1 files changed, 28 insertions, 0 deletions
diff --git a/src/components/heartrate/Ptagc.cpp b/src/components/heartrate/Ptagc.cpp
new file mode 100644
index 0000000..dd7c441
--- /dev/null
+++ b/src/components/heartrate/Ptagc.cpp
@@ -0,0 +1,28 @@
+/*
+  SPDX-License-Identifier: LGPL-3.0-or-later
+  Original work Copyright (C) 2020 Daniel Thompson
+  C++ port Copyright (C) 2021 Jean-François Milants
+*/
+
+#include <cmath>
+#include "Ptagc.h"
+
+using namespace Pinetime::Controllers;
+
+/** Original implementation from wasp-os : https://github.com/daniel-thompson/wasp-os/blob/master/wasp/ppg.py */
+Ptagc::Ptagc(float start, float decay, float threshold) : peak{start}, decay{decay}, boost{1.0f/decay}, threshold{threshold} {
+
+}
+
+float Ptagc::Step(float spl) {
+  if(std::abs(spl) > peak)
+    peak *= boost;
+  else
+    peak *= decay;
+
+  if((spl > (peak * threshold)) || (spl < (peak * -threshold)))
+    return 0.0f;
+
+  spl = 100.0f * spl / (2.0f * peak);
+  return spl;
+}