#include <Adafruit_NeoMatrix.h> // https://github.com/adafruit/Adafruit_NeoMatrix

// offload arrays from RAM to PROGMEM
// #include <avr/pgmspace.h>  // https://github.com/Synapseware/avr/blob/master/include/avr/pgmspace.h

#define LED_PIN 6 // Data pin
#define DISPLAY_WIDTH 56 // 64 is too much for Uno/Nano
#define DISPLAY_HEIGHT 8
#define BRIGHTNESS 255
byte delayMS = 20;

Adafruit_NeoMatrix matrix = Adafruit_NeoMatrix (
                              DISPLAY_WIDTH, DISPLAY_HEIGHT, LED_PIN,
                              NEO_MATRIX_TOP + // NEO_MATRIX_BOTTOM
                              NEO_MATRIX_LEFT + // NEO_MATRIX_RIGHT
                              NEO_MATRIX_ROWS + // NEO_MATRIX_COLUMNS
                              NEO_MATRIX_PROGRESSIVE, // NEO_MATRIX_ZIGZAG,
                              NEO_GRB + // NEO_RGB
                              NEO_KHZ800 // NEO_KHZ400
                            );
                            
int scrollWidth = matrix.width();

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

// char sometext[] = "Never gonna give you up."; // use with matrix.print(sometext);
const char sometext[] PROGMEM = {"Never Gonna Give You Up"}; // 144 pixels
int textlength = sizeof(sometext);
int scrolloff = textlength * 6; // each character is 5 pixels plus one kern pixel

void setup() {
  // Serial.begin(115200);
  matrix.begin(); // Initialize the display object
  matrix.setTextWrap(false);
  matrix.setBrightness(BRIGHTNESS);
  matrix.setTextColor(colors[1]); // white
}

void loop() {
  scrollText();
}

void scrollText() {
  matrix.fillScreen(0);    //Turn off all the LEDs
  matrix.setCursor(scroll, 0); // start displaying Neopixels at the right edge
  // matrix.print(sometext); // use with array of characters - no loop needed
  for (int i = 0; i < textlength; i++) { // read all characters...
    matrix.write(pgm_read_byte(sometext + i)); // ...from PROGMEM into buffer
  }
  if ( --scrollWidth < -scrolloff ) { // count from (size of matrix) to (negative)textlength
    scrollWidth = matrix.width(); // re-start at the right
  }
  matrix.show(); // display the buffer
  // delay(delayMS);
}