Adding code for NeoPixel mini VU meter

Adding code the NeoPixel Mini VU Meter Learn Guide. Using a QT Py RP2040, PDM mic and strip of 16 neopixels

NeoPixel_Mini_VU_Meter/code.py

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+# SPDX-FileCopyrightText: 2022 Liz Clark for Adafruit Industries
+# SPDX-License-Identifier: MIT
+
+import time
+import array
+import math
+import board
+import audiobusio
+import simpleio
+import neopixel
+
+#  neopixel setup
+pixel_pin = board.A0
+
+pixel_num = 16
+
+pixels = neopixel.NeoPixel(pixel_pin, pixel_num, brightness=0.1, auto_write=False)
+
+#  function to average mic levels
+def mean(values):
+    return sum(values) / len(values)
+
+#  function to return mic level
+def normalized_rms(values):
+    minbuf = int(mean(values))
+    samples_sum = sum(
+        float(sample - minbuf) * (sample - minbuf)
+        for sample in values
+    )
+
+    return math.sqrt(samples_sum / len(values))
+
+#  mic setup
+mic = audiobusio.PDMIn(board.TX,
+                       board.A1, sample_rate=16000, bit_depth=16)
+samples = array.array('H', [0] * 160)
+
+#  variable to hold previous mic level
+last_input = 0
+
+#  neopixel colors
+GREEN = (0, 127, 0)
+RED = (127, 0, 0)
+YELLOW = (127, 127, 0)
+OFF = (0, 0, 0)
+
+#  array of colors for VU meter
+colors = [GREEN, GREEN, GREEN, GREEN, GREEN, GREEN, GREEN, GREEN,
+          GREEN, YELLOW, YELLOW, YELLOW, YELLOW, YELLOW, RED, RED]
+
+#  begin with pixels off
+pixels.fill(OFF)
+pixels.show()
+
+while True:
+    #  take in audio
+    mic.record(samples, len(samples))
+    #  magnitude holds the value of the mic level
+    magnitude = normalized_rms(samples)
+    #  uncomment to see the levels in the REPL
+    #  print((magnitude,))
+
+    #  mapping the volume range (125-500) to the 16 neopixels
+    #  volume range is optimized for music. you may want to adjust the range
+    #  based on the type of audio that you're trying to show
+    mapped_value = simpleio.map_range(magnitude, 125, 500, 0, 16)
+    #  converting the mapped range to an integer
+    input_val = int(mapped_value)
+
+    #  if the mic input has changed from the last input value...
+    if last_input != input_val:
+        for i in range(input_val):
+            #  if the level is lower...
+            if last_input > input_val:
+                for z in range(last_input):
+                    #  turn those pixels off
+                    pixels[z] = (OFF)
+            #  turn on pixels using the colors array
+            pixels[i] = (colors[i])
+            pixels.show()
+            #  update last_input
+            last_input = input_val
+
+    time.sleep(0.01)