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60 lines
1.8 KiB
Markdown
60 lines
1.8 KiB
Markdown
---
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title: Buttons
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---
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# #15. Buttons
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<div class="ui segment note">
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<span class="ui ribbon label">Note</span>
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This is a web-version of a tutorial chapter embedded right into the XOD IDE.
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To get a better learning experience we recommend to install the
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<a href="/downloads/">desktop IDE</a> or start the
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<a href="/ide/">browser-based IDE</a>, and you’ll see the same tutorial there.
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</div>
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So, buttons! They could be read with a `button` node from `xod/common`
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hardware. The node makes all the work related to signal debouncing so that
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you have not to bother about it.
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The button node has a purple output pin called the `PRS`. This pin returns a new
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type of data: *boolean*.
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Boolean data can have either of two values: true or false.
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In our case, the `button` node returns a value of `false` when idle and `true`
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while the button is being pressed.
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Good news, in XOD boolean and number data types are compatible. Here are two
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rules of datacasting:
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* Boolean-to-number: if you send a boolean false to a numeric (green) input, it
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will be interpreted as a numeric 0; if you send a boolean true, it will be
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interpreted as a numeric 1.
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* Number-to-boolean: if you send any numeric value except 0 to a boolean
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(purple) input; it will be interpreted as true, and if you send 0, it will be
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interpreted as false.
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## Test circuit
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[↓ Download as a Fritzing project](./circuit.fzz)
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## How-to
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Let’s bind a button with the LED.
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1. Add a `xod/common-hardware/button` node.
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2. Set the `PORT` value.
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3. Link the `PRS` button output to the destination pin (`LUM` of the `led` in
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our example).
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Now, when you press the button the `button` node sets the `PRS` pin to `true`,
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the `led` node (`LUM` pin) interprets it as 1, and the LED turns on at full
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brightness.
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[Next lesson →](../16-logic)
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