels * sizeof(int16_t);
+    uint32_t buff_size = PDMgetBufferSize();
+    if(buff_size < min_buff_size) {
+      PDMsetBufferSize(min_buff_size);
+    }
 
     return 1;
 }
diff --git a/libraries/PDM/src/utility/PDMDoubleBuffer.cpp b/libraries/PDM/src/utility/PDMDoubleBuffer.cpp
index 2e6a4c2c7..d3924c1f0 100644
--- a/libraries/PDM/src/utility/PDMDoubleBuffer.cpp
+++ b/libraries/PDM/src/utility/PDMDoubleBuffer.cpp
@@ -37,6 +37,11 @@ void PDMDoubleBuffer::setSize(int size)
   reset();
 }
 
+size_t PDMDoubleBuffer::getSize()
+{
+  return _size;
+}
+
 void PDMDoubleBuffer::reset()
 {
   _buffer[0] = (uint8_t*)realloc(_buffer[0], _size);
diff --git a/libraries/PDM/src/utility/PDMDoubleBuffer.h b/libraries/PDM/src/utility/PDMDoubleBuffer.h
index 1544af5bf..7eb8a614a 100644
--- a/libraries/PDM/src/utility/PDMDoubleBuffer.h
+++ b/libraries/PDM/src/utility/PDMDoubleBuffer.h
@@ -31,6 +31,7 @@ class PDMDoubleBuffer
   virtual ~PDMDoubleBuffer();
 
   void setSize(int size);
+  size_t getSize();
 
   void reset();