11512991203:
When Leonardo communicate with grbl ,should isolate the rx line with pc. But i can't understand how to do that.
I don't know either - because AFAIK the data from the PC to the Rx pin on the GRBL Arduino goes through the Arduino circuit board.
However, even if you could isolate that signal you have to ask yourself if it would be wise to do so. What would happen if the PC needed to send some data?
If other GRBL users are doing what you want to do then you should be asking questions of them. This Forum is primarily about writing your own Arduino programs.
Leonardo is not must be used.
I don't understand.
...R