I have been using a library to control a LED Strip with buttons. My current code does not execute properly. It skips the if statement and just runs the code in a loop with no regard to the button and I'm uncertain why. I'm using an Arduino Uno with an LPD8806.

#include "LPD8806.h"
#include "SPI.h" // Comment out this line if using Trinket or Gemma
#ifdef __AVR_ATtiny85__
#include <avr/power.h>

int nLEDs = 160;

// Chose 2 pins for output; can be any valid output pins:
int dataPin  = 2;
int clockPin = 3;

// First parameter is the number of LEDs in the strand.  The LED strips
// are 32 LEDs per meter but you can extend or cut the strip.  Next two
// parameters are SPI data and clock pins:
LPD8806 strip = LPD8806(nLEDs, dataPin, clockPin);

int inPin = 4;
boolean lastState = LOW;//storage for last button state

void setup(){
   pinMode(inPin, INPUT);//this time we will set the pin as INPUT
   Serial.begin(9600);//initialize Serial connection
   #if defined(__AVR_ATtiny85__) && (F_CPU == 16000000L)
   clock_prescale_set(clock_div_1); // Enable 16 MHz on Trinket

   // Update the strip, to start they are all 'off'


void loop(){

   if (digitalRead(inPin) == HIGH && lastState == LOW){//if button has just       
   been pressed
   // Start up the LED strip
        theaterChase(strip.Color(127, 127, 127), 50); // White
    } else if(digitalRead(inPin) == LOW && lastState == HIGH){
        digitalWrite(dataPin, LOW);
        digitalWrite(clockPin, LOW);
    lastState = digitalRead(inPin);

    //Theatre-style crawling lights.
    void theaterChase(uint32_t c, uint8_t wait) {
         for (int j=0; j<10; j++) {  //do 10 cycles of chasing
              for (int q=0; q < 3; q++) {
                   for (int i=0; i < strip.numPixels(); i=i+3) {
                      strip.setPixelColor(i+q, c);    //turn every third pixel on


      for (int i=0; i < strip.numPixels(); i=i+3) {
      strip.setPixelColor(i+q, 0);        //turn every third pixel off
  • Do you have a pull-up or pull-down resistor on the input pin? See Switches tutorial.
    – Nick Gammon
    Commented Aug 13, 2015 at 3:36
  • Some of your comments overflow onto the next line of code...
    – TheDoctor
    Commented Aug 13, 2015 at 14:56
  • I think it doesn't work because you define the theatherChase() function inside loop(), where it should be before or after.
    – TheDoctor
    Commented Aug 13, 2015 at 14:58

1 Answer 1


If you have just connected a switch to the Arduino pin, like the image below, it will just return "random" undefined results:

Floating input on switch

There are various ways of avoiding this, including using a pull-down resistor to ensure that, if the switch is open, it will read LOW. For example:

Pull-down resistor

There are other possible techniques as discussed on this page.

One is to change:

   pinMode(inPin, INPUT);//this time we will set the pin as INPUT


   pinMode(inPin, INPUT_PULLUP);//this time we will set the pin as INPUT

Then wire the switch to ground, not +5 V. That way the pull-up resistor pulls the switch HIGH, and when you close the switch it is LOW.

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