How to clean up Serial port buffer

Projects Programming
6

Your problem is that:

strcpy(buff, "");

just puts a '\0' in the first position of the buffer.

Serial.readBytesUntil('\n\r',buf, MAX);

reads the 's' and puts it in the first position of the buffer. IT DOES NOT ADD A NULL TERMINATOR. If you want the string to end after the 's' you have to put in your own terminator.

int length = Serial.readBytesUntil('\n',buf, MAX);
if (length > 0)
    buff[length] = '\0';
else
    Serial.println("No valid data found");