MAX7219.js
function(n, symbol, dp, callback) {
    if (n < 0 || n > 7) {
      throw "Invalid digit number";
    }
    if (!(symbol in MAX7219._Font)) {
      throw "Invalid symbol string";
    }
    var byte = MAX7219._Font[symbol] | (dp ? (1 << 7) : 0);
    this._shiftOut(MAX7219._Registers["Digit" + n], byte, callback);
  }
function(n, symbol, dp, callback) {
    if (n < 0 || n > 7) {
      throw "Invalid digit number";
    }
    if (!(symbol in MAX7219._Font)) {
      throw "Invalid symbol string";
    }
    var byte = MAX7219._Font[symbol] | (dp ? (1 << 7) : 0);
    this._shiftOut(MAX7219._Registers["Digit" + n], byte, callback);
  }
function ( n , symbol , dp , callback ) { if ( n < 0 || n > 7 ) { throw "Invalid digit number" ; } if ( ! ( symbol in MAX7219 . _Font ) ) { throw "Invalid symbol string" ; } var byte = MAX7219 . _Font [ symbol ] | ( dp ? ( 1 << 7 ) : 0 ) ; this . _shiftOut ( MAX7219 . _Registers [ "Digit" + n ] , byte , callback ) ; }
Sets the symbol displayed in a digit.
For this to work properly, the digit should be in decode mode.

@param number n
The digit number, from 0 up to and including 7.
@param string symbol
The symbol do display: "0".."9", "E", "H", "L", "P", "-" or " ".
@param boolean dp
Specifies if the decimal point should be on or off.

@param function callback [optional]
Invoked once the write to the SPI device finishes.
Sets the symbol displayed in a digit . For this to work properly the digit should be in decode mode .