PID rework - use watts

workspace/TS100/inc/history.hpp

@@ -0,0 +1,41 @@
+/*
+ * history.hpp
+ *
+ *  Created on: 28 Oct, 2018
+ *     Authors: Ben V. Brown, David Hilton
+ */
+
+#ifndef HISTORY_HPP_
+#define HISTORY_HPP_
+
+#include <stdint.h>
+
+// max size = 127
+template <class T=uint16_t, uint8_t SIZE=15>
+struct history {
+    static const uint8_t size = SIZE;
+	T buf[size];
+	int32_t sum;
+	uint8_t loc;
+
+	void update(T const val) {
+		// step backwards so i+1 is the previous value.
+		loc = (size+loc-1) % size;
+
+		sum -= buf[loc];
+		sum += val;
+		buf[loc] = val;
+	}
+
+	T operator[] (uint8_t i) const {
+		// 0 = newest, size-1 = oldest.
+		i = (i+loc) % size;
+		return buf[i];
+	}
+
+	T average() const {
+		return sum / size;
+	}
+};
+
+#endif  /* HISTORY_HPP_ */