Arduino+Ruby

ArduinoSide.c

int incomingByte = 0;
int ledPin = 13;

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  if (Serial.available() > 0) {
    incomingByte = Serial.read();
    for(int i= 0; i< (incomingByte - 48); i++ )
    {
      digitalWrite(ledPin, HIGH);
      delay(500);
      digitalWrite(ledPin, LOW);
      delay(500);
    }
  }
}

RubySide.rb

require 'rubygems'
require 'serialport' //gem install serialport

port = "/dev/cu.usbmodemfd121"
sp = SerialPort.new(port, 9600, 8, 1, SerialPort::NONE)
while true
  line = gets.chomp
  sp.putc line
end
sp.close