I have a Uno program and I can transfer data to Processing using println. In Processing bufferUntil('\n') interprets the ln as \n, stops buffering, and reads the string until the next '\n'. I would like to use something other than ln to trigger Processing. That way I can use Serial Monitor in the Uno to see serial data when Processing is not running at the same time.

I have searched the net but have not found the technique to use something other than ln. Thanks.

  • ln? You mean \n aka new line character?
    – gre_gor
    Jun 25, 2017 at 21:18
  • 2
    Sounds like you want 2 programs monitoring the same serial port on the PC. What OS are you using? The question is not very clear.
    – 001
    Jun 26, 2017 at 3:06

1 Answer 1


If I understand your question (which is not certain):

  • Pick a different "trigger" byte that you won't be sending in your messages. Maybe TAB?
  • In your "Processing" program, use: port.bufferUntil(TRIGGER);
  • In your Arduino sketch, rather than println, use print to send both your data and the trigger byte: Serial.print(your_message); Serial.print(TRIGGER);

Note that sending binary data will cause this to fail when the data uses the trigger byte.

From: https://www.arduino.cc/en/Serial/Println The println() method sends your output then a CR and NL. And it seems bufferUntil() takes a character on which to trigger: https://processing.org/reference/libraries/serial/Serial_bufferUntil_.html

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