Introduce multitrack audio playback capability

Author: finneyj

inc/MicroBitAudio.h

@@ -28,6 +28,7 @@ DEALINGS IN THE SOFTWARE.
 #include "NRF52PWM.h"
 #include "SoundEmojiSynthesizer.h"
 #include "SoundExpressions.h"
+#include "SampleSource.h"
 #include "Mixer2.h"
 #include "SoundOutputPin.h"
 #include "StreamNormalizer.h"
@@ -39,12 +40,15 @@ DEALINGS IN THE SOFTWARE.
 #define MICROBIT_AUDIO_STATUS_DEEPSLEEP       0x0001
 #define CONFIG_DEFAULT_MICROPHONE_GAIN        0.1f
 
-
 // Configurable options
 #ifndef CONFIG_AUDIO_MIXER_OUTPUT_LATENCY_US
 #define CONFIG_AUDIO_MIXER_OUTPUT_LATENCY_US              (uint32_t) ((CONFIG_MIXER_BUFFER_SIZE/2) * (1000000.0f/44100.0f))
 #endif
 
+#ifndef CONFIG_AUDIO_INPUT_CHANNELS
+#define CONFIG_AUDIO_INPUT_CHANNELS                       4
+#endif
+
 namespace codal
 {
     /**
@@ -61,6 +65,7 @@ namespace codal
         StreamSplitter          *rawSplitter;   // Stream Splitter instance (raw input)
         LevelDetectorSPL        *levelSPL;      // Level Detector SPL instance
         LowPassFilter           *micFilter;     // Low pass filter to remove high frequency noise on the mic
+        SampleSource            *sampleSource[CONFIG_AUDIO_INPUT_CHANNELS]; // multichannel sample playback capability
 
         private:
         volatile bool micEnabled;               // State of on board mic

inc/SampleSource.h

@@ -0,0 +1,37 @@
+#ifndef SAMPLE_SOURCE_H
+#define SAMPLE_SOURCE_H
+
+#include "MemorySource.h"
+#include "DataStream.h"
+#include "Mixer2.h"
+
+namespace codal
+{
+    class SampleSource : public MemorySource
+    {
+        private:
+        Mixer2 &mixer;
+        float sampleRate;
+        float sampleRange;
+        MixerChannel *channel;
+
+        public:
+            /**
+             * Constructor.
+             * Creates an empty sample source with a Mixer.
+             * = CONFIG_MIXER_DEFAULT_SAMPLERATE
+             */
+            SampleSource(Mixer2 &mixer, float sampleRate, float sampleRange);
+
+            /**
+             * Destructor
+             * Removes all resources held by the instance
+             */
+            ~SampleSource();
+
+            void setSampleRate(float sampleRate);
+
+            void setVolume(float volume);
+    };
+}
+#endif

model/MicroBit.h

@@ -67,6 +67,7 @@ DEALINGS IN THE SOFTWARE.
 #include "StreamNormalizer.h"
 #include "LevelDetector.h"
 #include "LevelDetectorSPL.h"
+#include "SampleSource.h"
 #include "PulseIn.h"
 #include "neopixel.h"
 

source/MicroBitAudio.cpp

@@ -88,6 +88,10 @@ MicroBitAudio::MicroBitAudio(NRF52Pin &pin, NRF52Pin &speaker, NRF52ADC &adc, NR
 
     //Initilise stream splitter
     splitter = new StreamSplitter(processor->output, DEVICE_ID_SPLITTER);
+
+    // Create audio input channels
+    for (int i=0; i<CONFIG_AUDIO_INPUT_CHANNELS; i++)
+        sampleSource[i] = new SampleSource(mixer, 11000, 255);
 }
 
 void MicroBitAudio::periodicCallback()

source/SampleSource.cpp

@@ -0,0 +1,28 @@
+#include "SampleSource.h"
+#include "CodalDmesg.h"
+
+using namespace codal;
+
+SampleSource::SampleSource(Mixer2 &mixer, float sampleRate, float sampleRange) : MemorySource(), mixer(mixer)
+{
+    this->sampleRate = sampleRate;
+    this->sampleRange = sampleRange;
+    this->channel = this->mixer.addChannel(*this, sampleRate, sampleRange);
+    connect(*channel);
+}
+
+SampleSource::~SampleSource()
+{
+    this->mixer.removeChannel(this->channel);
+}
+
+void SampleSource::setSampleRate(float sr)
+{
+    this->sampleRate = sr;
+    this->channel->setSampleRate(sr);
+}
+
+void SampleSource::setVolume(float volume)
+{
+    this->channel->setVolume(volume);
+}