Software Setup

If this is your first time using Pro Trinket, take a look at Introducting Pro Trinket to get a guided tour.   

FastLED Library

You will also need to install the FastLED library in Arduino (Sketch > Include Library > Manage Libraries...)

Libraries? Why? What's a Library?

In a nutshell, Arduino libraries have a lot of pre-written functions that make your DotStar LEDs easy to command.  You can do fancy stuff without being a code guru. Yay Libraries!

FastLED is a fast, efficient, easy-to-use Arduino library for programming addressable LED strips and pixels.  It has a lot of features to get your animations up and running fast -- and it has a lot of code samples available if you're just learning to code.

All about Arduino Libraries will tell you everything you ever wanted to know about libraries, including more detailed installation instructions.

Once your curiosity is satiated and your library is installed, copy and paste the code into your Arduino window.

Go to your Tools menu and select "Pro Trinket 5V USB" from the list of boards.  Plug your Pro Trinket into your computer via the onboard USB port.  Press the "reset" button on your Pro Trinket and wait for the blinky red light, then click the upload button in Arduino.

//Code includes samples written by Mark Kriegsman and Andrew Tuline.  Thanks so much for all your help guys!

#include <FastLED.h>

#define LED_PIN 4
#define CLOCK_PIN 3
#define BUTTON_PIN 5 

#define NUM_LEDS 38       // Change to reflect the number of LEDs you have

CRGB leds[NUM_LEDS];      //naming our LED array

byte prevKeyState = HIGH;        

int ledMode = 0;  //FIRST ACTIVE MODE

CRGBPalette16 currentPalette;
TBlendType    currentBlending;

// MODE VARIABLES -- Change these numbers to create new interesting modes

int BRIGHTNESS = 255;    //0-255.  Lower number saves battery life, higher number is screamingly bright
int SATURATION = 255;    //0 is white (no color) and 255 is fully saturated with color
int HUE = 0;             //0-255, around the color wheel
int STEPS = 4;           //Wider or narrower bands of color
int SPEEDO = 10;         //The speed of the animation


#define qsubd(x, b)  ((x>b)?wavebright:0)                   // Digital unsigned subtraction macro. if result <0, then => 0. Otherwise, take on fixed value.
#define qsuba(x, b)  ((x>b)?x-b:0)                          // Analog Unsigned subtraction macro. if result <0, then => 0

// SINWAVE VARIABLES -- change these numbers to modify Sinwave mode
uint8_t wavebright = 255;                                     // You can change the brightness of the waves/bars rolling across the screen.
uint8_t thishue = 30;                                          // You can change the starting hue value for the first wave.
uint8_t thisrot = 1;                                          // You can change how quickly the hue rotates for this wave. 0= color stays the same
uint8_t allsat = 255;                                         // I like 'em fully saturated with colour.
bool thisdir = 0;                                             // You can change direction.
int8_t thisspeed = 4;                                         // You can change the speed, and use negative values.
uint8_t allfreq = 25;                                         // You can change the frequency, thus overall width of bars.
int thisphase = 0;                                            // Phase change value gets calculated.
uint8_t thiscutoff = 192;                                     // You can change the cutoff value to display this wave. Lower value = longer wave.
int loopdelay = 4;                                           // You can change the delay. Also you can change the allspeed variable above. 
uint8_t bgclr = 0;                                            // A rotating background colour.
uint8_t bgbright = 55;                                        // Background color brightness


uint8_t colour;                                               // Ripple colour is randomized.
int center = 0;                                               // Center of the current ripple.
int step = -1;                                                // -1 is the initializing step.
uint8_t myfade = 255;                                         // Starting brightness.
#define maxsteps 16                                           // Case statement wouldn't allow a variable.

void setup()  
  delay( 2000 ); // power-up safety delay

  FastLED.addLeds<DOTSTAR, LED_PIN, CLOCK_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection( TypicalLEDStrip );
  FastLED.setBrightness(  BRIGHTNESS );
  currentBlending = LINEARBLEND;

#define NUM_MODES 3
//------------------MAIN LOOP------------------
void loop() {
    switch (ledMode) {
       case 0: BRIGHTNESS = 255; Rainbow(); break;              //Rainbow -- Change STEPS and SPEED to modify
       case 1: sinwave_1(); break;            //Sin Wave -- Change sinwave variables to modify
       case 2: ripple(); break;               //Ripple -- Change 
       case 3: BRIGHTNESS=0; Solid(); break;  //all off -- change BRIGHTNESS to 1-255 for a solid color

 // button management section
        byte currKeyState = digitalRead(BUTTON_PIN);
        if ((prevKeyState == LOW) && (currKeyState == HIGH)) {
        prevKeyState = currKeyState;

// SOLID COLOR -------------------------------------
void Solid()

void sinwave_1() {

void one_sin() {                                                                // This is the heart of this program. Sure is short.
  if (thisdir == 0) thisphase+=thisspeed; else thisphase-=thisspeed;            // You can change direction and speed individually.
    thishue = thishue + thisrot;                                                // Hue rotation is fun for thiswave.
  for (int k=0; k<NUM_LEDS; k++) {
    int thisbright = qsubd(cubicwave8((k*allfreq)+thisphase), thiscutoff);      // qsub sets a minimum value called thiscutoff. If < thiscutoff, then bright = 0. Otherwise, bright = 128 (as defined in qsub)..
    leds[k] = CHSV(bgclr, 255, bgbright);
    leds[k] += CHSV(thishue, allsat, thisbright);                               // Assigning hues and brightness to the led array.
} // one_sin()

// RAINBOW --------------------------------------------------
void Rainbow()
  FastLED.setBrightness(  BRIGHTNESS );
  currentPalette = RainbowColors_p;
  static uint8_t startIndex = 0;
  startIndex = startIndex + 1; 

  FillLEDsFromPaletteColors( startIndex);;

void FillLEDsFromPaletteColors( uint8_t colorIndex)
  for( int i = 0; i < NUM_LEDS; i++) {
    leds[i] = ColorFromPalette( currentPalette, colorIndex, BRIGHTNESS, currentBlending);
    colorIndex += STEPS;

//RIPPLE --------------------------------------------------------------------------------
void ripple() {
  HUE = 140;HUE++; 
    if (HUE > 220) {HUE = 140;}   // constrain BG hue to blues and purples
  for (int i = 0; i < NUM_LEDS; i++) leds[i] = CHSV(HUE++, 255, 50);  // Rotate background colour.

  switch (step) {

    case -1:                                                          // Initialize ripple variables.
      center = random(NUM_LEDS);
      colour = random16(0,256);
      step = 0;

    case 0:
      leds[center] = CHSV(colour, 255, 255);                          // Display the first pixel of the ripple.
      step ++;

    case maxsteps:                                                    // At the end of the ripples.
      step = -1;

    default:                                                          // Middle of the ripples.
        leds[wrap(center + step)] += CHSV(colour, 255, myfade/step*2);   // Display the next pixels in the range for one side.
        leds[wrap(center - step)] += CHSV(colour, 255, myfade/step*2);   // Display the next pixels in the range for the other side.
        step ++;                                                      // Next step.
  } // switch step
} // ripple()
int wrap(int step) {
  if(step < 0) return NUM_LEDS + step;
  if(step > NUM_LEDS - 1) return step - NUM_LEDS;
  return step;
} // wrap()

// called when button is pressed
void shortKeyPress() {
    if (ledMode > NUM_MODES){
    ledMode=0; }

// called when key goes from pressed to not pressed
void keyRelease() {
    Serial.println("key release");

If you encounter trouble…

Any time you hit a roadblock with a DotStar project, we’ll usually ask that you start with the “strandtest” example from our own Adafruit_DotStar library. This helps us narrow down whether it’s a hardware or software issue. The library is installed similarly to FastLED or any other in Arduino (Sketch > Include Library > Manage Libraries...)

You’ll find the strandtest example under File→Sketchbook→Libraries→Adafruit_DotStar→strandtest

If strandtest fails to run, this suggests a hardware issue…for example, connecting to the wrong Trinket pin.

If you’re new to Arduino programming and LEDs, we usually suggest starting with the Adafruit_DotStar library…it’s pretty basic, the strip declaration is more conventional, and we can stay on top of keeping it compatible with our own products and the most mainstream Arduino boards.

As FastLED is a more “bleeding edge” third-party library, we can’t always guarantee compatibility across versions or with specific boards. You can find help through their community on Google+. This is potent stuff, written by people with a deep appreciation for LED art, and we wanted to showcase it.

This guide was first published on Jan 23, 2015. It was last updated on Jan 23, 2015.

This page (The Code) was last updated on Apr 17, 2021.

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