The Arduino code presented below works equally well on all versions of GEMMA: v2 and M0. But if you have an M0 board, consider using the CircuitPython code on the next page of this guide, no Arduino IDE required! Click to Download the NeoPixel Library
Installing Arduino libraries is a frequent stumbling block. If this is your first time, or simply needing a refresher, please read the All About Arduino Libraries tutorial.
If the library is correctly installed (and the Arduino IDE is restarted), you should be able to navigate through the “File” rollover menus as follows:
File→Sketchbook→Libraries→Adafruit_NeoPixel→strandtest
// SPDX-FileCopyrightText: 2013 Phil Burgess for Adafruit Industries
//
// SPDX-License-Identifier: BSD-3-Clause
/*
LED VU meter for Arduino and Adafruit NeoPixel LEDs.
Hardware requirements:
- Most Arduino or Arduino-compatible boards (ATmega 328P or better).
- Adafruit Electret Microphone Amplifier (ID: 1063)
- Adafruit Flora RGB Smart Pixels (ID: 1260)
OR
- Adafruit NeoPixel Digital LED strip (ID: 1138)
- Optional: battery for portable use (else power through USB or adapter)
Software requirements:
- Adafruit NeoPixel library
Connections:
- 3.3V to mic amp +
- GND to mic amp -
- Analog pin to microphone output (configurable below)
- Digital pin to LED data input (configurable below)
See notes in setup() regarding 5V vs. 3.3V boards - there may be an
extra connection to make and one line of code to enable or disable.
Written by Adafruit Industries. Distributed under the BSD license.
This paragraph must be included in any redistribution.
fscale function:
Floating Point Autoscale Function V0.1
Written by Paul Badger 2007
Modified from code by Greg Shakar
*/
#include <Adafruit_NeoPixel.h>
#include <math.h>
#define N_PIXELS 16 // Number of pixels in strand
#define MIC_PIN A1 // Microphone is attached to this analog pin
#define LED_PIN 1 // NeoPixel LED strand is connected to this pin
#define SAMPLE_WINDOW 10 // Sample window for average level
#define PEAK_HANG 24 //Time of pause before peak dot falls
#define PEAK_FALL 4 //Rate of falling peak dot
#define INPUT_FLOOR 10 //Lower range of analogRead input
#define INPUT_CEILING 300 //Max range of analogRead input, the lower the value the more sensitive (1023 = max)
byte peak = 16; // Peak level of column; used for falling dots
unsigned int sample;
byte dotCount = 0; //Frame counter for peak dot
byte dotHangCount = 0; //Frame counter for holding peak dot
Adafruit_NeoPixel strip = Adafruit_NeoPixel(N_PIXELS, LED_PIN, NEO_GRB + NEO_KHZ800);
void setup()
{
// This is only needed on 5V Arduinos (Uno, Leonardo, etc.).
// Connect 3.3V to mic AND TO AREF ON ARDUINO and enable this
// line. Audio samples are 'cleaner' at 3.3V.
// COMMENT OUT THIS LINE FOR 3.3V ARDUINOS (FLORA, ETC.):
// analogReference(EXTERNAL);
// Serial.begin(9600);
strip.begin();
strip.show(); // Initialize all pixels to 'off'
}
void loop()
{
unsigned long startMillis= millis(); // Start of sample window
float peakToPeak = 0; // peak-to-peak level
unsigned int signalMax = 0;
unsigned int signalMin = 1023;
unsigned int c, y;
// collect data for length of sample window (in mS)
while (millis() - startMillis < SAMPLE_WINDOW)
{
sample = analogRead(MIC_PIN);
if (sample < 1024) // toss out spurious readings
{
if (sample > signalMax)
{
signalMax = sample; // save just the max levels
}
else if (sample < signalMin)
{
signalMin = sample; // save just the min levels
}
}
}
peakToPeak = signalMax - signalMin; // max - min = peak-peak amplitude
// Serial.println(peakToPeak);
//Fill the strip with rainbow gradient
for (int i=0;i<=strip.numPixels()-1;i++){
strip.setPixelColor(i,Wheel(map(i,0,strip.numPixels()-1,30,150)));
}
//Scale the input logarithmically instead of linearly
c = fscale(INPUT_FLOOR, INPUT_CEILING, strip.numPixels(), 0, peakToPeak, 2);
if(c < peak) {
peak = c; // Keep dot on top
dotHangCount = 0; // make the dot hang before falling
}
if (c <= strip.numPixels()) { // Fill partial column with off pixels
drawLine(strip.numPixels(), strip.numPixels()-c, strip.Color(0, 0, 0));
}
// Set the peak dot to match the rainbow gradient
y = strip.numPixels() - peak;
strip.setPixelColor(y-1,Wheel(map(y,0,strip.numPixels()-1,30,150)));
strip.show();
// Frame based peak dot animation
if(dotHangCount > PEAK_HANG) { //Peak pause length
if(++dotCount >= PEAK_FALL) { //Fall rate
peak++;
dotCount = 0;
}
}
else {
dotHangCount++;
}
}
//Used to draw a line between two points of a given color
void drawLine(uint8_t from, uint8_t to, uint32_t c) {
uint8_t fromTemp;
if (from > to) {
fromTemp = from;
from = to;
to = fromTemp;
}
for(int i=from; i<=to; i++){
strip.setPixelColor(i, c);
}
}
float fscale( float originalMin, float originalMax, float newBegin, float
newEnd, float inputValue, float curve){
float OriginalRange = 0;
float NewRange = 0;
float zeroRefCurVal = 0;
float normalizedCurVal = 0;
float rangedValue = 0;
boolean invFlag = 0;
// condition curve parameter
// limit range
if (curve > 10) curve = 10;
if (curve < -10) curve = -10;
curve = (curve * -.1) ; // - invert and scale - this seems more intuitive - postive numbers give more weight to high end on output
curve = pow(10, curve); // convert linear scale into lograthimic exponent for other pow function
/*
Serial.println(curve * 100, DEC); // multply by 100 to preserve resolution
Serial.println();
*/
// Check for out of range inputValues
if (inputValue < originalMin) {
inputValue = originalMin;
}
if (inputValue > originalMax) {
inputValue = originalMax;
}
// Zero Refference the values
OriginalRange = originalMax - originalMin;
if (newEnd > newBegin){
NewRange = newEnd - newBegin;
}
else
{
NewRange = newBegin - newEnd;
invFlag = 1;
}
zeroRefCurVal = inputValue - originalMin;
normalizedCurVal = zeroRefCurVal / OriginalRange; // normalize to 0 - 1 float
// Check for originalMin > originalMax - the math for all other cases i.e. negative numbers seems to work out fine
if (originalMin > originalMax ) {
return 0;
}
if (invFlag == 0){
rangedValue = (pow(normalizedCurVal, curve) * NewRange) + newBegin;
}
else // invert the ranges
{
rangedValue = newBegin - (pow(normalizedCurVal, curve) * NewRange);
}
return rangedValue;
}
// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
if(WheelPos < 85) {
return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
}
else if(WheelPos < 170) {
WheelPos -= 85;
return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
}
else {
WheelPos -= 170;
return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);
}
}
From the Tools→Board menu, select the device you are using:
- Adafruit Gemma M0
- Adafruit Gemma 8 MHz
Connect the USB cable between the computer and your device. The original Gemma (8 MHz) need the reset button pressed on the board, then click the upload button (right arrow icon) in the Arduino IDE. You do not need to press the reset on the newer Gemma M0.
When the battery is connected, you should get a light show from the LEDs. All your pixels working? Great! You can take apart this prototype and get ready to put the pixels in the collar. Refer to the NeoPixel Uberguide for more info.
Page last edited January 22, 2025
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