Serial.Serial.setTimeout() ;

hi.
i have 2 question.
-why there is a “L” after 2000 in Serial.setTimeout(20000L) ;

  • and How much should be written in parentheses? cuz i 'm gettin timeout error in my serial monitor.

'L' means, in this context, a long (32 bit) signed integer. The 20000 or 2000 is in milliseconds.
See https://www.arduino.cc/reference/en/language/functions/communication/stream/streamsettimeout

IMHO you would be better writing non-blocking code that is not held up waiting for a timeout.

Have a look at the examples in Serial Input Basics - simple reliable non-blocking ways to receive data. There is also a parse example to illustrate how to extract numbers from the received text.

...R

1. The syntax is:

long t = 2000;  //range of t:-2147483648 to 2147483647; allowable range: 0 to 2147483647 
Serial.setTimeout(t);   //t is in milliseconds and can not be negative

2. The above two lines could be written in the following compact form:

Serial.setTimeout(2000L);   //2000 has the data type (L for long and not Long) and meaning as stated in Step-1