adds an example of writing a wav file

Author: stephenhensley

examples/WavWriter/CMakeLists.txt

@@ -0,0 +1,3 @@
+set(FIRMWARE_NAME WavWriter)
+set(FIRMWARE_SOURCES WavWriter.cpp)
+include(DaisyProject)

examples/WavWriter/Makefile

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+# Project Name
+TARGET = WavWriter
+
+# Sources
+CPP_SOURCES = WavWriter.cpp
+
+USE_FATFS=1
+
+# Library Locations
+LIBDAISY_DIR = ../..
+
+# Core location, and generic Makefile.
+SYSTEM_FILES_DIR = $(LIBDAISY_DIR)/core
+include $(SYSTEM_FILES_DIR)/Makefile

examples/WavWriter/WavWriter.cpp

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+/** Generation of a simple Audio signal */
+#include "daisy_seed.h"
+#include <cmath>
+
+/** This prevents us from having to type "daisy::" in front of a lot of things. */
+using namespace daisy;
+
+static constexpr float  kTargetSr     = 48000.f;
+static constexpr size_t kTransferSize = 16384;
+
+/** Global Hardware access */
+DaisySeed                hw;
+SdmmcHandler             sdmmc;
+FatFSInterface           fsi;
+WavWriter<kTransferSize> wav_writer;
+
+/** Basic Fixed-frequency oscillator */
+struct SimpleOsc
+{
+    static constexpr float kTargetFreq = 220.f;
+    static constexpr float kSignalIncrement
+        = (M_TWOPI * kTargetFreq) * (1.f / kTargetSr);
+    float phs_;
+    SimpleOsc() : phs_(0.f) {}
+
+    inline float RenderSample()
+    {
+        float signal = sin(phs_) * 0.5f;
+        phs_ += kSignalIncrement;
+        if(phs_ > M_TWOPI)
+            phs_ -= M_TWOPI;
+        return signal;
+    }
+};
+
+int main(void)
+{
+    /** Initialize our hardware */
+    hw.Init();
+
+    /** Set up SD Card */
+    SdmmcHandler::Config sd_cfg;
+    sd_cfg.Defaults();
+    sd_cfg.width = SdmmcHandler::BusWidth::BITS_1;
+    sdmmc.Init(sd_cfg);
+    FatFSInterface::Config fsi_cfg;
+    fsi_cfg.media = FatFSInterface::Config::MEDIA_SD;
+    fsi.Init(fsi_cfg);
+    if(f_mount(&fsi.GetSDFileSystem(), "/", 0) != FR_OK)
+    {
+        while(1)
+        {
+            hw.SetLed((System::GetNow() & 127) > 63);
+        }
+    }
+    hw.SetLed(true);
+
+    /** Set up WAV File */
+    WavWriter<kTransferSize>::Config cfg;
+    cfg.bitspersample = 16;
+    cfg.channels      = 2;
+    cfg.samplerate    = kTargetSr;
+    wav_writer.Init(cfg);
+
+    /** Prepare to record a 1s 220Hz Audio File */
+    SimpleOsc oscillator;
+    size_t    duration_sec      = 1;
+    size_t    duration_in_samps = duration_sec * kTargetSr;
+
+    wav_writer.OpenFile("ExampleWavFile.wav");
+    for(size_t i = 0; i < duration_in_samps; i++)
+    {
+        // If recording Realtime Audio:
+        // The rendering/sampling should occur in the realtime audio interrupt
+        float sample            = oscillator.RenderSample();
+        float samps_to_write[2] = {sample, sample};
+        wav_writer.Sample(samps_to_write);
+
+        // The actual DiskIO should happen outside of the realtime audio interrupt
+        // For offline-rendering, it is okay to do this check on every sample.
+        wav_writer.Write();
+    }
+    // Flush and Close
+    wav_writer.SaveFile();
+
+    while(1)
+    {
+        // Blink Afterwards to show success
+        hw.SetLed((System::GetNow() & 511) > 255);
+    }
+}