How to clear the bytes of Serial interface in an Arduino? - c++

Question

I'm trying to interrupt the serial monitor to execute a certain function and continue with the previous function after completion of the interrupted function, my code is as bellow
#define red1 13
#define amber1 12
#define green1 11
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
pinMode(red1, OUTPUT);
pinMode(amber1, OUTPUT);
pinMode(green1, OUTPUT);
}
void Delay(int sec) {
for(int i=0;i<sec;i++){
if (Serial.available())
{
Button();
break;
}
delay(1);
}
}
void Light()
{
digitalWrite(red1,HIGH);
Delay(5000);
digitalWrite(red1,LOW);
digitalWrite(amber1,HIGH);
Delay(5000);
digitalWrite(amber1,LOW);
}
void Button()
{
digitalWrite(red1,LOW);
digitalWrite(amber1,LOW);
digitalWrite(green1,HIGH);
delay(1000);
digitalWrite(green1,LOW);
}
void loop()
{
Light();
}
Whenever I enter a value in serial monitor Button() function is executed, it should end as soon as function completes due to a break, but this function keeps repeating continuously? How can I fix this such that whenever a serial monitor is interrupted, Button() is executed onetime and then continues with Light().
I tried using a break but the serial interface buffer is not cleared so its keep continuing this function also it exits if loop, so I tried using return
void Delay(int sec) {
for(int i=0;i<sec;i++){
if (Serial.available())
{
Button();
return;
}
delay(1);
}
}
the same thing happens
the function doesn't exit it keeps repeating the same since the serial interface is not cleared from an earlier encounter, I could've used serial.available in void loop() but whenever Arduino is at delay function its sleeping so it doesn't read a serial interrupter, so I created separate Delay()
so how can I change the code to end this function and go back to Light()

Answer 1

but the serial interface buffer is not cleared
Then you have to clear it:
while (Serial.available())
Serial.read(); // remove 1 character