Get the number of bytes (characters) available for reading from the serial port. This is data that's already arrived and stored in the serial receive buffer (which holds 64 bytes). available() inherits from the Stream utility class.

Serial.available() Arduino Mega only: Serial1.available() Serial2.available() Serial3.available()

none

the number of bytes available to read

int incomingByte = 0;   // for incoming serial data
 
void setup() {
        Serial.begin(9600);     // opens serial port, sets data rate to 9600 bps
}
 
void loop() {
 
        // send data only when you receive data:
        if (Serial.available() > 0) {
                // read the incoming byte:
                incomingByte = Serial.read();
 
                // say what you got:
                Serial.print("I received: ");
                Serial.println(incomingByte, DEC);
        }
}

Arduino Mega example:

void setup() {
  Serial.begin(9600);
  Serial1.begin(9600);
 
}
 
void loop() {
  // read from port 0, send to port 1:
  if (Serial.available()) {
    int inByte = Serial.read();
    Serial1.print(inByte, BYTE); 
 
  }
  // read from port 1, send to port 0:
  if (Serial1.available()) {
    int inByte = Serial1.read();
    Serial.print(inByte, BYTE); 
  }
}

• begin()
• end()
• available()
• read()
• peek()
• parseInt()
• flush()
• print()
• println()
• write()
• SerialEvent()
• Stream.available()

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