If this is your first time using Trinket or Gemma, work through the guides first:
You need to customize some settings in the Arduino IDE. Once you have it up and running (test the 'blink' sketch), then download and install the NeoPixel library:
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
You’ll need to change one line in this code. If using Trinket, change line #4 to:
#define PIN 4
#define PIN 1
If that’s working, you can then copy and paste this Larson scanner code into a new sketch. Change N_LEDS to match the number of LEDs in your strip, and if using Gemma change PIN to 1. Upload and get ready to be a Cylon!
#include <Adafruit_NeoPixel.h>
#define N_LEDS 22
#define PIN 4
Adafruit_NeoPixel strip = Adafruit_NeoPixel(N_LEDS, PIN, NEO_GRB + NEO_KHZ800);
void setup() {
strip.begin();
}
int pos = 0, dir = 1; // Position, direction of "eye"
void loop() {
int j;
// Draw 5 pixels centered on pos. setPixelColor() will clip any
// pixels off the ends of the strip, we don't need to watch for that.
strip.setPixelColor(pos - 2, 0x100000); // Dark red
strip.setPixelColor(pos - 1, 0x800000); // Medium red
strip.setPixelColor(pos , 0xFF3000); // Center pixel is brightest
strip.setPixelColor(pos + 1, 0x800000); // Medium red
strip.setPixelColor(pos + 2, 0x100000); // Dark red
strip.show();
delay(30);
// Rather than being sneaky and erasing just the tail pixel,
// it's easier to erase it all and draw a new one next time.
for(j=-2; j<= 2; j++) strip.setPixelColor(pos+j, 0);
// Bounce off ends of strip
pos += dir;
if(pos < 0) {
pos = 1;
dir = -dir;
} else if(pos >= strip.numPixels()) {
pos = strip.numPixels() - 2;
dir = -dir;
}
}
This code works equally well on an Adafruit Hallowing board with a NeoPixel strip plugged into the NEOPIX port. Just change the number on the “N_LEDS” line to match your strip length. No need to change PIN, the default (4) already matches the NeoPixel connector on this board.
