user2758: I'm beginning with electronics and don't have all the good reflexes yet. So here is my question:
Can I do what I did here?
can i do this http://www.movod-design.com/forum_img/canIDoThis.jpg
Do I have to add diodes between the Nano +5V and the junction point?
My goal is to have one button's state read by 2 Arduino Nano.

user1532: You don't need to add anymore components to your schematic. But you can leave some components.
Before you're adding a button to your schematic please consider first how you want to detect your signal. A logic 1 as if a button is pressed? Or logic 0 as if a button is pressed. You can do this using pull-up and pull-down resistors. These resistors should be wired like this.

(The 100Ohm resistor in an internal resistor from the MCU)
Using the pull-down resistor means that when the button is pressed you'd get a logic 1.
Using pull-up resistors means that when the button is pressed you'd get a logic 0.
When I see your schematic it seems like you're trying to make a pushbutton with pull-down resistor. Then you should wire your arduino like this.

Another option is to use the Arduino internal pull-up resistors. That way you don't have to add the 10k resistor in your schematic. And your schematic will look like this.

To use the internal pull-up resistors from the Arduino you'll need to put this in your setup(): pinMode(pin, INPUT_PULLUP); where pin should be your pin number. Please keep in mind that when you use the internal pull-up resistor a logic 0 means the button is pressed.

2758: <p>I'm beginning with electronics and don't have all the good reflexes yet. So here is my question:</p>

<p>Can I do what I did here?</p>

<p><a href="http://www.movod-design.com/forum_img/canIDoThis.jpg" rel="noreferrer">can i do this http://www.movod-design.com/forum_img/canIDoThis.jpg</a></p>

<p>Do I have to add diodes between the Nano +5V and the junction point?</p>

<p>My goal is to have one button's state read by 2 Arduino Nano.</p>
 1532: <p>You don't need to add anymore components to your schematic. But you can leave some components.</p>

<p>Before you're adding a button to your schematic please consider first how you want to detect your signal. A logic 1 as if a button is pressed? Or logic 0 as if a button is pressed. You can do this using pull-up and pull-down resistors. These resistors should be wired like this.</p>

<p><img src="https://i.stack.imgur.com/PrGmn.png" alt="pull resistor"></p>

<p>(The 100Ohm resistor in an internal resistor from the MCU)</p>

<p>Using the pull-down resistor means that when the button is pressed you'd get a logic 1.
Using pull-up resistors means that when the button is pressed you'd get a logic 0.</p>

<p>When I see your schematic it seems like you're trying to make a pushbutton with pull-down resistor. Then you should wire your arduino like this.</p>

<p><img src="https://i.stack.imgur.com/HtNNl.png" alt="pull-down button"></p>

<p>Another option is to use the Arduino internal pull-up resistors. That way you don't have to add the 10k resistor in your schematic. And your schematic will look like this.</p>

<p><img src="https://i.stack.imgur.com/uTxT0.png" alt="internal pull-up"></p>

<p>To use the internal pull-up resistors from the Arduino you'll need to put this in your setup(): pinMode(pin, INPUT_PULLUP); where pin should be your pin number. Please keep in mind that when you use the internal pull-up resistor a logic 0 means the button is pressed.</p>
