Merge branch 'master' of https://github.com/firepixie/Adafruit_Learning_System_Guides

Author: firepixie

Circuit_Playground_Brake_Light/code.py

@@ -0,0 +1,60 @@
+import time
+import math
+from adafruit_circuitplayground import cp
+
+brightness = 0
+
+# List that holds the last 10 z-axis acceleration values read from the accelerometer.
+# Used for the n=10 moving average
+last10 = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+
+# List that holds the last 50 z-axis acceleration values read from the accelerometer.
+# Used for the n=50 moving average
+last50 = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+
+consecutive_triggers = 0
+cp.pixels.fill((255, 0, 0))
+
+light_on = False
+
+while True:
+    x, y, z = cp.acceleration
+
+    # moving average n=10, not super smooth, but it substantially lowers the amount of noise
+    last10.append(z)
+    last10.pop(0)
+    avg10 = sum(last10)/10
+
+    # moving average n=50, very smooth
+    last50.append(z)
+    last50.pop(0)
+    avg50 = sum(last50)/50
+
+    # If the difference between the moving average of the last 10 points and the moving average of
+    # the last 50 points is greater than 1 m/s^2, this is true
+    if avg10 - avg50 > 1:
+        if consecutive_triggers > 3: # Is true when avg10-avg50 > 1m/s^2 at least 3 times in a row
+            # Detects shake. Due to the very low shake threshold, this alone would have very low
+            # specificity. This was mitigated by having it only run when the acceleration
+            # difference is greater than 1 m/s^2 at least 3 times in a row.
+            if not cp.shake(shake_threshold=10):
+                # Set brightness to max, timestamp when it was set to max, and set light_on to true
+                cp.pixels.brightness = 1
+                start = time.monotonic()
+                light_on = True
+        consecutive_triggers += 1 # increase it whether or not the light is turned on
+
+    # light_on variable is for short circuiting. Not really necessary, just makes things run faster
+    elif not light_on or time.monotonic() - start > 0.4:
+        # Sine wave used for the color breathing effect.
+        # Max brightness can be adjusted with the coefficient.
+        cp.pixels.brightness = abs(math.sin(brightness)) * 0.5
+        brightness += 0.05
+        consecutive_triggers = 0
+        light_on = False
+
+    time.sleep(0.02)