Implement setGain() API with range 0-8

Author: giulcioffi

libraries/PDM/src/PDM.h

@@ -40,6 +40,7 @@ class PDMClass
 
   //PORTENTA_H7 min -12 max 51
   //NANO 33 BLE SENSe min 0 max 80
+  //NICLA_VISION min 0 max 8
   void setGain(int gain);
   void setBufferSize(int bufferSize);
   size_t getBufferSize();

libraries/PDM/src/nicla_vision/PDM.cpp

@@ -58,7 +58,7 @@ int PDMClass::begin(int channels, int sampleRate) {
   _samplerate = sampleRate;
 
   if (_gain == -1) {
-    _gain = 24;
+    _gain = 3;
   }
 
   g_pcmbuf = (uint16_t*)_doubleBuffer.data();
@@ -104,9 +104,7 @@ void PDMClass::onReceive(void(*function)(void))
 void PDMClass::setGain(int gain)
 {
   _gain = gain;
-  if(_init == 1) {
-    py_audio_gain_set(gain);
-  }
+  py_audio_gain_set(gain);
 }
 
 void PDMClass::setBufferSize(int bufferSize)

libraries/PDM/src/nicla_vision/audio.c

@@ -35,6 +35,8 @@ static uint32_t HAL_RCC_DFSDM1_CLK_ENABLED=0;
 
 static uint32_t DFSDM1_Init = 0;
 
+static int attenuation = 5;
+
 ALIGN_32BYTES(int32_t                      RecBuff[PDM_BUFFER_SIZE]);
 
 #define SaturaLH(N, L, H) (((N)<(L))?(L):(((N)>(H))?(H):(N)))
@@ -391,6 +393,7 @@ int py_audio_init(size_t channels, uint32_t frequency)
 
 void py_audio_gain_set(int gain_db)
 {
+  attenuation = 8 - gain_db;
 }
 
 void py_audio_deinit()
@@ -414,15 +417,15 @@ void audio_pendsv_callback(void)
         xfer_status &= ~(DMA_XFER_HALF);
 
         for (int i=0; i<PDM_BUFFER_SIZE/2; i++) {
-            ((int16_t*)g_pcmbuf)[i]     = SaturaLH((RecBuff[i] >> 8), -32768, 32767);
+            ((int16_t*)g_pcmbuf)[i]     = SaturaLH((RecBuff[i] >> attenuation), -32768, 32767);
         }
     } else if ((xfer_status & DMA_XFER_FULL)) { // Check for transfer complete.
         // Clear buffer state.
         xfer_status &= ~(DMA_XFER_FULL);
 
         for(int i = 0; i < PDM_BUFFER_SIZE/2; i++)
         {
-            ((int16_t*)g_pcmbuf)[i]     = SaturaLH((RecBuff[PDM_BUFFER_SIZE/2 + i] >> 8), -32768, 32767);
+            ((int16_t*)g_pcmbuf)[i]     = SaturaLH((RecBuff[PDM_BUFFER_SIZE/2 + i] >> attenuation), -32768, 32767);
         }
     }
 }