Add a 2nd example progrma

src/main_testtone.cc

@@ -0,0 +1,43 @@
+#include "daisy_seed.h"
+#include "daisysp.h"
+
+namespace ld = daisy;
+namespace dsp = daisysp;
+
+static ld::DaisySeed hardware;
+static dsp::Oscillator osc;
+
+void AudioCallback(
+    ld::AudioHandle::InterleavingInputBuffer in,
+    ld::AudioHandle::InterleavingOutputBuffer out,
+    size_t size)
+{
+    float osc_out;
+    osc.SetFreq(1000);
+    for (size_t i = 0; i < size; i += 2) {
+        osc.SetAmp(1.0);
+        osc_out = osc.Process();
+        osc_out *= 0.01;
+        out[i] = osc_out;
+        out[i + 1] = osc_out;
+    }
+}
+
+
+int main(void)
+{
+    hardware.Configure();
+    hardware.Init();
+    hardware.SetAudioBlockSize(4);
+
+    float samplerate = hardware.AudioSampleRate();
+
+    osc.Init(samplerate);
+    osc.SetWaveform(osc.WAVE_SIN);
+    osc.SetAmp(1.f);
+    osc.SetFreq(1000);
+
+    hardware.StartAudio(AudioCallback);
+
+    while (true) {}
+}