How to write multi-digit numbers in ASCII?

Recently I´ve started creating an android app that controls the pins of the arduino. The app sends a text value that the arduino reads in ASCII compares it to a value and turns the pin on or off. The problem is that I dont know how to write a multi-digit number such as -2 in ASCII in the code.
Here is the code:

void setup() {

pinMode(2, OUTPUT);


void loop() {


byte Data =;

if(Data == 50){ //The app sends the value 2 which is 50 in ASCII. The arduino compares it
digitalWrite(2, HIGH); //and sets the pin2 high.
if(Data == ?){ // Here the app sends the value -2. I dont know how to write it
digitalWrite(2, LOW); //in ASCII in the code so arduino can understand it because they are
} //two diferent numbers: 45 and 50.

ArduBlue.ino (527 Bytes)

You need to read numbers, not single characters like you are doing now. Learn how by reading about Serial Input Basics.