Scrolling text on NEOPIXEL LEDs is quite a bit easier than on the previous LED panel, as it is part of the out-of-the-box functionality provided by the great and mighty adafruit.  I had the pleasure of working with the adafruit 8×8 neopixel array, as seen above.  These things are BRIGHT.  And unlike the previous LED panel, they don’t have any kind of cover or diffuser.

The result is that there is no dark color to contrast against, and the leds are so bright that they “bleed” into the surrounding space a little.  they also reflect off the glossy PCB.  The result is that at a distance, it can be a little hard to read the text on only an 8×8 panel.  A diffuser and a black mask around the pixels might help provide some contrast, and prevent the reflection problem.

Software:

The code was really simply.  The adafruit libraries take care of all the heavy lifting.  The one caveat is that I had to delete my Arduino Robot library because it caused some kind of error.

Some important but uncommented lines from the example are:

const uint16_t colors[] = {
matrix.Color(255, 0, 0), matrix.Color(0, 255, 0), matrix.Color(255, 255, 255) };

This makes an array of values to scroll text in.  Here it goes Red, Green, White.  You can add more or delete some but you may have to change loop iterator values later in the code.

matrix.print(F(“HI, RYAN.  THIS IS A NEOPIXEL BOARD”));
if(–x < -220) {

These lines control what gets printed to the matrix, and how much gets printed.  -220 can be made shorter to print only part of the message, and the string “HI RYAN, THIS IS A NEOPIXEL BOARD” can be changed to whatever you want.

Code dump:

// Adafruit_NeoMatrix example for single NeoPixel Shield.
// Scrolls ‘Howdy’ across the matrix in a portrait (vertical) orientation.

#include <Adafruit_GFX.h>
#include <Adafruit_NeoMatrix.h>
#include <Adafruit_NeoPixel.h>
#ifndef PSTR
#define PSTR // Make Arduino Due happy
#endif

#define PIN 6

// MATRIX DECLARATION:
// Parameter 1 = width of NeoPixel matrix
// Parameter 2 = height of matrix
// Parameter 3 = pin number (most are valid)
// Parameter 4 = matrix layout flags, add together as needed:
//   NEO_MATRIX_TOP, NEO_MATRIX_BOTTOM, NEO_MATRIX_LEFT, NEO_MATRIX_RIGHT:
//     Position of the FIRST LED in the matrix; pick two, e.g.
//     NEO_MATRIX_TOP + NEO_MATRIX_LEFT for the top-left corner.
//   NEO_MATRIX_ROWS, NEO_MATRIX_COLUMNS: LEDs are arranged in horizontal
//     rows or in vertical columns, respectively; pick one or the other.
//   NEO_MATRIX_PROGRESSIVE, NEO_MATRIX_ZIGZAG: all rows/columns proceed
//     in the same order, or alternate lines reverse direction; pick one.
//   See example below for these values in action.
// Parameter 5 = pixel type flags, add together as needed:
//   NEO_KHZ800  800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)
//   NEO_KHZ400  400 KHz (classic ‘v1’ (not v2) FLORA pixels, WS2811 drivers)
//   NEO_GRB     Pixels are wired for GRB bitstream (most NeoPixel products)
//   NEO_RGB     Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)

// Example for NeoPixel Shield.  In this application we’d like to use it
// as a 5×8 tall matrix, with the USB port positioned at the top of the
// Arduino.  When held that way, the first pixel is at the top right, and
// lines are arranged in columns, progressive order.  The shield uses
// 800 KHz (v2) pixels that expect GRB color data.
Adafruit_NeoMatrix matrix = Adafruit_NeoMatrix(8, 8, PIN,
NEO_MATRIX_TOP     + NEO_MATRIX_RIGHT +
NEO_MATRIX_COLUMNS + NEO_MATRIX_PROGRESSIVE,
NEO_GRB            + NEO_KHZ800);

const uint16_t colors[] = {
matrix.Color(255, 0, 0), matrix.Color(0, 255, 0), matrix.Color(255, 255, 255) };

void setup() {
matrix.begin();
matrix.setTextWrap(false);
matrix.setBrightness(40);
matrix.setTextColor(colors[0]);
}

int x    = matrix.width();
int pass = 0;

void loop() {
matrix.fillScreen(0);
matrix.setCursor(x, 0);
matrix.print(F(“HI, RYAN.  THIS IS A NEOPIXEL BOARD”));
if(–x < -220) {
x = matrix.width();
if(++pass >= 3) pass = 0;
matrix.setTextColor(colors[pass]);
}
matrix.show();
delay(100);
}

Hardware:

As usual, adafruit provides awesome information on hooking up the LEDs here.  But in case that is down or something, all you have to do to hook this up to an arduino is to hook up pin 6 to the DI pin through a 300-500 ohm resistor, and to supply power with a 5v 4A power supply.  the voltage can go below 5v, but not above 5v, as this will burn out the leds. Any amperage in excess of 4A is fine.

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