user67743: The idea is to connect more than 1 arduino slave to master as shown in schamatic

simulate this circuit – Schematic created using CircuitLab
The problem is TX slave can not just combine to master RX.
It need to done some trick like tri-state buffer to make slave TX one at time.
Anyway, avr port can config as tristate buffer.
(Q1)Is there any software solution to done this?
Second If I connnect TX to RX for half-duplex communication (using 1 data line). How to make Rx stop listenning to its self while transmiting data?

user4143: You can do it with two diodes and a resistor:

simulate this circuit – Schematic created using CircuitLab
You'll still have to implement some system to prevent collisions, but electrically that will be sound.

67743: <p>The idea is to connect more than 1 arduino slave to master as shown in schamatic</p>

<p><img src="https://i.stack.imgur.com/WtU2Z.png" alt="schematic" /></p>

<p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fWtU2Z.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup>
The problem is TX slave can not just combine to master RX.
It need to done some trick like tri-state buffer to make slave TX one at time.
Anyway, avr port can config as tristate buffer.
(Q1)Is there any software solution to done this?
Second If I connnect TX to RX for half-duplex communication (using 1 data line). How to make Rx stop listenning to its self while transmiting data?</p>
 4143: <p>You can do it with two diodes and a resistor:</p>

<p><img src="https://i.stack.imgur.com/YgEq7.png" alt="schematic" /></p>

<p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fYgEq7.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup></p>
<p>You'll still have to implement some system to prevent collisions, but electrically that will be sound.</p>
