First implementation of the HR sensor using 100% foss code (ported from waspos)

src/components/heartrate/Ppg.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <array>
+#include "Biquad.h"
+#include "Ptagc.h"
+
+namespace Pinetime {
+  namespace Controllers {
+    class Ppg {
+    public:
+      explicit Ppg(float spl);
+
+      int Preprocess(float spl);
+      float HeartRate();
+
+      void SetOffset(uint16_t i);
+
+    private:
+      std::array<int, 200> data;
+      size_t dataIndex = 0;
+      float offset;
+      Biquad hpf;
+      Ptagc agc;
+      Biquad lpf;
+
+
+      float ProcessHeartRate();
+    };
+  }
+}