Diffrence between running once and infinite

Question

const int ledPin = 12;
void setup(){
 pinMode(ledPin, OUTPUT);
 Serial.begin(9600);
}
void loop(){
 if (Serial.available()) {
 light(Serial.read() – '0');
 }
 delay(500);
}
void light(int n){
 for (int i = 0; i < n; i++) {
 digitalWrite(ledPin, HIGH);
 delay(100);
 digitalWrite(ledPin, LOW);
 delay(100);
 }
}

by Oscar Liang

awesome little piece of code which taught me how to setup connection by serial. yet one part I don't understand fully. Why does this line:

light(Serial.read() – '0');

make the code run once, and this line an infinite times.

light(Serial.read());

has this something to do with binary? I don't get why subtracting the string 0 would run the code once.

Thanks in Advance!

Answer 1

Serial.read() -'0'

Such code is often used to convert a character to a digit (e.g. int).

Like if the character is '2', than '2' - '0' = ascii 50 - ascii 48 = 2

However, if you use

Serial.read()

the value will be 50 instead of 2.... maybe looping 50 times (or 48 to 58, for values 0 to 9) will give you the impression it runs infinite?

• Anton van der Wel: oh wow Thank you, so that is just a way to convert to a int. Never knew that!
• Michel Keijzers: Yes, it is a way to convert one digit (so a character from '0' to '9') to an integer. Nb if this answer is good, consider upvoting and accepting it as your answer.
• Anton van der Wel: cant upvote yet. I don't have enough rep, but you will get it in the end :)
• Michel Keijzers: Thanks for accepting. No problem (geen probleem). Enjoy programming!