PDM library re-port (#1160)

See #1156

Author: TomKong666

libraries/PDM/src/PDM.h

@@ -38,6 +38,7 @@ 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();
@@ -56,6 +57,8 @@ class PDMClass {
     int _gain;
     int _init;
 
+    int _cutSamples;
+
     // Hardware peripherals used
     uint _dmaChannel;
     PIO _pio;

libraries/PDM/src/rp2040/PDM.cpp

@@ -20,7 +20,7 @@ uint8_t rawBuffer1[RAW_BUFFER_SIZE];
 uint8_t* rawBuffer[2] = {rawBuffer0, rawBuffer1};
 volatile int rawBufferIndex = 0;
 
-int decimation = 64;
+int decimation = 128;
 
 // final buffer is the one to be filled with PCM data
 int16_t* volatile finalBuffer;
@@ -45,6 +45,7 @@ PDMClass::PDMClass(int dinPin, int clkPin, int pwrPin) :
     _channels(-1),
     _samplerate(-1),
     _init(-1),
+    _cutSamples(100),
     _dmaChannel(0),
     _pio(nullptr),
     _smIdx(-1),
@@ -55,6 +56,12 @@ PDMClass::~PDMClass() {
 }
 
 int PDMClass::begin(int channels, int sampleRate) {
+
+    if (_init == 1) {
+        //ERROR: please call end first
+        return 0;
+    }
+
     //_channels = channels; // only one channel available
 
     // clear the final buffers
@@ -63,6 +70,18 @@ int PDMClass::begin(int channels, int sampleRate) {
     int finalBufferLength = _doubleBuffer.availableForWrite() / sizeof(int16_t);
     _doubleBuffer.swap(0);
 
+    // The mic accepts an input clock from 1.2 to 3.25 Mhz
+    // Setup the decimation factor accordingly
+    if ((sampleRate * decimation * 2) > 3250000) {
+        decimation = 64;
+    }
+
+    // Sanity check, abort if still over 3.25Mhz
+    if ((sampleRate * decimation * 2) > 3250000) {
+        //ERROR:  Sample rate too high, the mic would glitch
+        return -1;
+    }
+
     int rawBufferLength = RAW_BUFFER_SIZE / (decimation / 8);
     // Saturate number of samples. Remaining bytes are dropped.
     if (rawBufferLength > finalBufferLength) {
@@ -71,6 +90,7 @@ int PDMClass::begin(int channels, int sampleRate) {
 
     /* Initialize Open PDM library */
     filter.Fs = sampleRate;
+    filter.MaxVolume = 1;
     filter.nSamples = rawBufferLength;
     filter.LP_HZ = sampleRate / 2;
     filter.HP_HZ = 10;
@@ -88,7 +108,7 @@ int PDMClass::begin(int channels, int sampleRate) {
 
     if (!_pdmPgm.prepare(&_pio, &_smIdx, &_pgmOffset)) {
         // ERROR, no free slots
-        return -1;
+        return 0;
     }
     pdm_pio_program_init(_pio, _smIdx, _pgmOffset, _clkPin, _dinPin, clkDiv);
 
@@ -118,14 +138,29 @@ int PDMClass::begin(int channels, int sampleRate) {
                           true                // Start immediately
                          );
 
+    _cutSamples = 100;
+
     _init = 1;
 
     return 1;
 }
 
 void PDMClass::end() {
+
+    if (_init != 1) {
+        return;
+    }
+
+    dma_channel_set_irq0_enabled(_dmaChannel, false);
     dma_channel_abort(_dmaChannel);
+    dma_channel_unclaim(_dmaChannel);
+    irq_remove_handler(DMA_IRQ_0, dmaHandler);
+    pio_sm_unclaim(_pio, _smIdx);
     pinMode(_clkPin, INPUT);
+    rawBufferIndex = 0;
+    _pgmOffset = -1;
+
+    _init = 0;
 }
 
 int PDMClass::available() {
@@ -163,32 +198,32 @@ 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
     int shadowIndex = rawBufferIndex ^ 1;
     dma_channel_set_write_addr(_dmaChannel, rawBuffer[shadowIndex], true);
 
-    if (_doubleBuffer.available()) {
-        // buffer overflow, stop
-        return end();
+    if (!_doubleBuffer.available()) {
+        // fill final buffer with PCM samples
+        if (filter.Decimation == 128) {
+            Open_PDM_Filter_128(rawBuffer[rawBufferIndex], finalBuffer, 1, &filter);
+        } else {
+            Open_PDM_Filter_64(rawBuffer[rawBufferIndex], finalBuffer, 1, &filter);
+        }
+
+        if (_cutSamples) {
+            memset(finalBuffer, 0, _cutSamples);
+            _cutSamples = 0;
+        }
+
+        // swap final buffer and raw buffers' indexes
+        finalBuffer = (int16_t*)_doubleBuffer.data();
+        _doubleBuffer.swap(filter.nSamples * sizeof(int16_t));
+        rawBufferIndex = shadowIndex;
     }
 
-    // fill final buffer with PCM samples
-    Open_PDM_Filter_64(rawBuffer[rawBufferIndex], finalBuffer, 1, &filter);
-
-    if (cutSamples) {
-        memset(finalBuffer, 0, cutSamples);
-        cutSamples = 0;
-    }
-
-    // swap final buffer and raw buffers' indexes
-    finalBuffer = (int16_t*)_doubleBuffer.data();
-    _doubleBuffer.swap(filter.nSamples * sizeof(int16_t));
-    rawBufferIndex = shadowIndex;
-
     if (_onReceive) {
         _onReceive();
     }