Add support for downsampling encoder data

aeon/io/reader.py

@@ -11,7 +11,8 @@
 from dotmap import DotMap
 
 from aeon import util
-from aeon.io.api import chunk_key
+from aeon.io.api import chunk, chunk_key
+from aeon.io.api import aeon as aeon_time
 
 _SECONDS_PER_TICK = 32e-6
 _payloadtypes = {
@@ -185,6 +186,22 @@ class Encoder(Harp):
     def __init__(self, pattern):
         super().__init__(pattern, columns=["angle", "intensity"])
 
+    def read(self, file, downsample=True):
+        """Reads encoder data from the specified Harp binary file, and optionally downsamples
+        the frequency to 50Hz.
+        """
+        data = super().read(file)
+        if downsample is True:
+            # resample requires a DatetimeIndex so we convert early
+            data.index = aeon_time(data.index)
+
+            first_index = data.first_valid_index()
+            if first_index is not None:
+                # since data is absolute angular position we decimate by taking first of each bin
+                chunk_origin = chunk(first_index)
+                data = data.resample('20ms', origin=chunk_origin).first()
+        return data
+
 
 class Position(Harp):
     """Extract 2D position tracking data for a specific camera.