// readOneChar.ino
// Reads one char cmds from Serial
// https://www.forward.com.au/pfod/ArduinoProgramming/SoftwareSolutions/index.html
// Pros: Extremely Simple, Non-blocking and Robust
// Cons: Nothing really. You can do a lot with one char cmds (A..Z,a..z,0..9) plus symbols

void setup() {
  Serial.begin(9600);
  for (int i = 10; i > 0; i--) {
    Serial.print(' '); Serial.print(i);
    delay(500);
  }
  Serial.println();
}

void loop() {
  int c = Serial.read(); // note read() returns an int
  if (c != -1) { // read() return -1 if there is nothing to be read. 
    // got a char handle it
    Serial.println((char)c); // need to cast to char c to print it otherwise you get a number instead
  }
}