diff --git a/README.md b/README.md
index c01e7ea..e317dfb 100644
--- a/README.md
+++ b/README.md
@@ -71,6 +71,10 @@ Implemented are the following [trigger functions](https://en.wikipedia.org/wiki/
 * [Rising edge trigger](https://en.wikipedia.org/wiki/Signal_edge)
 * [Falling edge trigger](https://en.wikipedia.org/wiki/Signal_edge)
 
+### [sma.hh](sma.hh)
+
+The [simple moving average](https://en.wikipedia.org/wiki/Moving_average#Simple_moving_average) gives us the mean of the last N data points.
+
 ### [const.hh](const.hh)
 
 Some constants we need
diff --git a/sma.hh b/sma.hh
new file mode 100644
index 0000000..1067fe7
--- /dev/null
+++ b/sma.hh
@@ -0,0 +1,61 @@
+/*
+Simple moving average
+
+Copyright 2019 Ahmet Inan <inan@aicodix.de>
+*/
+
+#pragma once
+
+namespace DSP {
+
+template <typename TYPE, int NUM>
+class SMA1
+{
+	TYPE hist_inp[NUM];
+	TYPE hist_avg;
+	int hist_pos;
+public:
+	SMA1() : hist_avg(0), hist_pos(0)
+	{
+	}
+	TYPE abs_dev()
+	{
+		TYPE sum(abs(hist_inp[0] - hist_avg));
+		for (int i = 1; i < NUM; ++i)
+			sum += abs(hist_inp[i] - hist_avg);
+		return sum / NUM;
+	}
+	TYPE operator () (TYPE input)
+	{
+		hist_inp[hist_pos] = input;
+		if (++hist_pos >= NUM)
+			hist_pos = 0;
+		TYPE hist_sum(hist_inp[0]);
+		for (int i = 1; i < NUM; ++i)
+			hist_sum += hist_inp[i];
+		return hist_avg = hist_sum / NUM;
+	}
+};
+
+template <typename TYPE, int NUM>
+class SMA2
+{
+	TYPE hist_inp[NUM];
+	TYPE hist_sum;
+	int hist_pos;
+public:
+	SMA2() : hist_sum(0), hist_pos(0)
+	{
+	}
+	TYPE operator () (TYPE input)
+	{
+		hist_sum += input - hist_inp[hist_pos];
+		hist_inp[hist_pos] = input;
+		if (++hist_pos >= NUM)
+			hist_pos = 0;
+		return hist_sum / NUM;
+	}
+};
+
+}
+