Example NodeBots (JavaScript) code for MakeBlock mBot LED Matrix

led_matrix.js

/*
 * Titan Micro Electronics TM1640: 16 x 8 LED driver datasheet (Chinese)
 * https://dl.dropboxusercontent.com/u/8663580/TM1640.pdf
 *
 * TODO: Turn this code into a module and use it in "nodebots.js".
 * TODO: Make all functions available to the REPL.
 */

var five  = require('johnny-five');
var board = five.Board();

// Define Data Command Parameters

var MODE_ADDRESS_AUTO_ADD_1 = 0x40;
var MODE_PERMANENT_ADDRESS  = 0x44;
var WIDTH  = 16;
var HEIGHT =  8;

board.on('ready', function() {
  var pin_clock = five.Pin({
    pin:  14,
    mode: this.io.MODES.OUTPUT,
  });

  var pin_data = five.Pin({
    pin:  15,
    mode: this.io.MODES.OUTPUT,
  });

  console.log('Board ready');

  var screen = {
    pin_clock: pin_clock, pin_data: pin_data, matrix: new Buffer(16)
  };

  write_byte(pin_clock, pin_data, MODE_ADDRESS_AUTO_ADD_1);  // Set mode
  write_byte(pin_clock, pin_data, 0x8c);                     // Set brightness ?
  clear_screen(screen);

  if (true) {
    draw_character(screen,  1, 0, 'G', state);
    draw_character(screen,  7, 0, 'o', state);
    draw_character(screen, 13, 0, '!', state);
    write_screen(screen);
  }
  else {
    screen.matrix = new Buffer([     // Checkerboard
      0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55,
      0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55
    ]);
    write_screen(screen);
  }
  clear_screen(screen);

  var state = false;

  setInterval(function() {
    state = ! state;

    if (true) {                                 // Face ?
      draw_rectangle(screen, 0, 0, WIDTH, HEIGHT, state);
      draw_circle(screen,  5, 3, 1, state);
      draw_circle(screen, 10, 3, 1, state);
      draw_hline(screen,   7, 5, 2, state);
    }
    else {                                      // X marks the spot !
      draw_line(screen, 0, 0,          WIDTH - 1, HEIGHT - 1, state);
      draw_line(screen, 0, HEIGHT - 1, WIDTH - 1, 0,          state);
    }

//  invert_screen(screen);

    write_screen(screen);
  }.bind(this), 1000);

  this.repl.inject({
    test: function() {
      console.log('test');
    }
  });
});

function write_byte(pin_clock, pin_data, buffer) {
  pin_clock.high();  pin_data.low();

  for (var bit = 0;  bit < 8; bit ++) {
    pin_clock.low();
    pin_data.write(buffer & 0x01);
    pin_clock.high();
    buffer = buffer >> 1;
  }

  pin_clock.low();   pin_data.low();
  pin_clock.high();  pin_data.high();
}

function write_bytes_to_address(pin_clock, pin_data, address, buffer) {
  address = address | 0xc0;

  pin_clock.high();  pin_data.low();

  for (var bit = 0;  bit < 8; bit ++) {
    pin_clock.low();
    pin_data.write(address & 0x01);
    pin_clock.high();
    address = address >> 1;
  }
  for (var byte = 0;  byte < buffer.length;  byte ++) {
    var data = buffer[byte];

    for (bit = 0; bit < 8; bit ++) {
      pin_clock.low();
      pin_data.write(data & 0x01);
      pin_clock.high();
      data = data >> 1;
    }
  }

  pin_clock.low();   pin_data.low();
  pin_clock.high();  pin_data.high();
}

function write_screen(screen) {
  write_bytes_to_address(screen.pin_clock, screen.pin_data, 0, screen.matrix);
}

function clear_screen(screen, value) {  // value = 0xff for all LEDS on
  if (typeof(value) === 'undefined') value = 0;
  screen.matrix.fill(value);
  write_screen(screen);
}

function invert_screen(screen) {
  for (var index = 0;  index < screen.matrix.length;  index ++) {
    screen.matrix[index] = screen.matrix[index] ^ 0xff;
  }
}

function draw_point(screen, column, row, value) {
  var bit  = (typeof(value) === 'undefined')  ?  1  :  value;
  var mask = 0xff ^ (1 << row);
  screen.matrix[column] = screen.matrix[column] & mask | (bit << row);

// TODO: This should work and would be much more efficient !
//write_bytes_to_address(
//  screen.pin_clock, screen.pin_data, column, new Buffer(screen.matrix[column])
//);
}

function draw_hline(screen, column, row, length, value) {
  for (var index = column;  index < column + length;  index ++) {
    draw_point(screen, index, row, value);
  }

// TODO: More efficient to write_bytes_to_address() for only changed columns !
}

function draw_vline(screen, column, row, length, value) {
  var bit  = (typeof(value) === 'undefined')  ?  1  :  value;
  var byte = (Math.pow(2, length) - 1) << row;
  var mask = 0xff ^ byte;
  if (bit === false) byte = 0;
  screen.matrix[column] = screen.matrix[column] & mask | byte;

// TODO: This should work and would be much more efficient !
//write_bytes_to_address(
//  screen.pin_clock, screen.pin_data, column, new Buffer(screen.matrix[column])
//);
}

// Bresenham's line algorithm

function draw_line(screen, column0, row0, column1, row1, value) {
  var column_delta = Math.abs(column1 - column0);
  var row_delta    = Math.abs(row1    - row0);

  var column_increment = column0 < column1 ? 1 : -1;
  var row_increment    = row0    < row1    ? 1 : -1;

  var error = (column_delta > row_delta ? column_delta : -row_delta) / 2;

  while (true) {
    draw_point(screen, column0, row0, value);

    if (column0 === column1  &&  row0 === row1) break;

    var error2 = error;

    if (error2 > -column_delta) {
      error   -= row_delta;
      column0 += column_increment;
    }

    if (error2 < row_delta) {
      error += column_delta;
      row0  += row_increment;
    }
  }
}

function draw_rectangle(screen, row, column, width, height, value) {
  draw_hline(screen, column, row,              width,  value);
  draw_hline(screen, column, row + height - 1, width,  value);
  draw_vline(screen, column, row,              height, value);
  draw_vline(screen, column + width - 1, row,  height, value);
}

function fill_rectangle(screen, column, row, width, height, value) {
  for (var index = 0;  index < width;  index ++) {
    draw_vline(screen, column + index, row, height, value);
  }
}

// Bresenham's line algorithm extended for circles

function draw_circle(screen, column, row, radius, value) {
  var x = radius, y = 0;
  var radiusError = 1 - x;

  while (x >= y) {
    draw_point(screen, -y + column, -x + row, value);
    draw_point(screen,  y + column, -x + row, value);
    draw_point(screen, -x + column, -y + row, value);
    draw_point(screen,  x + column, -y + row, value);
    draw_point(screen, -x + column,  y + row, value);
    draw_point(screen,  x + column,  y + row, value);
    draw_point(screen, -y + column,  x + row, value);
    draw_point(screen,  y + column,  x + row, value);
    y++;

    if (radiusError < 0) {
      radiusError += 2 * y + 1;
    }
    else {
      x --;
      radiusError += 2 * (y - x + 1);
    }
  }
}

function fill_circle(screen, column, row, radius, value) {
  var x = radius, y = 0;
  var radiusError = 1 - x;

  while (x >= y) {
    draw_line(screen, -y + column, -x + row, y + column, -x + row, value);
    draw_line(screen, -x + column, -y + row, x + column, -y + row, value);
    draw_line(screen, -x + column,  y + row, x + column,  y + row, value);
    draw_line(screen, -y + column,  x + row, y + column,  x + row, value);
    y++;

    if (radiusError < 0) {
      radiusError += 2 * y + 1;
    }
    else {
      x --;
      radiusError+= 2 * (y - x + 1);
    }
  }
}

// Thanks Suz (@noopkat) ... https://github.com/noopkat/oled-font-5x7 !

var font = require('./vendor/oled-font-5x7/oled-font-5x7');

function draw_character(screen, column, row, character, value) {
  var lookup   = index = font.lookup.indexOf(character) * 5;
  var fontData = font.fontData.slice(lookup, lookup + 5);

  for (var index = 0;  index < fontData.length;  index ++) {
    screen.matrix[column + index] = fontData[index] << 1;
  }
}

Now includes fill_circle() and draw_character()

Note: You will need to ...
mkdir vendor
cd vendor
git clone https://github.com/noopkat/oled-font-5x

Brilliant - will look at how we get this back into the main side of J5 as well in LED matrix

The prototype code in this Gist has been made into a proper NodeBot driver and moved to https://github.com/geekscape/nodebot_ai ... @ajfisher let's continue the discussion over there (as GitHub issues ?).