Commit 8f78143e authored by fleur's avatar fleur
Browse files

added filter doc and cleaned up a bit

parent dc83ef34
......@@ -51,12 +51,13 @@ last_sample_count = 1
leds.dim_top(1)
COLORS = [((23 + (15 * i)) % 360, 1.0, 1.0) for i in range(11)]
# variables for high-pass filter
# note: corresponds to 1st order hpf with -3dB at ~18.7Hz
# general formula: f(-3dB)=-(sample_rate/tau)*ln(1-betadash)
moving_average = 0
alpha = 2
beta = 3
betadash = beta/(alpha+beta)
def update_history(datasets):
global history, moving_average, alpha, beta, last_sample_count
......@@ -64,7 +65,8 @@ def update_history(datasets):
for val in datasets:
if current_mode == MODE_FINGER:
history.append(val - moving_average)
moving_average = (alpha * moving_average + beta * val) / (alpha + beta)
moving_average += betadash*(val-moving_average)
# identical to: moving_average = (alpha * moving_average + beta * val) / (alpha + beta)
else:
history.append(val)
......
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