diff --git a/INSTALL b/INSTALL
index d33d73f..a303fc6 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,6 +1,8 @@
 Das Programm kann direkt gestartet werden. Eine Installation ist nicht
 erforderlich. Die unten angegebenen Abhängigkeiten müssen erfüllt sein.
 
+Python muß mindestens Version 3.10 sein.
+
 apt-get install python3-cairo python3-gi python3-gi-cairo gir1.2-rsvg-2.0 \
     python-serial python3-nmea2 python3-smbus2 python3-bme280
 
diff --git a/nmea2000/mavg.py b/nmea2000/mavg.py
index 604be4e..9f5327f 100644
--- a/nmea2000/mavg.py
+++ b/nmea2000/mavg.py
@@ -1,25 +1,56 @@
-'''
+"""
 Moving Average
+returns a float so no integer rounding applied
 
-Sortierung einer Liste nach Alter? FIFO?
-
-'''
-
-import time
+"""
 
 class mAvg():
 
-    def __init__(self, interval):
-        self.interval = interval
-        self.avg = None
-        self.data = []
+    def __init__(self, size):
+        self.size = size
+        self.data = [0] * size
+        self.nval = 0
+        self.sum = 0
+        self.next = 0
 
     def addVal(self, value):
-        self.data.append((time.time(), value))
+        # add a new value und return new current avg
+        if self.nval < self.size:
+            # list is not filled
+            self.nval += 1
+            self.sum += value
+        else:
+            # list is filled
+            self.sum = self.sum - self.data[self.next] - value
+        self.data.[self.next] = value
+        self.next += 1
+        # if end of list reached, start over from beginning
+        if self.next = self.size:
+            self.next = 0
+        return self.sum / self.nval
 
-    def setInterval(self, interval):
-        pass
+    def getAvg(self, points=None):
+        if self.nval == 0:
+            return None
+        # get avg of all collected data
+        if not points:
+            return self.sum / self.nval
+        # get avg of subset
+        if points > self.nval:
+            return None
+        sum = 0
+        i = self.next
+        p = points
+        while p > 0:
+            p -= 1
+            if i == 0:
+                i = self.size - 1
+            else:
+                i -= 1
+            sum += self.data[i]
+        return sum / points
 
-    def getAvg(self):
-        return self.avg
-        
\ No newline at end of file
+    def reset(self):
+        self.nval = 0
+        self.next = 0
+        self.sum = 0