From c2be6b7a7399af4a5b0c8d6d351bc2171ad41464 Mon Sep 17 00:00:00 2001
From: schneider <schneider@blinkenlichts.net>
Date: Fri, 10 Apr 2020 19:30:14 +0200
Subject: [PATCH] fix(spo2): Use IIR filter for offset removal
---
preload/apps/spo2/__init__.py | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/preload/apps/spo2/__init__.py b/preload/apps/spo2/__init__.py
index cf565d8e0..dbe9b83c4 100644
--- a/preload/apps/spo2/__init__.py
+++ b/preload/apps/spo2/__init__.py
@@ -23,6 +23,7 @@ class SPO2:
self.last_sample = 0.0
self.filtered_value = 0.0
self.source = "Red"
+ self.average = 0
def open(self):
def callback(datasets):
@@ -45,7 +46,9 @@ class SPO2:
while buttons.read(buttons.BOTTOM_RIGHT): pass
def update_history(self, datasets):
+ alpha = 0.995
for val in datasets:
+ """
if self.source == "Red":
self.avg[self.avg_pos] = val.red
else:
@@ -63,6 +66,17 @@ class SPO2:
)
self.last_sample = avg_data
self.history.append(self.filtered_value)
+ """
+
+ #print("%d,%d" % (val.red, val.infrared))
+ if self.source == "Red":
+ d = val.red
+ else:
+ d = val.infrared
+
+ self.average = alpha * self.average + (1 - alpha) * d
+ d -= self.average
+ self.history.append(d)
# trim old elements
self.history = self.history[-self.HISTORY_MAX :]
--
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