Metro MO and LED strips


I have had some successes diving into this project. I am struggling with the code. Not understanding the error messages and what to do next. Any advice would be greatly appreciated.

Ultimately this is going to be part of a sound-activated LED strip module I can replicate and place around my drumset :slight_smile:


Hi! What is your question? Can you post your code and describe the errors?

I've copied code containing sections that the author starts with an "#".

An "//" would be used to comment out a section. Is it possible the author made an intentional error to force the user to do something with the code?


Where did you get your code from? What is the code?

# is usually used to prefix precompiler stuff like #include or #define. It probably has nothing to do with forcing the user to do something with the code... rather, it is necessary for the code to work.

Please post your code and the error you are getting, if there is one.

Thanks for your response. I seem to have figured it out. My LED strips are reacting to mic input. To take my project to the next stage, I need to learn about the coding. I will start by analyzing the code below. I know very few of the commands listed so any advice/interpretation on the code would be appreciated.


/* LED "Color Organ" for Adafruit Trinket and NeoPixel LEDs.

Hardware requirements:
 - Adafruit Trinket or Gemma mini microcontroller (ATTiny85).
 - Adafruit Electret Microphone Amplifier (ID: 1063)
 - Several Neopixels, you can mix and match
   o Adafruit Flora RGB Smart Pixels (ID: 1260)
   o Adafruit NeoPixel Digital LED strip (ID: 1138)
   o Adafruit Neopixel Ring (ID: 1463)

Software requirements:
 - Adafruit NeoPixel library

 - 5 V to mic amp +
 - GND to mic amp -
 - Analog pinto microphone output (configurable below)
 - Digital pin to LED data input (configurable below)

Written by Adafruit Industries.  Distributed under the BSD license.
This paragraph must be included in any redistribution.
#include <Adafruit_NeoPixel.h>

#define N_PIXELS  60  // Number of pixels you are using
#define MIC_PIN   A0  // Microphone is attached to Trinket GPIO #2/Gemma D2 (A1)
#define LED_PIN    A1  // NeoPixel LED strand is connected to GPIO #0 / D0
#define DC_OFFSET  0  // DC offset in mic signal - if unusure, leave 0
#define NOISE     125  // Noise/hum/interference in mic signal
#define SAMPLES   60  // Length of buffer for dynamic level adjustment
#define TOP       (N_PIXELS +1) // Allow dot to go slightly off scale
// Comment out the next line if you do not want brightness control or have a Gemma
#define POT_PIN    3  // if defined, a potentiometer is on GPIO #3 (A3, Trinket only) 

  peak      = 0,      // Used for falling dot
  dotCount  = 0,      // Frame counter for delaying dot-falling speed
  volCount  = 0;      // Frame counter for storing past volume data
  vol[SAMPLES],       // Collection of prior volume samples
  lvl       = 10,     // Current "dampened" audio level
  minLvlAvg = 0,      // For dynamic adjustment of graph low & high
  maxLvlAvg = 512;

Adafruit_NeoPixel  strip = Adafruit_NeoPixel(N_PIXELS, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  //memset(vol, 0, sizeof(vol));
  memset(vol,0,sizeof(int)*SAMPLES);//Thanks Neil!
void loop() {
  uint8_t  i;
  uint16_t minLvl, maxLvl;
  int      n, height;
  n   = analogRead(MIC_PIN);                 // Raw reading from mic 
  n   = abs(n - 512 - DC_OFFSET);            // Center on zero
  n   = (n <= NOISE) ? 0 : (n - NOISE);      // Remove noise/hum
  lvl = ((lvl * 7) + n) >> 3;    // "Dampened" reading (else looks twitchy)
  // Calculate bar height based on dynamic min/max levels (fixed point):
  height = TOP * (lvl - minLvlAvg) / (long)(maxLvlAvg - minLvlAvg);

  if(height < 0L)       height = 0;      // Clip output
  else if(height > TOP) height = TOP;
  if(height > peak)     peak   = height; // Keep 'peak' dot at top

// if POT_PIN is defined, we have a potentiometer on GPIO #3 on a Trinket 
//    (Gemma doesn't have this pin)
  uint8_t bright = 255;   
#ifdef POT_PIN            
   bright = analogRead(POT_PIN);  // Read pin (0-255) (adjust potentiometer 
                                  //   to give 0 to Vcc volts
  strip.setBrightness(bright);    // Set LED brightness (if POT_PIN at top
                                  //  define commented out, will be full)
  // Color pixels based on rainbow gradient
  for(i=0; i<N_PIXELS; i++) {  
    if(i >= height)               
       strip.setPixelColor(i,   0,   0, 0);
    }; // Update strip

  vol[volCount] = n;                      // Save sample for dynamic leveling
  if(++volCount >= SAMPLES) volCount = 0; // Advance/rollover sample counter

  // Get volume range of prior frames
  minLvl = maxLvl = vol[0];
  for(i=1; i<SAMPLES; i++) {
    if(vol[i] < minLvl)      minLvl = vol[i];
    else if(vol[i] > maxLvl) maxLvl = vol[i];
  // minLvl and maxLvl indicate the volume range over prior frames, used
  // for vertically scaling the output graph (so it looks interesting
  // regardless of volume level).  If they're too close together though
  // (e.g. at very low volume levels) the graph becomes super coarse
  // and 'jumpy' keep some minimum distance between them (this
  // also lets the graph go to zero when no sound is playing):
  if((maxLvl - minLvl) < TOP) maxLvl = minLvl + TOP;
  minLvlAvg = (minLvlAvg * 63 + minLvl) >> 6; // Dampen min/max levels
  maxLvlAvg = (maxLvlAvg * 63 + maxLvl) >> 6; // (fake rolling average)

// Input a value 0 to 255 to get a color value.
// The colors 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);

I'd consider your code to be too advanced for a beginner... if you don't know what's going on, then I'd suggest for you to start with more basic projects with tutorials that will actually teach you what is going on. I'll be happy to answer specific questions or problems about your code (not what your entire sketch does), but you must do your own research.