Displaying byte table to LED grid

Projects Programming
1

I created a program to display a scrolling text (variable width) on an LED grid (8x32). The code below displays the message variable content of "Z[]^_ayz", however, the LED grid displays "Z[\^_abz". The abz is due to the shift of the table as if a row is missing, but ] exists in the table.

I tried displaying everything in the Alphabet table and for some reason only ] is missing.

Any idea why only ] is missing would be appreciated.

Arduino Uno R3 in case it matters.

/*
Define fonts and show scrolling text
*/
#include <FastLED.h>
#define LED_PIN 7
#define NUM_ROWS 8
#define NUM_COLS 32
#define NUM_LEDS NUM_ROWS * NUM_COLS
#define BRIGHTNESS 2

const byte Alphabet[58][9] PROGMEM = {
  {B00000100,B00001010,B00010001,B00010001,B00011111,B00010001,B00010001,B00000000, 5}, // A
  {B00011110,B00010001,B00010001,B00011110,B00010001,B00010001,B00011110,B00000000, 5}, // B
  {B00001110,B00010001,B00010000,B00010000,B00010000,B00010001,B00001110,B00000000, 5}, // C
  {B00011110,B00010001,B00010001,B00010001,B00010001,B00010001,B00011110,B00000000, 5}, // D
  {B00011111,B00010000,B00010000,B00011100,B00010000,B00010000,B00011111,B00000000, 5}, // E
  {B00011111,B00010000,B00010000,B00011100,B00010000,B00010000,B00010000,B00000000, 5}, // F
  {B00001110,B00010001,B00010000,B00010111,B00010001,B00010001,B00001110,B00000000, 5}, // G
  {B00010001,B00010001,B00010001,B00011111,B00010001,B00010001,B00010001,B00000000, 5}, // H
  {B00011111,B00000100,B00000100,B00000100,B00000100,B00000100,B00011111,B00000000, 5}, // I
  {B00001111,B00000001,B00000001,B00000001,B00000001,B00010001,B00001110,B00000000, 5}, // J
  {B00010001,B00010010,B00010100,B00011000,B00010100,B00010010,B00010001,B00000000, 5}, // K
  {B00010000,B00010000,B00010000,B00010000,B00010000,B00010000,B00011111,B00000000, 5}, // L
  {B01000001,B01100011,B01010101,B01001001,B01000001,B01000001,B01000001,B00000000, 7}, // M
  {B00010001,B00011001,B00011001,B00010101,B00010011,B00010011,B00010001,B00000000, 5}, // N
  {B00001110,B00010001,B00010001,B00010001,B00010001,B00010001,B00001110,B00000000, 5}, // O
  {B00011110,B00010001,B00010001,B00011110,B00010000,B00010000,B00010000,B00000000, 5}, // P
  {B00001110,B00010001,B00010001,B00010001,B00010101,B00010010,B00001101,B00000000, 5}, // Q
  {B00011110,B00010001,B00010001,B00011110,B00010100,B00010010,B00010001,B00000000, 5}, // R
  {B00001110,B00010001,B00010000,B00001110,B00000001,B00010001,B00001110,B00000000, 5}, // S
  {B00011111,B00000100,B00000100,B00000100,B00000100,B00000100,B00000100,B00000000, 5}, // T
  {B00010001,B00010001,B00010001,B00010001,B00010001,B00010001,B00001110,B00000000, 5}, // U
  {B00010001,B00010001,B00010001,B00001010,B00001010,B00000100,B00000100,B00000000, 5}, // V
  {B01000001,B01000001,B01000001,B01001001,B01010101,B01100011,B01000001,B00000000, 7}, // W
  {B00010001,B00010001,B00001010,B00000100,B00001010,B00010001,B00010001,B00000000, 5}, // X
  {B00010001,B00010001,B00010001,B00001010,B00000100,B00000100,B00000100,B00000000, 5}, // Y
  {B00011111,B00000001,B00000010,B00000100,B00001000,B00010000,B00011111,B00000000, 5}, // Z
  {B00000111,B00000100,B00000100,B00000100,B00000100,B00000100,B00000100,B00000111, 3}, // [
  {B00010000,B00001000,B00001000,B00000100,B00000100,B00000010,B00000010,B00000001, 5}, // \ 
  {B00000111,B00000001,B00000001,B00000001,B00000001,B00000001,B00000001,B00000111, 3}, // ]
  {B00000010,B00000101,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000, 3}, // ^
  {B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00001111, 4}, // _
  {B00000010,B00000011,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000, 3}, // `
  {B00000000,B00000000,B00000110,B00000001,B00000111,B00001001,B00000111,B00000000, 4}, // a
  {B00001000,B00001000,B00001000,B00001110,B00001001,B00001001,B00001110,B00000000, 4}, // b
  {B00000000,B00000000,B00000110,B00001001,B00001000,B00001001,B00000110,B00000000, 4}, // c
  {B00000001,B00000001,B00000001,B00000111,B00001001,B00001001,B00000111,B00000000, 4}, // d
  {B00000000,B00000000,B00000110,B00001001,B00001111,B00001000,B00000110,B00000000, 4}, // e
  {B00000110,B00001001,B00001000,B00011110,B00001000,B00001000,B00001000,B00000000, 5}, // f
  {B00000000,B00000000,B00000110,B00001001,B00001001,B00000111,B00000001,B00000110, 4}, // g
  {B00001000,B00001000,B00001000,B00001110,B00001001,B00001001,B00001001,B00000000, 4}, // h
  {B00000000,B00000001,B00000000,B00000001,B00000001,B00000001,B00000001,B00000000, 1}, // i
  {B00000000,B00000001,B00000000,B00000001,B00000001,B00000001,B00001001,B00000110, 4}, // j
  {B00001000,B00001000,B00001001,B00001010,B00001100,B00001010,B00001001,B00000000, 4}, // k
  {B00000001,B00000001,B00000001,B00000001,B00000001,B00000001,B00000001,B00000000, 1}, // l
  {B00000000,B00000000,B00011010,B00010101,B00010101,B00010001,B00010001,B00000000, 5}, // m
  {B00000000,B00000000,B00001110,B00001001,B00001001,B00001001,B00001001,B00000000, 4}, // n
  {B00000000,B00000000,B00000110,B00001001,B00001001,B00001001,B00000110,B00000000, 4}, // o
  {B00000000,B00000000,B00000110,B00001001,B00001001,B00001110,B00001000,B00001000, 4}, // p
  {B00000000,B00000000,B00000110,B00001001,B00001001,B00000111,B00000001,B00000001, 4}, // q
  {B00000000,B00000000,B00000110,B00001001,B00001000,B00001000,B00001000,B00000000, 4}, // r
  {B00000000,B00000000,B00000111,B00001000,B00000110,B00000001,B00001110,B00000000, 4}, // s
  {B00000000,B00000000,B00000010,B00000111,B00000010,B00000010,B00000011,B00000000, 3}, // t
  {B00000000,B00000000,B00001001,B00001001,B00001001,B00001001,B00000111,B00000000, 4}, // u
  {B00000000,B00000000,B00010001,B00010001,B00010001,B00001010,B00000100,B00000000, 5}, // v
  {B00000000,B00000000,B00010001,B00010001,B00010101,B00010101,B00001010,B00000000, 5}, // w
  {B00000000,B00000000,B00010001,B00001010,B00000100,B00001010,B00010001,B00000000, 5}, // x
  {B00000000,B00000000,B00001001,B00001001,B00001001,B00000111,B00000001,B00000110, 4}, // y
  {B00000000,B00000000,B00001111,B00000001,B00000110,B00001000,B00001111,B00000000, 4}  // z
};

CRGB leds[NUM_LEDS];
// String message = "ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz";
String message = "Z[\\]^_`ayz";

void setup() {
  Serial.begin(9600);
  Serial.println("Hello World!");
  FastLED.addLeds<WS2812B, LED_PIN, GRB>(leds, NUM_LEDS);
  FastLED.setBrightness(BRIGHTNESS);
  // writeMessage(message, 0, CRGB::White);
  for(int position = 0; position < message.length(); position++) {
    char letter = message.charAt(position);
    Serial.print(letter);
  }
  Serial.println();
}

void loop() {
  int l = message.length() * 8;
  for(int i = NUM_COLS; i > -l; i--) {
    writeMessage(message, i, CRGB::White);
    FastLED.delay(200);
  }
}

void writeMessage(String message, int column, CRGB color) {
  // black out the board for the message
  for(unsigned char r = 0; r < NUM_ROWS; r++) {
    for(unsigned char c = 0; c < NUM_COLS; c++) {
      leds[ledNum(r, c)] = CRGB::Black;
    }
  }
  for(int position = 0; position < message.length(); position++) {
    int letter = message.charAt(position) - 65; // 65 is 'A'
    byte width = 0;
    if(letter >= 0 && letter < 58) {
      width = pgm_read_byte_near(*Alphabet + letter*9 + 8);
      for(unsigned char r = 0; r < 8; r++) {
        for(unsigned char c = 0; c < width; c++) {
          // this loop pulls each bit off the byte one at a time
          if((pgm_read_byte_near(*Alphabet + letter*9 + r) >> c & 1) == 1) {
            int col = column + width - c - 1; // not sure why this is off by one...
            if(col >= 0 && col < NUM_COLS)
              leds[ledNum(r, col)] = CRGB::Red;
          }
        }
      }
    }
    column += width + 1; // move over for next letter (plus a space)
    if(column > NUM_COLS)
      break; // Too far to the right for any pixel of the next letter to appear
  }
  FastLED.show();
}

int ledNum(int row, int col) {
  if(col % 2 == 1) {
    row = NUM_ROWS - row - 1;
  }
  return col * NUM_ROWS + row;
}
2

Show the output (send to Serial.print(); ) so I don't have to ask if "tick" or "waca" is in there. : )

3

Hello World!
Z[\]^_`ayz

4 
  {B00010000, B00001000, B00001000, B00000100, B00000100, B00000010, B00000010, B00000001, 5}, // \

Remove the \ at the end of the line, it tells the compiler that the comment is continued on the next line, so you are losing a line out of the table.

2 Likes
5

Ok, that fixed that problem, but that seems like a bug in the IDE 2.0.3. I had originally put '// \' as the comment but saw the next line change color, so I added a space '// \ ' so it changed back then completely forgot about it, but apparently the compiler still didn't like it.

Any simple way to leave the \ in there (other than putting words after it)?

6 

   *****
       *
      *
     *
    *
   *
   *****


     ***
     *
     *
     *
     *
     *
     *
     ***

   *
    *
    *
     *
     *
      *
      *
       *

      *
     * *














    ****

      *
      **









     **
       *
     ***
    *  *
     ***
7

There has to be a non-whitespace character after the backslash, or the compiler will concatenate the next line onto the current one.

8

Try
// '\'

9

Any non-whitespace, ok.

10

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