want to do this via the RX / TX though I do not know what will work best with multiple units in the end.
Serial.print('<'); // start markerSerial.print(value1);Serial.print(','); // comma separatorSerial.print(value2);Serial.println('>'); // end marker
for now I only use the mega with lcd as a thermostat for the heating.and UNO for controlling the heating itself. so I have to be able to switch twice with the MEGA ("on / off and" high / low ") via RX / TX on the UNO and display an error message from the UNO on the MEGA later on, it must also show disturbances of other arduinos .finally it becomes a large operating system with no less than 5 arduinos. most a mega
Well there is nothing about sending.
but I also see nothing in it what reacts to the received data. Beyond that it is shown on the serial monitor.
Did you read Reply #1 carefully? I wrote it on the assumption that you would.I thought I should leave a little bit of the work for you.If you just want someone to write a program for you please ask in the Gigs and Collaborations section of the Forum and be prepared to pay....R
1st question:char mystr  = "Hello"; // String datawhat is the 5 connected to? the number of letters of HELLO?
char mystr  = "Hello";
2nd question:can i of this:Serial.println (mystr); // Print data on Serial Monitor
unpunished to make something of:if (mystr) = on else if (mystr) = off else if ...............
i have this in the mega:
so your code looks like this
is to big to copy/paste