The Adafruit Circuit Playground Express comes equipped with an onboard microphone that is capable of sensing both amplitude and frequency. This tutorial will walk through a quick sketch using CircuitPython to turn the lights on the board into a mic activated VU-meter-like display! The microphone is located on the lower right side of the board, marked with an ear.
In this program, samples are taken from the microphone and then the sound level is averaged out to create a smoother looking display on the NeoPixels. Try playing around with the settings to change the way that the lights behave.
- CURVE- Change this to adjust the exponential scaling
- PEAK_COLOR- This changes the color of the top NeoPixel
- NUM_PIXELS- This sets the number of pixels, if you attached a strip you would set the number here.
- NUM_SAMPPLES- This sets the number of samples to read at once, reduce this to make the display jumpier
- input_floor- Normally a short sample is taken at startup that sets the low end of the sound range. If this isn’t working or you have too much noise still you can set it manually. You can check your microphone readings by adding print(magnitude) to the loop.
# The MIT License (MIT)0 # # Copyright (c) 2017 Dan Halbert for Adafruit Industries # Copyright (c) 2017 Kattni Rembor, Tony DiCola for Adafruit Industries # # Permission is hereby granted, free of charge, to any person obtaining a copy # of this software and associated documentation files (the "Software"), to deal # in the Software without restriction, including without limitation the rights # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell # copies of the Software, and to permit persons to whom the Software is # furnished to do so, subject to the following conditions: # # The above copyright notice and this permission notice shall be included in # all copies or substantial portions of the Software. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN # THE SOFTWARE. import array import math import audiobusio import board import neopixel # Exponential scaling factor. # Should probably be in range -10 .. 10 to be reasonable. CURVE = 2 SCALE_EXPONENT = math.pow(10, CURVE * -0.1) PEAK_COLOR = (100, 0, 255) NUM_PIXELS = 10 # Number of samples to read at once. NUM_SAMPLES = 160 # Restrict value to be between floor and ceiling. def constrain(value, floor, ceiling): return max(floor, min(value, ceiling)) # Scale input_value between output_min and output_max, exponentially. def log_scale(input_value, input_min, input_max, output_min, output_max): normalized_input_value = (input_value - input_min) / \ (input_max - input_min) return output_min + \ math.pow(normalized_input_value, SCALE_EXPONENT) \ * (output_max - output_min) # Remove DC bias before computing RMS. 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)) def mean(values): return sum(values) / len(values) def volume_color(volume): return 200, volume * (255 // NUM_PIXELS), 0 # Main program # Set up NeoPixels and turn them all off. pixels = neopixel.NeoPixel(board.NEOPIXEL, NUM_PIXELS, brightness=0.1, auto_write=False) pixels.fill(0) pixels.show() """ # For CircuitPython 2.x: mic = audiobusio.PDMIn(board.MICROPHONE_CLOCK, board.MICROPHONE_DATA, frequency=16000, bit_depth=16) # For Circuitpython 3.0 and up, "frequency" is now called "sample_rate". # Comment the lines above and uncomment the lines below. """ mic = audiobusio.PDMIn(board.MICROPHONE_CLOCK, board.MICROPHONE_DATA, sample_rate=16000, bit_depth=16) # Record an initial sample to calibrate. Assume it's quiet when we start. samples = array.array('H',  * NUM_SAMPLES) mic.record(samples, len(samples)) # Set lowest level to expect, plus a little. input_floor = normalized_rms(samples) + 10 # OR: used a fixed floor # input_floor = 50 # You might want to print the input_floor to help adjust other values. # print(input_floor) # Corresponds to sensitivity: lower means more pixels light up with lower sound # Adjust this as you see fit. input_ceiling = input_floor + 500 peak = 0 while True: mic.record(samples, len(samples)) magnitude = normalized_rms(samples) # You might want to print this to see the values. # print(magnitude) # Compute scaled logarithmic reading in the range 0 to NUM_PIXELS c = log_scale(constrain(magnitude, input_floor, input_ceiling), input_floor, input_ceiling, 0, NUM_PIXELS) # Light up pixels that are below the scaled and interpolated magnitude. pixels.fill(0) for i in range(NUM_PIXELS): if i < c: pixels[i] = volume_color(i) # Light up the peak pixel and animate it slowly dropping. if c >= peak: peak = min(c, NUM_PIXELS - 1) elif peak > 0: peak = peak - 1 if peak > 0: pixels[int(peak)] = PEAK_COLOR pixels.show()
There are a lot of other possible projects you can do with the Adafruit Circuit Playground Express! Check out our Circuit Playground Tutorials for more great info on how to unlock the potential of this great platform!