Bit mapping for 8*8 LED Matrix

This post show how to map char to bitmap for 8*8 LED Matrix. In the example code, only 5 char 'A'...'E' are implemented. The char in str[] will be displayed character-by-character.

/*
 *  Modify from Row-Column Scanning an 8x8 LED matrix tutorial
 *  http://arduino-er.blogspot.com/
 */


// 2-dimensional array of row pin numbers:
const int row[8] = {
  2, 7, 19, 5, 13, 18, 12, 16
};

// 2-dimensional array of column pin numbers:
const int col[8] = {
  6, 11, 10, 3, 17, 4, 8, 9
};

// 2-dimensional array of pixels:
int pixels[8][8];

int count = 1000;

char str[] = "EDCBA";
int strLen = sizeof(str);
int ptrChar = 0;


typedef bool charMapType[8][8];

const charMapType charDummy = {
  {0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0}
};

const charMapType charA = {
  {0, 0, 0, 1, 1, 0, 0, 0},
  {0, 0, 0, 1, 1, 0, 0, 0},
  {0, 0, 1, 0, 0, 1, 0, 0},
  {0, 0, 1, 0, 0, 1, 0, 0},
  {0, 1, 1, 1, 1, 1, 1, 0},
  {0, 1, 0, 0, 0, 0, 1, 0},
  {1, 1, 0, 0, 0, 0, 1, 1},
  {1, 0, 0, 0, 0, 0, 0, 1}
};

const charMapType charB = {
  {1, 1, 1, 1, 1, 1, 0, 0},
  {0, 1, 0, 0, 0, 0, 1, 0},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {0, 1, 1, 1, 1, 1, 1, 0},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {0, 1, 0, 0, 0, 0, 1, 0},
  {1, 1, 1, 1, 1, 1, 0, 0}
};

const charMapType charC = {
  {0, 1, 1, 1, 1, 1, 1, 0},
  {1, 0, 0, 0, 0, 0, 0, 1},
  {1, 0, 0, 0, 0, 0, 0, 1},
  {1, 0, 0, 0, 0, 0, 0, 0},
  {1, 0, 0, 0, 0, 0, 0, 0},
  {1, 0, 0, 0, 0, 0, 0, 1},
  {1, 0, 0, 0, 0, 0, 0, 1},
  {0, 1, 1, 1, 1, 1, 1, 0}
};

const charMapType charD = {
  {1, 1, 1, 1, 1, 1, 1, 0},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {0, 1, 0, 0, 0, 0, 0, 1},
  {1, 1, 1, 1, 1, 1, 1, 0}
};

const charMapType charE = {
  {1, 1, 1, 1, 1, 1, 1, 1},
  {0, 1, 0, 0, 0, 0, 0, 0},
  {0, 1, 0, 0, 0, 0, 0, 0},
  {0, 1, 1, 1, 1, 1, 1, 0},
  {0, 1, 0, 0, 0, 0, 0, 0},
  {0, 1, 0, 0, 0, 0, 0, 0},
  {0, 1, 0, 0, 0, 0, 0, 0},
  {1, 1, 1, 1, 1, 1, 1, 1}
};


const charMapType *charMap[5] = {&charA, &charB, &charC, &charD, &charE};

void setup() {
  // initialize the I/O pins as outputs
  // iterate over the pins:
  for (int thisPin = 0; thisPin < 8; thisPin++) {
    // initialize the output pins:
    pinMode(col[thisPin], OUTPUT);
    pinMode(row[thisPin], OUTPUT);
    // take the col pins (i.e. the cathodes) high to ensure that
    // the LEDS are off:
    digitalWrite(col[thisPin], HIGH);
  }

  
  //setupScreen();
  setupChar();

}

void loop() {

  // draw the screen:
  refreshScreen();
  
  if(count-- == 0){
    count = 1000;
    setupChar();
  }

}

void setupChar(){
  char c = str[ptrChar];
  int offset = c - 'A';
  
  const charMapType *cMap = charMap[offset];
  //charMapType *cMap = &charDummy;
  
  for (int x = 0; x < 8; x++) {
    for (int y = 0; y < 8; y++) {
      bool v = (*cMap)[x][y];
      
      if(v){
        pixels[x][y] = LOW;
      }else{
        pixels[x][y] = HIGH;
      }
    }
  }
  
  ptrChar++;
  if(ptrChar>=strLen-1){
    ptrChar = 0;
  }

}

void refreshScreen() {
  // iterate over the rows (anodes):
  for (int thisRow = 0; thisRow < 8; thisRow++) {
    // take the row pin (anode) high:
    digitalWrite(row[thisRow], HIGH);
    // iterate over the cols (cathodes):
    for (int thisCol = 0; thisCol < 8; thisCol++) {
      // get the state of the current pixel;
      int thisPixel = pixels[thisRow][thisCol];
      // when the row is HIGH and the col is LOW,
      // the LED where they meet turns on:
      digitalWrite(col[thisCol], thisPixel);
      // turn the pixel off:
      if (thisPixel == LOW) {
        digitalWrite(col[thisCol], HIGH);
      }
    }
    // take the row pin low to turn off the whole row:
    digitalWrite(row[thisRow], LOW);
  }
}